Difficulty Regulating Chlorine Input With Chlorinator And Stabilizer

by Jean

I am in charge of an hospital indoor pool. I have a chlorinator and regulating the chlorine has been difficult.The chlorine at that time was over 10ppm.

The stabilizer was over 400. I took out 2 1/2 feet of water then filled it up again. I took a sample to my pool company my ph and alk were within normal limits, my stabilizer went down to 100. (They told me it was livable)

At that time I did not add anything to help bring it down further.My readings are starting to fluxuate, where the chlorine is going up again, therefore I think I need a stabilizer that is quickly dissolved, so that the patients can resume their therapy.

Is there a natural additive? What can I do to lower the chlorine to 3-4ppm.

Thank you

Thanks for the question Jean

First I'll address the stabilizer, sometimes called cyanuric acid (CYA). Being this is an indoor pool and not subject to sun and heat, you might be able to forego using it. We don't use CYA at the YMCA indoor pool and the chlorine holds nicely. Some may say you need it but through personal experience it's an individual choice. For me, adding CYA to an indoor pool would be just an added expense. Check with your local and state laws for this.

Next is the 100ppm for the CYA. That is way too high. I don't know who you talked to about it being alright, but they are wrong. The CYA needs to be 7.5% of your chlorine. If you run the chlorine at 2.5ppm, the CYA needs to be at 33. Normal range is 30 - 50ppm. If you run the CYA at 100ppm, that means for the chlorine to be effective it needs to be between 7 - 8ppm. That's much too high for an indoor pool.

Perhaps you can try to dial the chlorinator down to about 5% - 10% or so. We keep the YMCA salt cell at 45%, but we get around 5000 swimmers per month. Normal chlorine range for a commercial pool can be 3.5 - 4.5ppm.

There are only two ways to quickly reduce the chlorine in a pool. First is a partial drain and refill, which you've done. 2nd is to use a chemical called Thiosulfate. This is a chlorine neutralizer. I don't know how big your pool is, but I used 10oz. in an 80,000 gallon pool to drop the chlorine level 1.0ppm. You can use that as a guide for your pool.

I would recommend doing a partial drain and refill first. Thiosulfate can get out of hand if it's not used correctly and may skew the chlorine reading.

Also remember that after adding any chemical you need to wait for 1 full turnover of the water before retesting. Taking your pool, I will assume it's considered a commercial pool, you probably are pulling around 250 gallons per minute (GPM).

This is the easy math. Say your pool is 50,000 gallons @ 250 GPM. That's 15,000 gallons per hour - 250 GPM X 60 minutes. 1 turnover would be about 3.5 hours. I would test after 4 hours to be on the safe side.

If it's not a commercial pool or the filter isn't pulling 250 GPM, you need to find the GPM and so the simple math to find out the turnover rate, then adjust from there.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.

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Hope this helps and have a great Summer.


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What About Bromine?

by Marti

Your site seems to discuss chlorine only. My pool uses bromine as a sanitizing agent.

Is there a reason you don't talk about bromine? BTW--your site is wonderful, and I want to use it, I'm just not sure it relates to my pool needs since you don't seem to talk about bromine.

Thank you for making your expertise available to the general public.



Thanks for the question Marti

I have been taking care of pools, clearing them up, installing filtration systems, etc... since 1999 and have had this website up since 2008. I have nearly 1,400 pages on my site and have answered nearly 1,000 questions. And your question is the first time I've ever been asked about bromine on my site. This is why I have no pages about bromine. It's a simple economic matter of supply and demand. There has been no demand so the supply is zero.

I like bromine and I think it's a good alternative to chlorine, especially concerning hot tubs because bromine has a better threshold when it comes to heat. I personally think it's a bit more of a hassle but if you're willing to put the work into it, finding the bromide ion reserve/bromine bank, following the 2 - 3 step process of proper concentration and adding an oxidizer on a regular basis, then I say go for it.

But, from a business sense, I need to deliver what people who visit my website want, and it seems to be chlorine pools.

Hope this answers your question and have a great Summer.


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