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Hi fellow members,

I have been on a journey through the posts to decipher a proper maintenance routine for wood hot tubs. I have been through many tub makers manuals, and spoken with the maker of my tub. It was good fortune that I landed here on the forum! Thank you contributors for a good grasp on water chemistry and especially for the Dichlor/Bleach method. 

Here is what I have found. There is no good consensus on how to maintain wood tubs. Many have posted that their new tubs are being  turned to pulp by ozone/chlorine/Bromine etc. Dr. Spa on this forum recommends very low dose Dichlor method below 3 ppm FC coupled with ionizer, same with Roberts Hot Tub recommendations, yet is this enough to safely deal with Bather load. Other tub makers are proponents on ozonation and mps, but is there sufficient sanitation with this approach. Roberts Hot Tub told me I would only need 1/2 tsp of Dichlor 2-3x/week. Also Dr. Spa has warned against the use of ozone, Bromime, and mps as hazards to wood tub life expectancy.

The last 2 years I was using this very low ppm approach with Dichlor, until my wife got the rash and the tub tested positive for pseudomonas. There was poor smelling water. 

I have been very leery of super chlorinating the spa due to posts where users encounter wood fiber disintegration. 

I recently performed a modified decontamination using a fresh fill with Ahh Some, purged then drained. Then a fresh fill to rim balancing and adding higher levels of Dichlor in stages 10 ppm, next day 10 ppm, then over next few days bringing level up to 5ppm. Following morning I have grater than .5 ppm. Here is my question, because wood is organic will the CD always remain high? I have begun soaking once again and adding 3 ppm Dichlor after soaks, next day testing to .5 ppm FC. So far the wood seems in great shape with no visible degradation. I can see that I need to add higher levels after soaking to achieve 1 ppm FC prior to next soak. My concern is that these low amounts suggested by many of the wood tub suppliers will not manage bather load. I plan on another 10-20 ppm FC addition just prior to next refill.

I found several posts here where sanitizing methods where degrading the wood, or others had sustained rashes, others afraid to use bleach. There appears to be a lot of confusion.

Are there any long term cedar tub users who could help put together a safe maintenance routine for wood tubs. Perhaps even a decontamination guide. I for one would feel at ease knowing I was operating within reasonable guidelines and not putting bathers at risk. 

Nitro, I have been reading through your post on Chlorine Demand. My demand is over 75%. Is this to be expected with wood tubs? Will the Chlorine always go after the wood until the FC is close to zero.

Is there any guidance so we can keep our soakers safe and our tubs intact?

Could there be a go to category for wood tubs that could adapt/modify all of the good science and successes found on this forum towards the wooden spa family. 

Best regards,

Michael

 

500 gal Red Cedar Roberts Hot Tub

Pentair intelliflo pump, Mastertemp 125 heater, Clean and Clear filter. Sunshine pool ionizer, Multiwave controller

Bleach/Dichlor method, Proteam Gentle Spa

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  • 2 weeks later...

Would still love to hear from some cedar tub (unlined) users if they are out there about their experiences with Chlorine Demand. Are you able to maintain a 50% or better CD? Or will a cedar tub naturally be higher due to excess Chlorine attacking the wood after managing bathing load? I will keep checking back for replies. This seems like the best forum for spas in general, maybe not the cedar variety. 

Thanks

michael

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  • 7 months later...

I have just completed the order of a new custom cedar tub and eager to get going on water chemistry. I have read through plenty of forums, spoke with many different people around routine maintenance, and boy - it’s all over the map, especially when it comes to wood tubs. Many wood tub dealers recommend bromine and ozone solutions but I’m staying away from those and have invested in an ionizer and chlorine solution only. Mainly based on what I’ve read here.

 

I would love to hear a detailed regimen from first fill to daily/weekly maintenance. The tub is just shy of 750 gallons so I’d rather not “experiment” and have to dump all that water and start over. Our bather load will be 2 people 3-4x per week and 4-6 people 2-3x per month. I’m looking to maintain the tub for as long as possible while keeping a routine easy enough to manage each week without it consuming me. Who can show us the way?

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Ok. Wood tubs are not common, I have only worked on a dozen or so in 25 years. So I am no expert on them or how to best maintain them. I would say to do some research or follow manufacturers recommendations, but you have clearly done one and chosen to ignore the other. So I'll bite.

