Wood Fired Pool Heater

[Pool-newb]

First I want to thank everyone here with the advice for maintaining a pool. I have been able to rescue mine from a horribly stained muck swamp to a clean cool refreshing pool. I hope my comments here can help someone on the brink of a decision about a heater.

I recently Had 8 large hardwood trees removed from my yard and I kept the wood so I thought that instead of paying for gas to heat the pool, I bought a wood fired pool heater.

I've had it for about a week now and I wanted to share my so far limited experiences.

Finding such a thing on the web was not easy. There are only a few available and I was only able to find one that sits outside the water There are "hot tub" wood-fired water heaters that sit completely in the water except for the smoke stack and wood feeding box but I didn't want to sacrifice any of my pool for this as it's already too small, and I didn't want the mess around the pool either.

So I called the guys at ExtendaSwim - the only other manufacturer I could find - and ordered one.

The individual taking my call suggested I order the middle sized heater even though the smallest heater was more appropriate for my pool. Apparently they were doing a redesign of the smallest one and the delivery time would have been fairly long. I followed his advice but more because the wood I have is partially in large pieces, and also because I wanted to be able to heat quickly and shut it down. I live in a typical subdivision of smallish lots and I was (and still am) concerned about the effects of smoke in the neighborhood.

The heater arrived on Friday afternoon about a week and a half after I ordered it. The delivery was with a huge truck and they dropped it in front of my garage. On the pallet it weighed around 450 lbs but removing all the brick, doors and spare parts got it down to probably three hundred. Using a hand truck, a friend and I were able to move it around the house to near the final position. From there I made a simple cement block base for it and was able to maneuver it the final few feet up onto the base myself.

Installing was very simple - water in and water out connections. The stove is designed for 1.5" plumbing but I have 2" plumbing above ground so it took a few trips to the DIY store to get all the connectors and adapters, and the gluing took a few hours but once that was finished I was able to start a fire and admire my handiwork.

===> Performance information:

The installation was completed and the first fire was lit at about 4 AM on on Saturday 26 Apr.

On 25 Apr at 9:46, the temp was 16.8°C/62.2°F, not using solar cover.

On 25 Apr at 14:55 the temp was 19.7°/67.5°C, not using solar cover (it was a warm day so lots of variability with sun alone)

On 26 Apr at about 4 am the fire was lit, then I slept till about 11.

On 26 Apr at 11:03 the temp was 19.0°C/66.2°F, not using solar cover

On 26 Apr at 12:06 the temp was 20.7°C/69.7°F, started using solar cover now

On 27 Apr at 14:05 the temp was 24.5°C/76.1°F, using solar cover except when swimming (about 1 hr/day)

On 30 Apr at 16:25 the temp was 28.3°C/ 82.9°f, " " " (Was this warm sooner, I just didn't record it.)

It also warmed up to about 30°C/86°F but I did not record it, and by then I was tapering off adding the wood.

I have now let the fire die out and the heater is once again cold. The pool seems to maintain about 28°C without adding heat but today is also our first "cool" (23°C) since starting this. I'll see how the temp holds.

My take aways are:

- To go from really cold to toasty warm needs about 1.5 - 2 days constant burning

- I always use the solar cover. The pool gets very little direct sun but even the cheap cover keeps the heat in well

- I have several types of wood and the type and size of wood is directly related to how often it needs feeding, how it is fed, how much smoke it produces and how much it warms the water. Blanket statements about performance are difficult to make without considering these factors.

- I will probably be able to use it only very intermittently in warm weather but may be able to swim year round if constantly fed in winter.

===> Concept and design comments

While the heater works as advertised and heats the pool well, I found it to be lacking in efficiency.

- They provide an 8" X 24" chimney pipe with a magnetic thermometer, and recommend the chimney temperature be maintained at 250°F to 475°F. Wow, I'd much rather that this heat be added to the water and not be sent up and 8" chimney!

Most of the box is insulated but the door and draft control are not. Here again is a large area of heat loss that I would much rather see going into the water.

- The provided chimney is just a gaping hole. While there is a facility for adjusting the air intake on the front of the box, I would have found it appropriate to add a flu damper, (I am intending to investigate doing this myself). This would keep some of the heat in the box during the startup phase, and could be used to help extinguish the fire if no more heat was needed and the wood should be saved.

- The air intake occurs exclusively at the front. It is a large metal flap that can be locked in one of three positions or opened fully. While this can certainly provide enough air for the fire, having the air come from only one side tends to starve the parts of the fire towards the rear of the box. I would have appreciated having an adjustable air intake that also routes part of the air to the rear of the fire, perhaps even with an attachment for a hand driven or electric powered air pump. In fact, I used an electric air mattress inflation pump to stoke a fire that had been producing thick smoke for too long.

