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Sanitization (And A Few Other Questions) For A 3K Gallon (Teeny) Pool


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#1 hlwimmer

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Posted 05 July 2012 - 05:39 PM

Hello: We're currently building (DIY as best we can) a super small 8X12X4 vinyl lined pool. As planned, it will have one suction (skimmer only) and two returns and will be powered by a Hayward Powerflow2 (1/2HP) pump fed to a 250SF Hayward cartridge filter. It will be plumbed with 1.5in lines and sit 2/3s of the way in ground with a low deck surrounding it. I'm planning the plumbing for potential (future) roof-top solar and electric heat. (First question: Thoughts on the overall equipment set-up?

We're now thinking of the type of sanitization we need: tri-chlor, bromine, salt-cell, ionizer, etc... the main contenders are trichlor (potentially with a Nature2 add-on) via a small inline feeder or salt-cell. Perhaps this is a question for the Sanitization board, but it involves equipment, so here goes...

The problem with all of these is that they seem to be designed for (or optimized for) very large pools (15-40K gallons) and I'm at a loss as to what would be appropriate for our new, very small pool.

The goal is to have something low-maintenance and easy. Since it's our first pool, making it easy as possible trumps saving costs. We're not opposed to any chemicals or processes, but would rather not buy into snake-oil or gizmos that will be unrepairable or useless in 3 years.

My thoughts...

Chlorine: Since the pool is small, it shouldn't take a ton of chemicals anyway. I was thinking a 4.2lb Hayward inline feeder with trichlor tabs would be straightforward. I /do/ however, want to protect my (black) vinyl liner from damage or bleaching, so i'd love to use as little as possible

Nature2: Of the "miracle" cures, this one seems to have stuck around the longest and claims to allows me to use less chlorine. True? the CF or Express models seems like they could work for my setup, but unsure of the efficacy.

Salt-chlorination: Undoubtedly, on larger pools, the payback is more but the same $800 system seems sized to treat a 15-40K pool... 3X to 8X my need. granted if the salt cell would last 3X to 8X longer on my teeny pool, it might prove worth it, but i'm unsure of that. The draw here is ease more than chemical-cost-savings, but is it really "easier" and less time consuming?

Any wisdom would be most appreciated... thanks.
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#2 PoolGuyNJ

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Posted 06 July 2012 - 03:19 AM

Hayward in line chlorinators restrict the flow to 3/4" and create an unwanted head loss. A Pentair Rainbow 320 doesn't do this. Trichlor gets the nod. Bromine is only good for covered portable spas. Ionizers don't work.

I would urge you put a pair of drain pots in for bottom drains and valve it with the skimmer.

Use an in-ground pump, not an above ground.

Nothing reduces the levels needed in a pool. You can only augment it. IMHO, the N2 is a waste. Chlorine gets whatever the N2 gets only faster already.

No real need for a cell. Is it easier? Not enough so here. Just watch the CYA level. Any replacement water used for dilution won't be that much.

The sun's UV will be the big fade cause, not chlorine used properly.

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#3 hlwimmer

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Posted 06 July 2012 - 06:09 AM

I would urge you put a pair of drain pots in for bottom drains and valve it with the skimmer.

Use an in-ground pump, not an above ground.


Excellent -- thanks.

-- re: Drain pots... We've already been though code-review with the current design, so, this addition is unlikely and a bit more difficult to add in the vinyl-lined sand-bottom pool. Essentially, it's a swim-spa without the current -- pretty low-fi, but most of thee units use a spa-pack and skimfilter set-up. I was worried about the single point of suction, but curiously enough, I went to a friend's house with a pool 5X the size and he has only one point of suction and one return and it has been working amazingly well. It was encouraging to see/hear his results.

-- re: Pump... We presently have a Hayward PowerFlow2 (1/2HP), which is a self-priming pump. This would work, no? If not, why?
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#4 waterbear

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Posted 06 July 2012 - 06:22 AM

I second what PoolGuyNJ said. Stay away from the hayward and go with the Pentair chlorinator. With trichlor you will need to watch your stabilzier levels and do partial drains and refills on a regular basis.
I would not go with a cartridge filter if you are going to use trichlor, this is a sure recipe for fast overstabilization. Consider a sand filter instead. The backwashing will help keep the stabilizer levels down.
N2 adds copper to the water so it is really just a very expensive copper algaecide and not needed at all. It does not allow you to run lower FC levels, particularly in a pool as small as yours where the bather to water ratio is almost as high as in a hot tub.