Lets start with ozone. Used for decades in multi-story municipal water tanks with great success, they were implemented into the aquatics industry. The first to use it in a portable spa was Dimension One, where it began a spectacularly destructive story. Ozone is not stable at normal uv levels. It is generated by exposing oxygen to high intensity uv radiation. Once it leaves the uv exposure it will remain ozone for a short time, around 20 seconds or so IIRC, before breaking down and reforming into oxygen. It is during the conversion from ozone (O3) to oxygen (O2) that free radicals or oxidizers are present (O1, if you will). If the ozone is in contact with water when this occurs, it will burn off organic contaminants including chloramines just like a shock. This means the ozone must be contained within a pipe for the full duration of it's life, which means a very long run of pipe. If released into the tub beforehand it only oxidises the cover, pillows, valves, and controller, while doing nearly nothing for your water. This was the case for a good decade in the spa industry before they figured it out. Some manufacturers still do this. Your whole tub is an organic contaminant. I would get some info on the ozone injection system before using ozone. Properly used, it is my favorite spa accessory.

I assume by ionizer you are talking about a mineral cartridge, filter, or floater and not an electronic ionizer? In an acrylic spa I can take or leave them. In a wood spa, anything that can cut down on oxidizers like chlorine, MPS, and bromine (to a lesser extent) are desirable. Do not use chealation or sequesterants if using a mineral purifier.

I suspect the lower oxidation potential of bromine is the primary reason it is recommended by the manufacturer. It also maintains at higher temps and is still an effective sanitizer even as bromide, whereas chlorine is not, once converted to chloramines. But it is not so easily oxidized as chloramines.

The manufacturer has to cover his posterior by recommending a system that is health department approved or risk liability in any mishaps. Such a system is generally overkill for a private spa with a cover. But I agree with them to some degree in this case. Bromine is probably going to be better to your wood than chlorine when maintained as a residual.

I normally recommend dichlor because it is ph neutral and easily oxidized. So it is ideal for a low dose at use treatment. It does build up cya, but as frequently as spas are drained it is not an issue. But it is a powerful oxidizer and could bleach out your wood.

Have you looked in to direct uv sanitizers? Also a good addition for low chemical systems. Often used in conjunction with H2O2 (hydrogen peroxide) injection in metal tubs and medical/ sporting equipment. Not sure how H2O2 might do in a wood tub, but nice because the only off-gas is oxygen. Very expensive system both to install and use.

 

 

 

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  • 3 weeks later...

Ryno and RDspaguy, good to see some activity here. Ryno congrats on your new tub. What maker did you purchase from? If you are interested, I have hooked up a 3HP variable speed pump to my system with 8 jets in a 500 gal tub and can give you some advice on plumbing such a powerful pump. I would definitely recommend this for your system or at least two pumps for the size of your tub. I have never maxed out the rpm on the pump and it can give a "punishing" massage, which we like! I found my tub on craigslist, it is from Roberts Hot Tubs, It has some issues but works fine. It may have had some deep contamination issues, which I am learning to deal with. I live in Ohio and had to place the spa equipment inside. So I have quite a long plumbing system ( about 25 to 30 feet overall). These tubs are beautiful! Best of luck to you!

RDspaguy, I would like to pick your brain about adding ozonation to my system. I have about have about 18 feet of 3" suction pipe prior to the pump, immediately after pump there is a three way that I partially open for spa use and close for filtering. The filter loop begins with a pentair 75 filter then master temp 125 gas heater then sunshine ionizer tee (copper and zinc) then the loop joins back to the main pipe to spa. You are recommending a long run for the oxidation cycle to take place in the plumbing and not the tub. Can I plumb an ozone generator in the suction line pre pump/filter/heater/ionizer? Is there a system you can recommend. How do I contain the ozone within the plumbing? 

 

 

 

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  • 1 month later...

I purchased my tub from www.redwoodsaunas.com out of Texas. I live in CA. The owner Jim was extremely helpful and guided me through the process and customization of my tub. Highly recommend them, courteous, patient, and a high quality hot tub. It’s 6 feet in diameter and holds around 700 gallons (42” water depth). I had it designed with 8 jets (2 each in four locations) and all the equipment resides in a custom enclosure that surround the tub. It’s absolutely beautiful and a focus in our backyard now. The pump is 2hp and all the plumbing is by waterway jets. Very happy with it. We filled it about 3 weeks ago, dumped the first batch of water and had the second fill now for 2 weeks. Still very heavy leeching. The first week we doubled the chlorine daily and added leisure time bright and clear each day to speed up the process of the leeching according to the manufacturer. On second fill, I added Pro Team Spa Gentle Spa for bather comfort and water stabilization and that appears to have worked well.