Another change I'd like to see made to the air intake is to have it more precisely and easily adjustable. The current three position latch requires fiddling and doesn't provide much variability. The draft door on mine is not lubricated well and this proves to be fortunate because it will hold the door in any position I want.

There is also a tab welded to the draft door that prevents it being closed all the way when the wood door is closed. I'm not certain of the reason behind this but I may remove it at some point. I wold like to allow just a tiny bit of air so the fire keeps going for long periods.

- Neither the main door nor the draft doors have gaskets. This leads to smoke stains on the face of the heater and heat loss during operation. I may add these gaskets myself if I can find something appropriate.

- The heat exchanger is stainless steel (very good!) but it is only several rows of pipes above the fire. That means that when a fire is burning only in the back of the box, more heat is lost up the chimney, and the front part of the heat exchanger receives much less heat. I would like to see some channeling so that the heat has to travel farther over every layer of pipes before it comes out the top. While this would slow the draft I'm certain it would greatly increase efficiency without adding much cost to the stove.

There are also a few options I'd like to see offered but I understand they don't exactly sell millions of these per year and it may be difficult to design in such options.

- Glass in the doors: I would also like to be able to watch the fire. I can see what the fire is doing without having to open the door, and it can be optically pleasant to st around a fire on an evening.

- External heating: An additional heat exchanger added to the fire box through which air could be blown. This clean warm air could be used to heat under a covered outdoor pool, a local area for cool evenings, or even with a rack to dry and warm swimming attire and towels.

- An additional hole or two on the top of the stove with an insulated plug and "burner plates", between 6" and 12" diameter. With the insulated plug in the stove functions normally. Using the burner plates could allow limited cooking and food to be kept warm in pots or under covers on the stove.

===> Summary

Overall the heater functions as promised, and is a great way to cheaply heat the pool.

It does require labor, it is a bit messy with the wood and smoke, and it does not switch on or off quickly.

I believe it provides a good cost/benefit ratio.

Comments/questions anyone?

[NullQwerty]

Thanks for the great post! Very informative!

Few questions...

1) Cost (if you don't mind saying)?

2) If you kept it running for 24 hours, about how much wood would be consumed?

3) If you kept it running for 24 hours, how often would you have to poke/feed it?

4) Is there a constant fire odor in the pool area?

5) How bad is the smoke?

I know you said that it's hard to make those statements because it's wood dependent, but if you had to guess for normal wood that you'd get delivered for a fireplace for example.

Thanks again!

[Pool-newb]

Glad I could help and thanks for pointing out some stuff I should have included!

1) Cost (if you don't mind saying)?

Total cost was $2,475 including shipping, 2 "Pete ports" (these are plugs where you can insert a meat thermometer to check incoming and outgoing temperature) and one thermometer. They had a special on shipping though.

2) If you kept it running for 24 hours, about how much wood would be consumed?

This really depends on the type and size of wood. I have several types out there (i don't know which; gum and white oak are among them), all hardwoods, but I notice that some burn more slowly and some faster. Also the small old stuff that I split last fall goes very quickly and burns really hot whereas the same wood in huge chunks burns much more slowly and cooler. In the 3 or 4 days I had it burning I used up a section of one stack that was about 4 ft long by 5 ft high by about 18" long, plus several massive blocks.

If you are thinking about one of these, I would recommend you have a good steady source of cheap to free wood. If you have to purchase the firewood it may not be much cheaper than gas. Hard to calculate though. There are lists of how many BTUs a cord of wood holds for a given type of wood. These may help figure if it's worth it.

3) If you kept it running for 24 hours, how often would you have to poke/feed it?

This is again dependent on the type of wood, but also how you stack it in the fire box and how fast you want the water warm. If you have some time (I made time), if you know how to build a good fire (I'm still learning), and have good, large pieces of wood (i have mixed wood sizes and types) you can load less often, save on wood but take longer to heat, or you can get a bonfire going and blaze through a cord fast getting the water temp up fast. (Of course the male in me says I have to poke it and tend to it alot. )

In my case it was every 1 to 3 hours for a hot fire, and overnight (>8hrs) for a slow burning, efficient fire. In the morning the pool temp tends to be even a bit lower than in the evening, but not nearly as much lower than if you had no fire at all, and there should be (was) a bed of coals that was enough to get things going again.

4) Is there a constant fire odor in the pool area?

