Podcast Q&A 9: Can I Use Pool Chlorine Tablets to Treat My Storage Tank?

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Hello. Welcome to the Clean Water Made Easy Podcast Question and Answer Episode 9.

My name is Gerry Bulfin. I’m a WQA-Certified Master Water Specialist and Water Treatment Contractor here in Santa Cruz, California. We get a lot of phone calls, emails, and chats through our website. For this, I’m  picking the more interesting ones and put up a quick answer to the question.

We received an email from Goldie who wrote:

“My husband has been using pool tablets on a weekly basis in our 3000-gallon holding tank. Our water no longer has the faint tea color from the tannin in it. However, I can smell a strong chlorine smell in the shower and toilet. I do notice a drying effect on my skin. What I’m most concerned with is the effect on our septic tank. Is it safe to use pool chlorine tablets on a regular basis without damaging the septic system?”

Goldie thanks for your email. The pool tablets will be effective for the tannins. They’re releasing chlorine into the water.  I know you’re asking about the septic tank, but normally we do NOT recommend pool chlorine for potable water. Even if you are not drinking the water, it’s not the best even for bathing in it either.

Pool Chlorine is for Pools, not Drinking Water

There are some pool chlorine that are also certified for drinking water; but usually, most of them are not. They are not made for drinking water, they are made for pools.

To give you an example, you can look and see on the bottle or canister what type of chlorine it is. The common chlorine that is used in drinking water is solid and is calcium hypochlorite. Then when you put it into the water, you’re getting the chlorine, and a little bit of calcium, but nothing toxic. Other than the chlorine which at certain levels is toxic, but that’s a topic for a different day. Chlorine is very effective so they’re using it.

Anyway, calcium hypochlorite is what you want for drinking water. When you get into pool chlorine, you get into trichlor and the dischlor type which contain cyanuric acid. Generally, though it sounds like cyanide, it doesn’t give you cyanide poisoning. However, there could be other contaminants in the trichlor and the dischlor chlorinating compound. It’s not good for potable water.

Lithium hypochlorite is another one that’s used in pools. That’s something you would want to absolutely avoid because lithium toxic. There are some trichlorides and dichlorides that are certified for drinking water but I’m not sure exactly how toxic it is but usually we won’t recommend the pool chlorine tablets for potable water because you can get the regular tablets. They’re not that expensive and lasts a long time. We carry one that’s been NSF certified for drinking water but generally, the chlorine pellets that are made for drinking water is the best one.

You mentioned 2 things – dry skin and your septic tank.

Getting into the septic tank, we generally do not recommend a constant high chlorine residual going into your septic tank. It can slow down the bacterial growth in your septic tank and prevent it from becoming a septic tank so you don’t get that septic action. You’re better off getting the chlorine test kit and just add a tiny bit of chlorine so you don’t have a huge residual. We generally wouldn’t want to put more than .2 or .4 parts per million chlorine residual down your septic tank. That’s what we’ve been told by septic guys. They generally want to avoid using chlorine bleach but in the use of chlorine bleach in the laundry, we generally do it like a one-shot thing it’s not putting that constant amount of chlorine down the septic tank. It’s not that it would completely ruin your septic tank but it would stop it from doing what it’s supposed to do which is to digest the sewage. So you want to avoid that.

There is a way to usually deal with that which is to inexpensively get a small tank of carbon and as the water flows into the house, it flows into the carbon filter, removes the sediment, takes off chlorine and then once a week backwashes and cleans itself. Or you can get just the carbon cartridge, which is not the best thing for the whole home. You don’t get as high a flow through it but you can use that. Or one of these small carbon filter tanks.

This also would have a big effect on the drying of the skin. Chlorine dries out your skin, dries out your hair. So the idea is if you put a carbon filter for your home, whole house, you’re going to be removing the chlorine and also if there’s any tannin left in the water, the carbon would help with that. But if this is working for you, it’s definitely the lowest cost way to go because you don’t have to buy equipment.

Generally, we recommend, if you can do it, is to get a small chlorinator so when your well pump turns on and is filling the storage tank, it’s pumping a tiny bit of sodium hypochlorite or calcium hypochlorite mixed with water. Either way you have an NSF-certified potable water-grade chlorine at just the right amount so you can regulate, so you don’t get a huge residual.

And when you’re dosing your tank you say you’ve been using pool tablets on a weekly basis so I gather from that that you might be just throwing the tablets into the tank?

Throwing it into the tank you can get a high chlorine residual and then no chlorine residual. That’s another thing. Having an automatic chlorinator is better but people do what you’re doing. It works great but just be a little careful about using the pool chlorine. Look on the bottle and see what kind of chlorine it is. If it says lithium I would avoid it. If it’s one of the trichlor or dischlor, they’re not for potable water but some of them had been certified for it and they claim that the cyanuric acid part of it is not toxic. Generally, in the role of water treatment, we recommend potable water grade.

Okay. That was a really great question. Thanks for asking that.  If you have a question just please go to our website, cleanwaterstore.com. You can see a little chat box there. You can chat with us or better yet, give us a call or send us an email. Email me directly at [email protected]. Thank you.