As far as whether the SWCG would be cost effective, much depends on where you are located. If you are in an are where you have a short swim season and winterize the pool then the trichlor feeder makes sense. If you are in an area with an extended or year 'round swim season the your small pool WILL overstabilize on trichlor and using a SWCG makes sense. IF you go the SECG route then the cartridge filter is the best way to go, particularly in a pool as small as yours. As an alternative, you could manually chlorinate with liquid chlorine or bleach instead of using trichlor but that does mean daily pool maintenance (even though we are only talking about 5 minutes a day or less).
NO matter which way you go get a GOOD test kit. The best one would be a Taylor K-2006 (not the less expensive K-2005). It is the best value for the money (at both US and the more expensive Canadian pride) and is the best investment you can make into the maintenance of your pool.

Good luck on your new pool!
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#5 hlwimmer

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Posted 06 July 2012 - 09:12 AM

thanks, waterbear: i've been reading a few of your re:s in the chemistry section -- thanks for the input.

re: filter... given the location (a small utility closet) and lack of immediate access to a wastewater drain, the cart-filter made the most sense. while i can remove the filter and wash elsewhere, CA regs require any pool drainage be into a sewer (not stormwater) drain -- specifically going to the main cleanout (not through house piping). overall size/space is also a factor as the closet isn't huge and the cart-filters seem to be smaller in physical size.

re: maintenance... while i'm no slacker (re-built our MCM house with my bare hands [ http://www.redneckmodern.com -- pool plans there, too]), i'm apt to fall into project rabbit holes and emerge days later, so //required daily// maintenance will be tough. this was one of the considerations for the SWCG.

re: pentair SWCGs ... i'm reading that they should be installed on a 2in line. my lines -- as planned -- will be 1.5in... a problem? the "above ground" pool version (IC15) looks tempting since it has a lower output (only 3X what i need as opposed to 8X) and a simpler installation.

so... longevity of the SWCG cell. on a smaller pool would one expect the cell to last longer or is it a fixed lifespan no matter the volume?

other notes:
... the pool is a steel-wall, vinyl lined pool. any concerns about wall corrosion with a SWCG or is the liner protection enough? thoughs on overall reduced lifespan of the pool walls with a SWCG?
... per reading the other threads on mineral sanitization, that's completely out. no N2...
... i already have the taylor k-2006 in my amazon shopping cart.
... any news on the autopilot SWCGs? ... the manifold design is ingenious (i guess the vertical, space-saving design could be incorporated in other installs)
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#6 PoolGuyNJ

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Posted 07 July 2012 - 04:03 AM

All pools, except for the blow up ringed Intex pools should be bonded. If corrosion is present, whether from a cell or other stray current sources, a zinc anode can be added to the water flow path to absorb them, stopping corrosion essentially in its path as long as it's bonded.

The Powerflo II is OK but it is a PITA to change motors and seal sets. The Whisper Flow (Pentair) or Super Pump (Hayward), while somewhat more money, will serve you better going forward. They are much easier to work on.

Adding drain pots using hard pipe and setting them in vermiculite and Portland cement (too keep the area smooth when changing liners) is easy in the construction phase. They will help, especially if the water is a little too low to run the skimmer. This can happen when vacuuming to waste. The will also help some keeping the bottom clean. If you winterize, they only need to be air locked with a valve.

Adding a pint of bleach would be the daily if a tab feeder or a salt cell isn't used. If that took more than a couple minutes, start to finish, I would be surprised.

Salt cells know two things, either they are on or they are off. Most cells are designed to have about 10,000 hours of on time however, the friction of the water going through them varies with the water velocity through them. This friction will wear away the coating on the cell blades the faster the water is moving. While a 0.5 HP pump won't push the velocity to extremes, using 2" pipe before the cell and to feed the returns will further slow the water. The returns can be stubbed with 1.5" pipe that are fed via the 2". 2" Pipe can handle twice the flow of a 1.5" pipe at a given velocity.

California is another land when it comes to filters. Cartridges are often used here for the exact reason the OP mentioned. Drought areas are also using them to reduce water usage. The reason CYA levels go up is simply due to the lack of backwashing creating a situation where dilution from refilling doesn't happen.