I've only had odor problems when starting or adding wood. I'm still learning but I think the trick is to get the kindling fire really hot before adding a small amount of real wood, and get the regular fire really hot before adding any large pieces. So far I've used the air mattress air pump only once but I will probably use it again in the future. That's a good way to get the fire hot fast so more wood can be added. A shop vac or compressor will probably also work well for this but with all of them you have to be careful about blowing ashes all over.

On the whole, usually though, odor and smoke are not problems.

5) How bad is the smoke?

Same as above, the smoke and smell get worse with the fire not getting enough air, or poor wood on the fire or other similar faults with the fire itself. You can order additional chimney sections to get the smell away from the local area, but if the weather is wrong - i.e. no breeze, and the fire gets ugly, you can get neighbors upset. I've asked all my neighbors several times to please tell me if they are having problems and so far, only my direct next door neighbors have smelled it, and one even likes the smell of a wood fire.

One other thing I wanted to make clear; this is a hands-on device. My pool is currently one of my hobbies, and I enjoy working on it nearly as much as swimming in it. Adding wood every few hours, or fiddling around with lighting a fire doesn't bother me (I may never get a salt system, either). If you're looking for something you can throw money at and forget, this isn't it (money burns well but doesn't have many BTU's). If you're pool-geeky, if you want to save some money, if you appreciate using a renewable resource rather than a fossil fuel, this may be for you.

Please let me know if you think of anything else I could/should include. I found very few comments on the web when I was researching this and I wanted to get some information out there.

[NullQwerty]

This was great! Thanks! I've looked into these in the past, and as you said it's hard to get good information out there.

Unfortunately for me that amount of wood runs me about $150 delivered, so I'd probably be better off with electric or gas. If the unit itself was only $300 or $400 it would still be worth it just to get the pool warm during one-off occasions.

Also, kind of what you were referring to with the glass window...what would be nice if someone developed a fire pit that also heats your pool. During the summer time I have countless barn fires in my backyard, and all that heat/energy is just lost. Would be nice if it could also be heating my pool at the same time.

Thanks again!

[Pool-newb]

According to their website they got started because the originator wanted heat and found that installing a gas heater was too expensive. It wasn't just the gas heater cost itself, but also the cost of running the gas line, running the electric and getting it all installed and the approved.

For me it was sort of a combination of "what to do with all this wood" and "I want a warm pool" and "$200 / month for a non renewable resource is too much".

My first idea was to make one and If I had the shop, tools knowledge and supplies available to me, I probably would have made it. A lot of ideas circulated in my mind, mostly revolving around a 50 gallon drum on legs sideways, and a copper heat exchanger. I have even seen plans and photos on the web of home built items, but I just didn't have the resources - including time, and I also didn't want to mess with copper - too reactive to pool chems, and too low a melting point.

If I even knew of a steel working shop I may have had them make me one to order. I'm not certain how much cheaper it would have been if at all, though I'm certain I would have designed it differently with a much close eye on efficiency.

With the glass window I meant that the current door is made of solid steel, and I would have liked to see it made of fireproof or fireplace glass. That kind of glass will get smoked and dirty when the fire is not burning well, but get the fire hot and it mostly cleans up well. Makes a good way to check the condition of the fire and the temperature.

If you're having barn fires, what is the fuel source - are you burning down barns :-/?

Sounds like you might want to take the time to build something yourself. $150 for that much wood doesn't sound cheap. I've never been able to tell exactly how big a cord is, but my best estimates is that I've burned about a quarter to a half of a cord so far, maybe a bit more. Most of the pieces were fairly short and small because I had the tree removers cut them expecting to use them in my extra small fireplace.

Another possibility is to get their stove and make some modifications like adding a flue damper and installing baffles that redirect the heat over all of the heat exchanger before directing out the stack.

I know I'm enjoying the 85 deg water (was out there just before midnight with my wife swimming. Cold outside, warm in the water).

[Pool-newb]

Live and learn

There has been a slight setback with my wood fired pool heater.

Here in Georgia at this time of year we often get thunderstorms in the afternoons and today was no exception.

Because the pool had cooled down to about 80°F I had fired up the heater earlier in the day. Now my intention has been to keep the stove covered with a tarp when It's not burning so as to prevent as much rust as possible. (One of the required maintenance items is to apply some bar-b-que flat black spray paint when minor surface rust appears.)

Well when the rain started today I checked the weather maps and it looked like it would be a 15 minute squall - and it pretty much was. I had a very nice fire going and left the draft open to keep things hot so it would keep as dry as possible in the brief rain.