The ionizer appears to also be working well and I’m getting a residual copper reading of about 0.2ppm after a week. I understand this can take some time to build up but unsure how long. I balanced the water using a Taylor K-2006 test kit and my readings are as follows:

110 alkalinity (130-140 at first but balanced out)

7.4 pH

150 calcium hardness (used a calcium booster to achieve this as our CH was extremely low)

Adding about 1tbsp chlorine (dichlor) daily and after tubing. I’m averaging about 0.2ppm chlorine in the morning based on what I can read from the test kit. About 0.8ppm after 30 min of adding it.

I’m also debating increasing the chlorine due to a slime that I can feel on the benches near the walls of the tub and the outer edges of the floor that occurred yesterday. Not sure what it is. Worried about over chlorinating and pulping the wood but want to resolve the slime as well. I feel my levels are spot on and according to the test kit, it’s perfectly balanced.

 

Hopefully we can come together and find solutions for our tubs that other can benefit from and looking for any knowledge within the community.

436D1E98-2985-4525-B3B0-7A304605453C.jpeg

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Sharp looking tub!

Remember that dichlor is almost half cyanuric acid and at high levels (50ppm) it interferes with your chlorines ability to sanitize. If going with a higher dose you might want to use liquid chlorine.

You might consider a UV/ peroxide system. They are expensive to put in, and the 35% peroxide is sometimes hard to source, but the result is a chlorine free system with 0 gas-off (H2O2 converts to water and oxygen) and should be more wood friendly at normal usage levels than chlorine. They are used in medical facility therapy tubs and stainless steel and copper spas. Look into it.

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I have looked at alternative options instead of just using Dichlor but have not considered a UV/peroxide system. The only one that looked promising was switching to a dichlor/bleach method after you build up your CYA levels. How long that takes? IDK. This seems quite doable as bleach is inexpensive and can work without implementing any new "systems" being installed.

From what I understand, chlorine will attack the wood if there's no other bacteria for it to kill but it also burns off quickly and doesn't stick around like bromine would, which can lead to more damage of the wood even if used properly. I also like your suggestion about keeping ozone inside the piping as everything I've read causes issues in wood tubs. However, my plumbing run is extremely short as the pump/heater/plumbing is all within 15" of the tub itself, just a few feet of runs to get to each of the jets.

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Install the ozone injector (mazzei valve) on a bypass (tee before a valve in the main line) with a 3/4" tube running directly to one jet or back into the return plumbing after going through about 15 or 20 feet of hose. Use clear tubing sold at hardware stores not a garden hose. By using the bypass valve to control flow through the mazzie you can control how fast the ozonated water returns to the tub. Ozone has a sweet, fresh smell and you will know if it has returned to the tub too quickly by the odor and can adjust your valve accordingly.

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Ryno, beautiful spa for sure! I had a slime issue as well, which AH Some spa purge took care of when I performed a water change. I am concerned about your FC drop to .8 after 1/2 hour. I think it might be wiser to approach 2 ppm. I know the ionizer companies mean well but from from experience the .25 ppm is too fine of a line. I have been bumping my FC levels and I still find the FC demand is high. This may just be a cedar tub issue. Try adding Dichlor/bleach until your next morning reading is closer to 1 ppm.  I have not noticed any tub degradation with upping FC only residual chlorine odor.  

A not on the copper levels. Sunshine ionizers sells bottled copper ions in a powdered form to immediately bring levels up on fresh fill.

Following RDspaguy's advice I am researching an ozone generator, specifically CMP AOP Spa. I have tried to speak with a tech at the company but didn't find a knowledgable tech yet. I am fuzzy about about the installation and curious about a MDV unit post ozone generator that disrupts ozone prior to spa. I would like this to be an addition to the bleach/Dichlor/ sunshine ionizer that is currently used. I will either run a separate pump/loop or run it on a bypass line after heater/ionizer with its own return line. I find I am not a fan of the smell of the residual chlorine and like the fact that the ozone can eliminate the chloramines and keep chlorine use low as well these systems are supposed to take care of slime.

The UV-C 50 by Del is another system I am looking into that RDSpaguy suggests above. It is a high flow UV-C light system that does not add chemicals that can degrade the tub and can handle the high gpm of the spa pumps. It is a $500 addition but I would like some peace of mind. A small addition of ozone injected prior to the UV-C light produces Hydoxyls according to Del, which is more effective than ozone. 

Thanks for your input RDspaguy. I think we are on the right track. Cedar tubs may require a little more experimenting to dial in that perfect soak.