Whenever cartridge filters are used, use the biggest that your space will allow. I also highly recommend a 3-way valve be plumbed on the pump's discharge to allow you to both lower the pool, say, after a rain storm, and to allow vacuuming to waste after an algae bloom or period when there is a significant amount of debris. This helps minimize cartridge cleanings and makes emptying much easier..

If you are burying an on ground pool, make sure it is designed for it or it will rot out on you.

On ground pools often have thinner liners, shortening their life expectancy.

Changing liners on a buried ABG that isn't designed to be buried can result in the walls collapsing when the pool is emptied.

Using a beaded liner mean you won't have to remove the top rail like an overlap liner would.

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#7 hlwimmer

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Posted 08 July 2012 - 12:59 PM

excellent, thanks, scott.

... yes, the pool and equipment will be bonded. the pool is permitted and bonding is high on the inspector's list. even the water with the curved bit of metal that you put in the skimmer. fortunately, he doesn't want/need to see the wooden deck bonded, but any metal (ladder, etc.) will be bonded.

... good to know the PF2 will work. if something goes south, i'll likely just replace the motor -- it was relatively inexpensive.

... presently, the pool is permitted/designed without a drain. if i can get it inspected and passed before the liner goes in, i might contemplate a bottom drain or a low drain on an adjacent wall to the skimmer.

... presently, i'm thinking a salt-cell would be nice. the hayward aquarite and aquarite-pro seem to be able to be run on 1.5in piping which is good. good to know, too, that it's an "hours of use" thing with the salt cell. hopefully with my shorter filter times, it will last even longer.

... definitely planning a 3-way valve (or simply a T with an outlet -- many neighbors have a spigot) for drainage after the filter for the rainy season.

... good point about cartridge size. the pool is small (2.5Kgal at most) and presently i have a 250SF filter. i might look into a 400SF.

... the pool is made by kafko and designed to be buried. i'm also looking to my engineering friends (my wife is a structural engineer and coated rebar is her game) to see if there's a coating -- even autobody undercoating -- that can be sprayed to reduce corrosion in-ground. with a salt cell, i'm a bit worried about a liner leak and the salt corroding the galv. steel... maybe i'll epoxy paint the inside. i plan on using the thin foam on the walls and floor, too.... i'm pretty sure the pool has a beaded liner coping that will be added to the top of the panels.

thanks, again... hopefully the pool guys will return from vacation next week so i can finalize my order.
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#8 DaveH24

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Posted 08 July 2012 - 01:45 PM

What do you intend to use a small pool for, sounds very much like it should be a swim spa, If you're still designing have you considered a swim jet. This is the one thing I'd like to add to my 18'x11'x 4' pool. and I think it is cheaper and easier to do this as you build, rather than afterwards.


BTW I'm running this on the lines of a dichlor/beach spa.

#9 hlwimmer

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Posted 08 July 2012 - 02:47 PM

hi dave: yes, it's essentially a swim-spa without the current -- i'm not a swimmer, per se, but i love the water (lounging, etc). it started as an interest in endless-pools "waterwell" (which is a bit too expensive for what it is) and evolved into this small pool. at one point, we were even entertaining a HUGE (10ft diameter) cedar tub, but the yard can't accommodate the width and it was a bit pricey.

"BTW I'm running this on the lines of a dichlor/beach spa" ... i'm not following you here. could you rephrase?
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#10 waterbear

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Posted 09 July 2012 - 07:29 PM

dichlor/bleach is a variation of pool care known as BBB (bleach, borax, baking soda) started by Ben Powell at Poolsolutions and Poolfourm both excellent sites to learn basic pool care! I highly recommend both but I will warn you the info does not go along with what you will hear from builders, chemical companies, and pool stores!

Dichlor/bleach is basically BBB for hot tubs which have a much higher bather to water ratio than pools and are kept covered so there is less loss of chlorine from UV from the sun so the stabilizer level is kept much lower than in a pool. The initial CYA is added by using dichlor (a stabilized chlorine which adds 9 ppm stabilizer for every 10 ppm chlorine added. FWIW, trichlor adds 6 ppm CYA for every 10 ppm of chlorine added. Because of this there is more of a problem with persistent combined chlorine and more of a problem with pH control because of the increased aeration of the jets. However, since you are not installing jets and (hopefully) will not be covering the pool straight BBB would be more applicable. BBB is also (with a few modifications) excellent for Salt pools. As far as the actual units go, Autopilot is at the top of the list followed by the Hayward/Goldline and Watermaid units, IMHO. Pentair has has problem swit the untis in the past but supposedly have worked them out. Not a fan of Zodaic and Jandy (which is owned by Zodaic) .
The cell will last longer in a small pool than a big pool and, if you go with Hayward/Goldline the T-3 cell would be more than adequate for your pool. Ditto for the Autopilot units, the smallest cell is all you need.