Long story even longer, the rain wasn't a problem but the power failure that accompanied it was. To make matters worse, it didn't dawn on me immediately that I needed to cool the fire quickly so by the time it did, the water that was stopped in the plumbing got hot. Really hot.

Schedule 40 piping is ok at low pressures up to 140°F but when the power went and the water stopped moving, it must have gone well above that. I didn't get any explosive leaks but a large portion of the piping just sort of "withered". Sagged, melted, stretched, whatever you want to call it.

The actual water path is still more or less intact. Several minor leaks have developed around some of the joints but I can still pump and filter the water - I could even run the heater again but I know the plumbing needs replacing so I'll be out there next week sometime replacing a bunch of PVC stuff.

When I restarted the pump to check everything, the stove seemed fine - even under as much pressure as I could give it so I'm pretty certain that the heater wasn't damaged. Just the PVC piping leading away from the heater.

Not very expensive, fairly time consuming and certainly irritating but it hasn't reduced my appreciation of this heater - or at least the concept of using wood to warm the pool.

And you can bet that the next power outage will remind me of something very quickly.

p.s. I wonder what an emergency generator will cost ...

[NullQwerty]

Wow...Sorry to hear that. At least it wasn't underground piping though...Then it could have been a problem.

As you said, emergency generator should do the trick it sounds like though. You just need one that pops on automatically in case you're not home at the time.

Good luck!

[txpoolguy]

You should post some pics of the installation if you can. I've only seen 1 wood-fired pool heater in 25+ years, and you've been remarkably detailed and honest about the whole job - pros and cons. I always thought it was an interesting concept, but as you describe it as "hands on", I'm sure you won't have too many neighbors trying it out...

[Pool-newb]

I'm posting these under the caveat that the place is a mess and it is all still a work in progress. I took the photos during the first fire and the smoke you see is not normal. I had just stacked in some wood and I hadn't yet learned the trick of using an air mattress pump to heat the fire before putting in fresh wood.

I have also found out that there is a type of piping called "CPVC" that is very similar to the usual PVC but handles higher pressures/temps (180°F @ 100 psi) and I will probably move to that - and maybe add a temperature release valve.

Still learning.

Wow - I bet I get questions on these - for example,

- The wooden fence so close to the fire? No problem, the fire box is well insulated.

- The ugly brown box to the left of the pump? Previous owners stupidity rusted that heater out.

- Failed parts? I haven't photographed anything yet but three major items have failed; The short piece from filter to bypass T, the long pipe from stove to bypass valve, and one 45° elbow at the top of the return line. There may be other failed items, I'll know more when I get them apart. Either way I'll have to replace a bunch more than that.

- Spark arrestor on top of chimney? No - but planning on it. Hasn't been a problem yet ... but I need to replace that fence anyway ...

- Base for the heater? I intend to clean that up and make sure it doesn't float away during the Georgia rains. Should probably be a poured concrete slab.

- More?

======

=====

[Pool-newb]

Replaced all the damaged plumbing today and the fire is burning now. Dropped to about 75°F before I got it all done so I'll have to let it burn for a while before I get my required 83° again.

I also discovered on more inefficiency today. The lower sides of the heater also get very hot and that means lots of heat loss. I had some metal pieces sitting near it and burned my fingers when I tried to move the pieces. ... But lets make lemonade; I think I'm going to glue or use magnetic mounts for towel racks. Hot towels after a swim? Gotta love it.

[Pool-newb]

Great swim this evening in 30.0°C / 86°F water.

At ambient air temperatures between 68° - 72°F, and using a cheap solar cover on a 12x24 ca 8,500 gallon rectangular pool, from starting the fire at 5:10 PM yesterday to 5:24 pm today (24 hours) I was able to raise the temp from 77.4°F to 85.3°F (25.2°C to 29.6°C)

I added wood 11 or 12 times which averages out to about every 2 hours, but I went longer periods (over night) without adding, and added more often at other times. Again, this really depends on the type of wood, how dry it is, and how fast you want the pool warm. I also tended it more often, sometimes just checking, sometimes poking, so this is probably near the maximum performance I can expect with my wood supply and without using exclusively the stuff that burns fast and hot.