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I performed another refill on the tub and removed the slime build up with oxyclean and water. Rinsed and flushed. Brought water chemistry back to stable later that day. I went ahead and purchased leisure time algaecide to periodically treat any slime build up and will see if that does the trick if it returns.


I’m also still tinkering with FC levels and am finding it to be a challenge. I’ll add the recommended dosage (1tbsp dichlor for the 700g tub) and with the water nice and clear, I’m getting a reading of about 1.6ppm 30 min later, which was a bit better than my past readings on my initial 2 fills (probably due to leeching). Fast forward to about 8 hrs later and I’m getting a reading of zero. I want to add more but I don’t want to add too much as my thought process is the chlorine is attacking the wood and I just keep on dumping it in. Should I try to do a “shock” and dump in like a triple dose and get the FC levels to around 6ppm and see what happens and how far and fast the levels drop? I just don’t want to add too much as to cause irreparable damage to the wood. What are your thoughts?

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So I went ahead and did a dichlor chlorine shock to see what would happen. Tub was freshly filled 1 week ago so not worried about CYA but wanted to to get stable readings and a consistent CD. Added 1.7oz of dichlor bringing my chlorine level to 13ppm. 4 hours later my levels were 6ppm, 13 hours later it was at 0.4ppm. So my CD is definitely 100%. Brought levels back up this morning to 6.5ppm and will see how long it takes to disappear.


My guess is there must be something growing in the tub (although I can’t see it) or is it just attacking the wood? That amount of chlorine will inevitably damage the wood if I keep on adding that amount.

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Ryno,

We are in the same boat. Too bad there is so little input from the wood tub community. I am heading to the mentioned above UVC-50 from Del which is a high flow unit that can run any cycle from spa to filter, I will add an ozonator upstream that can run post bathing on a timer and not bother about ozone entering tub. Maybe a couple of short ozone cycles/day, along with chlorine as needed. 

My chlorine also hits rock bottom after a day and after some users got a rash I will make some adjustments. I think the addition of the uvc and ozone generator will do the trick. 

 

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So let's work out a new approach! We can thank RDSpaguy for his guidance. Maybe somebody else can chime in on the UV-C / Ozone solution. As soon as I have time I will try to find someone more knowledgable at Del to help us build a system for our cedar tubs. 

We have to appreciate that the CD will be high in cedar tubs, there is no way around it. Without acceptable levels of Chorine our tubs running at 104 F will become incubators for unhealthy organisms. Yet on the other hand we can't go overboard with ozone. 

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  • 1 year later...

Hey everyone. In New Brunswick Canada here. Have a 6 foot 700+ gallon cedar hottub. Use bromine.tablets in floaters....add some bromine granular from time to time....all going reasonable. 

 

I have had slime. Lately have been keeping it at bay. 

 

But current problem is a sour smell. Came out of nowhere. Did a purge cleaning..changed water....still there. 

 

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22 minutes ago, NB...er said:

Hey everyone. In New Brunswick Canada here. Have a 6 foot 700+ gallon cedar hottub. Use bromine.tablets in floaters....add some bromine granular from time to time....all going reasonable. 

 

I have had slime. Lately have been keeping it at ok bay. 

 

But current problem is a sour smell. Came out of nowhere. Did a purge cleaning..changed water....still there. 

 

Ours can get a little slimy from time to time but we use leisure time spa algacide and that does the trick for about a month, the ionizer helps throughout the process on a daily basis.

 

are all your other levels in balance? Are you adding anything in addition to bromine and water adjustments?

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I try and keep bromine tablets in 2 floaters. If it's used by more than one person I add a scoup of bromine after. I weekly add some non chlorine oxidizer....that's it

 

I built it myself....picture attached...

 

I am looking for things that are different as it worked without smell for 9 months. 

 

Lately I have been keeping bromine levels where they should be...3ppm. And before I barely kept 1.....it was difficult to.....maybe it's a bromine smell

 

I also had a hard time keeping pH correct but that has balanced. It seems when the wood was new it threw everything for loop

 

 

 

 

20210921_073509.jpg

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  • 8 months later...

Dang....was just getting good, and then no more info. I see it's an old post, but after a year or so I would love to hear what you folks have figured out.  I have a 700 gallon mahogany tub (refurbished original california cooperage tub from the 80s that was taken apart and put in dry storage for a couple decades. Needed some tlc in spots, but it holds water 100% leak free after less than 2 weeks. Running ozone generator, using dichlor as sparingly as possible, and using mineral stick in filter canister.  I know wood tubs are tricky and many opinions on chlorine, ozone, etc.  Would love to hear what you guys ended up learning, using, being happy with. Thanks! Doug

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