One note about cart filters, They usually have an air relief valve on them that is opened after the filter is cleaned or if the pressure seems to be 'off' to release any air in the filter tank so it is filled with water. Normal practice is to open the valve until a strong stream of water shoots out so it might get messy in the utility closet if there is no where for the water to go (and this is not optional).

An explanation of BBB (which is really just good pool maintenance)--

Bleach is sodium hypoclorite at 6% and pool chlorine is sodium hypochlorite at either 6%, 10%, or 12.5% but is not available in all parts of the country, while plain laundry bleach is. Sodium hypochlorite is a form of chlorine that has fewest side effects (basically pH neutral, does not increase calcium, does not increaase stabilizer) and is inexpensive to use (the other form of chlorine without side effects is lithium hypochlorite but is is the most expensive form of chlorine you can buy!)

Baking soda is USP grade (pharmaceutical and food grade) sodium bicarbonate @ about $.50/lb (that's 50 cents). Total alkalinity increaser from the pool supply is industrial grade (not as pure) @ about $2.00/lb. Do the math. Oh yeah, the stuff for pools says it is sodium hydrogen carbonate, which is just another name for sodium bicarbonate.

Borax is used for 2 things. It is a pool/spa additve (illegal in California) sold by major pool chemical companies (as the pentahydrate form of sodium tetraborate, it has 5 water molecules attached to it) at a high price to act as an algaestat and pH buffer. 20 Mule Team borax (the decalhydrate form with 10 water molecules attached so you need slighly more by weight to get the same level of borate in the water) IS the same thing when the amount by weight is adjusted (or boric acid can be used also). When used this way borax needs to have muriatic acid added to keep the pH in line (which will bring us to the next use for borax in the nest paragraph.) The boric acid does not. It is an excellent additive for salt pools but since you cannot get the commercial products in California but can get borax in the laundry aisle at the grocery or Walmart... ;)

It's second use is as a pH increaser since borax raises pH but has minimal impact on total alkalinity. The normal pH increaser sold by pool supplies is sodium carbonate (sal soda, soda ash, washing soda) and can also be found in the laundry aisle as Arm and Hammer Super Washing Soda for much less money. HOWEVER, sodium carbonate also increases total alkalinity to a very big extent as it raises pH and usually causes the TA to go too high and need to be lowered after, The only pools that really need sodium carbonate are pool run exclusively on trichlor tabs, which are very acidic and deplete TA and cause pH to drop.
In all other pools Borax (used at twice the weight of needed amount of sodium carbonate) will give the same pH rise while not having any great effect on TA, which is usually what is needed.

Hope this clears up some questions before they are asked! ;)
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#11 hlwimmer

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Posted 11 July 2012 - 05:44 AM

wow. thanks, waterbear.

re: bbb/salt: there's certainly a lot to learn insofar as chemistry, but i geek out on that stuff, so it should be ok. i'm a very hands-on learner and once things are up and running it will be easier to visualize/conceptualize the balances... but the first step there will be to get it set up properly and your thumbs-up for the T3-aquarite is comforting. since the salt system needs to start with a balanced pool, my thinking is to hire-out for help for an initial set-up/balance and take it from there. i'll aim for the method which is the least time-intensive (or ability to be automated) more than one that shaves costs. i'm also thinking of "investing" in the aquarite-pro in the case that i do want to add automation in the future... the extra $100 there might be worth it to have that option.

re: cart-squirt: while the machines will indeed be in a closet, a little water is fine since it won't need to be diverted to waste. a full backwash would be impractical, tho.

re: swim-current: my wife wisely put the kibosh on the additional $3-6K swimspa jets... ;)

i've finally heard back from the kit-builder, so hopefully i can get the order in and have this erected in a few weeks.

the biggest "hmmm" right now is the idea to coat the back (or even the insides) of the galvanized shell to prevent as much rust as possible. the pool (kafko) is made to go into the ground, but if $200 in auto underbody coating gives me 10% longer shell life, it'd be worth it at this stage... thoughts?
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