Heating history:

date time Temp °F/°C

05 May 17:10 77.4 25.2°C

05 May 18:09 77.5 25.3°C

05 May 18:56 78.1 25.6°C

05 May 19:19 78.3 25.7°C

05 May 19:26 78.4 25.8°C

05 May 19:41 78.6 25.9°C

05 May 19:59 78.8 26.0°C

05 May 20:13 79.2 26.2°C

05 May 20:53 79.5 26.4°C

05 May 21:37 79.9 26.6°C

05 May 21:55 80.1 26.7°C

05 May 22:33 80.1 26.7°C

05 May 23:11 80.8 27.1°C

06 May 00:22 81.1 27.3°C

06 May 08:50 81.5 27.5°C

06 May 09:22 81.7 27.6°C

06 May 09:37 81.9 27.7°C

06 May 09:52 82.0 27.8°C

06 May 10:23 82.2 27.9°C

06 May 11:15 82.6 28.1°C

06 May 12:03 83.1 28.4°C

06 May 13:24 83.7 28.7°C

06 May 14:19 84.4 29.1°C

06 May 14:49 84.6 29.2°C

06 May 15:44 84.7 29.3°C

06 May 17:24 85.3 29.6°C

[Pool-newb]

Just wanted to add an update on this.

I still like the heater despite the fact that I think the honeymoon is ending. We swam today in 90°+ water and I really enjoy water that warm.

I still don't mind - even enjoy - splitting the wood, and I still don't mind tending the fire or cleaning out the ashes after a few days burn.

I do wish it had better smoke control. While that may be in large part due to the wood I have and possibly because that wood is not fully cured yet, I just feel uncomfortable having the smoke float around the neighborhood while I'm starting up or putting in large amounts of wood. Nothing horrible or even irritating, just a bit distracting.

Another thing that keeps staying in my face is the inefficiency of the setup. I can get really great temperatures out of it, and the water does warm up fairly fast but every time I stand near it I feel how much heat is being wasted, and I see how hot the chimney gets, and I start thinking about ways to supercharge it;

- add insulation on the sides,

- add baffles on the inside so the chimney gasses have to travel farther and over more heat exchanger before they escape out the top,

- add a blower and some air intake piping so the air input can be accelerated on startup and better controlled for restriction

- add a stovepipe damper so I can reduce the amount of chimney flow to a) slow down the fire and keep more heat around the heat exchanger for longer

- Insulate the door or make it a glass door

- Enlarge and lengthen the heat exchanger so it not only covers the top but also the sides and back.

The last thing to mention is the lack of automatic control. There is no way to quickly disconnect the PVC if the pump should fail for some reason. I already had to replace a bunch of PVC when the power failed and I didn't remember to put out the fire soon enough, and since then I had another incident where the water was hotter than I expected and it made one section of PVC sag a bit. No leaks or failures but still irritating. Even forgetting to switch the pump to constant on when the fire is burning is an easy mistake to make that will cause big problems.

I've given it a lot of thought and there is no easy or cheap solution to the dilemma. Anything that covers all possibilities - pump failure, power outage, leaking, would require a lot of engineering (some combination of battery back-ups, electric 2" valves, breakaway piping, fire extinguishers, etc.) This is a point where any other kind of heat except possibly solar wins by a huge margin.

Still, having said all that it's great to swim in May in such a warm pool which gets so much shade but to still pay nothing for the heat. I can still recommend it in many situations.

More later

[njpoolbuyer]

Just wanted to pass along a little information. I live on Long Island NY. Recently, one of the towns passed an ordinance prohibiting the use of wood-fired heaters for purposes of heating a pool. Reason was primarily due to air quality issues. Experience has borne out that once one town on Long Island moves, others follow.

[Pool-newb]

Thanks for the info, that's good to know and it reemphasizes my frustration at the inefficiency and design of this particular mdel.

Do you know why the legislation was enacted? Were there problems? Maybe a councilman's neighbor has rigged up something home made and that got the ball rolling?

And which city was this? I'd like to do some further research.

[njpoolbuyer]

Pool-Newb - attached is the article.

Newsday.com

Huntington approves ban on outdoor wood-burning devices

BY DEBORAH S. MORRIS

deborah.morris@newsday.com

8:13 PM EDT, May 25, 2009

The Huntington Town board has unanimously approved a measure to ban outdoor wood-burning devices beginning in January.

The banned devices, which resemble outdoor sheds with a tall smoke stack affixed at the top, burn wood to heat water that is pumped through underground pipes to a home's plumbing and heating systems and sometimes even pools.

The measure was passed during the town board meeting of May 19.

"These devices are incredibly carcinogenic," said board member Susan Berland, sponsor of the legislation. "The emissions that these things let off are awful and have been banned in other states."

The measure says the only time the units, sometimes called outdoor wood-boiling furnaces or outdoor wood boilers, would be allowable would be during an emergency or natural disaster.

Burt Tobin, a distributor of the devices through his company Catskill Boiler Company in upstate Greenville, said the ban makes sense in Huntington and other densely populated areas.

"Unless someone is sitting out on 5 acres of land somewhere, a [outdoor] wood boiler has no place," said Tobin, who lived in Brooklyn and attended Hofstra. But he said there should not be an overall ban because in rural communities, including the East End of Long Island, the units are beneficial and economical.

In 2006 Berland sponsored legislation that defined what could - and could not - be burned in all wood-burning devices, and limited the use of outdoor wood-burning devices.

"People who use them often throw everything into these things to burn," Berland said, "from soup to nuts, things that you are not supposed to burn," such as painted wood and even solid fuel.

The ban only applies to outdoor wood-burning devices that are used to heat indoor spaces, swimming pools or hot tubs.

"You can still have wood-burning stoves in your home, you can still have fire pits outside, barbecues, it doesn't ban any of that," Berland said. "Just this one type of device which is really bad for the environment."

Berland said currently no one in the town has a permit to have such a device. Anyone found to have one will receive a first-time penalty of between $250 and $1,000. Second or subsequent offenders will receive a penalty between $1,000 and $2,500.

[bobd]

Just wanted to add an update on this.

I still like the heater despite the fact that I think the honeymoon is ending. We swam today in 90°+ water and I really enjoy water that warm.

I still don't mind - even enjoy - splitting the wood, and I still don't mind tending the fire or cleaning out the ashes after a few days burn.

I do wish it had better smoke control. While that may be in large part due to the wood I have and possibly because that wood is not fully cured yet, I just feel uncomfortable having the smoke float around the neighborhood while I'm starting up or putting in large amounts of wood. Nothing horrible or even irritating, just a bit distracting.

Another thing that keeps staying in my face is the inefficiency of the setup. I can get really great temperatures out of it, and the water does warm up fairly fast but every time I stand near it I feel how much heat is being wasted, and I see how hot the chimney gets, and I start thinking about ways to supercharge it;

- add insulation on the sides,

- add baffles on the inside so the chimney gasses have to travel farther and over more heat exchanger before they escape out the top,

- add a blower and some air intake piping so the air input can be accelerated on startup and better controlled for restriction

- add a stovepipe damper so I can reduce the amount of chimney flow to a) slow down the fire and keep more heat around the heat exchanger for longer

- Insulate the door or make it a glass door

- Enlarge and lengthen the heat exchanger so it not only covers the top but also the sides and back.

The last thing to mention is the lack of automatic control. There is no way to quickly disconnect the PVC if the pump should fail for some reason. I already had to replace a bunch of PVC when the power failed and I didn't remember to put out the fire soon enough, and since then I had another incident where the water was hotter than I expected and it made one section of PVC sag a bit. No leaks or failures but still irritating. Even forgetting to switch the pump to constant on when the fire is burning is an easy mistake to make that will cause big problems.

I've given it a lot of thought and there is no easy or cheap solution to the dilemma. Anything that covers all possibilities - pump failure, power outage, leaking, would require a lot of engineering (some combination of battery back-ups, electric 2" valves, breakaway piping, fire extinguishers, etc.) This is a point where any other kind of heat except possibly solar wins by a huge margin.

Still, having said all that it's great to swim in May in such a warm pool which gets so much shade but to still pay nothing for the heat. I can still recommend it in many situations.

More later

I just installed basically the same pool heater a few days ago which I bought used (two years old) off a local pool installer. I was lucky to find your post, it's been very helpful since I never got any information or literature when I bought the heater. I fired it up just yesterday and so far so good, but I am experimenting on how to get the most efficient burn. Have you tried different position on the lower damper door to get more heat? Also, wondering if your burning seasoned wood or green? Any insight would be appreciated.

[Pool-newb]

Pool-Newb - attached is the article.

Newsday.com

Huntington approves ban on outdoor wood-burning devices

BY DEBORAH S. MORRIS

Thanks njpoolbuyer. When I hear "...those things are incredibly carcinogenic..." I have to ask what evidence there is to support that.

I also think it's too bad they were banned but I also completely understand why. I also understand what they were referring to about the small huts. I've seen those on the web and since they are heating the entire house in deep winter I imagine they can be much more problematic.

I think a better path to have taken would be to require some sort of EPA testing or emissions requirement instead of forbidding them outright. I seem to recall that Washington State came up with some very tough laws for normal wood-burning stoves and that got the manufacturers to start engineering and then advertising how clean burning the stoves can be.

Still, if someone has s a roaring fire behind a gaping hole, I can imagine the garbage burning that happens.

Too bad, really.

I just installed basically the same pool heater a few days ago which I bought used (two years old) off a local pool installer. I was lucky to find your post, it's been very helpful since I never got any information or literature when I bought the heater. I fired it up just yesterday and so far so good, but I am experimenting on how to get the most efficient burn. Have you tried different position on the lower damper door to get more heat? Also, wondering if your burning seasoned wood or green? Any insight would be appreciated.

Well, congratulations, I hope. Can you tell me if the heat exchanger is stainless steel or copper? I think they were making them from copper first but they had too many problems and have now switched to stainless steel. I also have not yet been able to find the goo they used to seal the top (and expect me to use to seal the chimney). I found some fireproof mortar at HD and Lowes, but that stuff turns crumbly and brittle.

By now you're probably swimming in 90° water if you haven't had any of the problems I've had. I can only say make sure you have as much water pumping through it as possible when there is any heat in the fire box. If the pump stops (mine was power outage) use a garden hose to put it out as quickly as possible - without flooding the fire box of course. It worked well for me I just didn't think to do it fast enough and I had problems.

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It depends on what you mean by "seasoned". I had 7 or 8 trees removed and the wood left in the yard. They were different types of hardwoods and some were taken down last fall, and the last two were done this spring (April). I am still using the older stuff but I notice a huge difference in the way the different types of trees burn. One type is very light colored - nearly white, and burns well and hot. The other pile is a bit darker and has some wood that is very splintery and burns well though not quite as well as the white stuff, and the third type burns very slowly and cool.

I am constantly adjusting the lower damper and it does work but I still feel they could have done a much better job of air flow control. If I put only white stuff I have to close it almost to zero to keep the chimney temp from overheating. If I'm using the third type alone I need to keep it wide open and even then it just barely coasts along at the bottom range of the chimney thermometer. I usually mix the two or three types of wood, and I often split it as I go so by managing the log size and wood type I can fine tune it for what I want to do.

A typical burn lasts two or three days and starts with mostly the white and splintery stuff. Once it's going well I'll mostly add the third stuff with a few small white pieces to keep up the temp. To keep it going overnight I stuff it as full as I can with a mix of splintery and slow stuff, then close the draft to almost nothing, then let it slumber till I get up the next morning. If I can't tend it for a while (like if we leave the house) then to revive it I grab some more of the white stuff.

Let us know how it's going with you on this.

[Anvil]

Finding such a thing on the web was not easy. There are only a few available and I was only able to find one that sits outside the water There are "hot tub" wood-fired water heaters that sit completely in the water except for the smoke stack and wood feeding box but I didn't want to sacrifice any of my pool for this as it's already too small, and I didn't want the mess around the pool either.

So I called the guys at ExtendaSwim - the only other manufacturer I could find - and ordered one.

The individual taking my call suggested I order the middle sized heater even though the smallest heater was more appropriate for my pool. Apparently they were doing a redesign of the smallest one and the delivery time would have been fairly long. I followed his advice but more because the wood I have is partially in large pieces, and also because I wanted to be able to heat quickly and shut it down. I live in a typical subdivision of smallish lots and I was (and still am) concerned about the effects of smoke in the neighborhood.

Very informative. Im from a farming background with access to alot of free wood that i just need to cut. I would like to know how your heater has preformed now after a longer time, what other issues you have had with it, weather you have changed anything like your posts talked about. I have done some more looking around and have come across this company http://www.woodstovepools.com/contact-us.html was it avalible when you looked for your heater? with reading this post and the info on that site it seems to have covered the changes that you wish you could have done on yours.....

any info you could give would be greatly appreciated

[Groo]

The old-school outdoor boilers were very smoky and inefficient because they burned at such a low temperature. modern designs use high temperatures, and a secondary burn to get very high efficiencies. As a pool stove would have no need to sit and smolder all day to provide a constant level of heat, it would be much easier to make a high efficiency type heater. We currently heat our house with a wood furnace, andI've been researching outdoor boilers for the next place.

seams to me that a well setup wood fired pool heater could move the water through convection and not even require a pump if set up below the water level

[Anvil]

my parents, and all my life for that matter heat their home with an air tight wood stove. so i know that the effeciency is there to heat a large area with a small amount of wood. much the way there has been a progress in the design of outdoor wood heaters for homes have become much more effecient on the amount of wood used. with the site that i have just found it seems to me that it is a much more insulated and air tight stove than the other in this post witch would result in more effeciency. the way it looks is that this new one i have found is more of the high effecieny type, but in general i would say that a wood heater would be used to push the temp up to the max then allow the pool to cool as it would so there would be no need to let the stove smolder for any length of time... just my thoughts

[Pool-newb]

Thanks for the bump and sorry it's taken so long. This is my third attempt due to various PC problems - gotta love modern technology.

My initial conclusions remain pretty much the same, here are some random thoughts after a year of using this heater.

We made the decision in late February or early march to go ahead with the liner replacement so I stopped heating at that point. The liner was done in April and except for a brief initial period, the weather heated the water enough so that burning wood was not necessary.

The heater available at woodstovepools.com was not available when I purchased mine and it may be better in several aspects:

- The door is insulated and from the description it sounds like the rest is insulated better than mine. This will of course help efficiency.

- The exterior is stainless steel and besides making it look nicer (matter of taste) that will also eliminate the routine sanding and spraying with black spray paint to remove surface rust on mine. Caveat; while stainless steel is normally rust resistant, it can still rust and if it does I'm not sure how much effort would be involved in removing the rust.

- Also from the description it looks like they did a much better job designing the heatbox and burn area. The air intakes appear more finely tunable and they talk about baffles to reduce unburned gases. However, they also claim that one bush cord will heat the entire season and that is a blanket statement that simply cannot be made without considering other variables like wood type, desired water temperature, weather, pool cover, etc.

But their website doesn't state how much it costs and that would be an important factor deciding whether to buy on or the other.

They also haven't solved the problem of what to do if the water stops. Groo, I like your idea of having the heater below water line but with the size of these heaters I think that would be impractical. Still, I wonder if the heat exchanger could be installed vertically or at an angle to allow at least some convection powered flow - not for normal use but enough to protect things when the water stops. Maybe even a simple hand pump built in to keep the water flowing while the fire cools off. 

Either way I think any solution to this would require expensive engineering which given the low numbers of these heaters will probably not happen.

I found and bought at a local chain hardware store (Lowe's and Home Depot did not have them, Ace and Gilroy's did) an 8" cast iron flu damper and a 2 pieces of 8" stovepipe. While the assembly was not as straightforward as I hoped (problems caused by the male/female matching), it was an easy and not too expensive way to make it look a bit better and provide better draft & draft control while also moving the smoke up a few feet higher. Was not a very impressive change.

Most important for maintaining a pool at a warm temperature is keeping it covered. I was in the pool in February with it over 80° but I was under an oversized solar blanket and my main goal at the time was to find some way to support the cover high enough so it could remain on the pool while we swam. I was unsuccessful at the time but I'm not done tinkering with that yet. The point is that an outdoor uncovered pool in the Atlanta area will cool off so quickly in the winter that it makes no sense to bur the wood unless someone is spending several hours daily in the pool. I will continue looking for some kind of cover solution but most of the commercial products (removable in summer, swimmable and insulated in winter) I've seen so far are just too expensive.

The best way to look at this kind of heater is really in the name; "Extenda-A-Swim". Without additional protection it will simply extend the swimming season. 

I still believe that for those communities that have outlawed these there must be a better way to prevent local air pollution. Mine would probably deserve a restriction too but I am as careful as possible. I never burn anything but wood (paper and cardboard to get the fire started) and I always ask all of my nearest neighbors if they are having any problems with the smell or smoke. So far, not even the elderly person on constant oxygen whose kitchen is about 12 ft from the heater has had any problems. I also now have enough experience (and my wood pile is a bit more seasoned) to keep the worst of the smoke down and it usually burns fairly cleanly - albeit very inefficiently. 

One topic that is rarely broached in the emissions discussions is the source of energy. Oil is solar energy that was deposited on the planet a long time ago and consuming fossil fuels converts that stored energy into heat, warming our current environment. Solar thermal, photo voltaic, and wind are all solar energy sources that were deposited on the planet recently and are energy balance neutral. Wood is a form of solar energy that was deposited on the planet generally within the last hundred years and it is renewable. Not as good as direct solar but certainly much better than fossil fuels. 

While this new heater model may change things and I don't have any experience with it to be certain, my primary conclusions remain the same. The appropriate installation for a wood-burning pool heater is one in which the owner/user:

- doesn't mind the manual labor involved with burning wood

- doesn't mind spending time to feed and care for the fire

- has a cheap or free source of wood

- has a large enough area around the heater or is conscientious enough to ensure that no neighbors are bothered by the emissions

- is willing to keep a thermal cover on the pool except when swimming

- wants to extend the season by a month or two on either side