Water problems in small, small pool

[MikeFromMesa]

We recently installed a spool - a very small (about 1500 gallon) circular pool to allow us to get out of the heat in the Arizona summers. As I suppose is normal for new pool owners who have never had a pool before we are having problems maintaining water chemistry and those problems are probably more severe because the pool is so small. Our chlorine levels were so high that we had to cut our tablets in half not to drive up our chlorine levels.

We started using the pool about 3 or 4 weeks ago and, when I tested the water yesterday, I found very high CYA readings (> 150) as well as high (= 150) Total Alkalinity readings. I have read that the best way to get rid of high CYA is to drain and replace some of the water, but my real questions are (a) how did our readings get so high to begin with and (b) is high CYA dangerous to people. Our chlorine reading is also a bit high (about 5) but that may be low with such a high CYA reading.

The pool place near us recommended that we add muriatic acid to lower our Total Alkalinity but our pH is 7.6 and if I add the acid I assume I will also lower the pH. I guess I don't know how to get the values into a reasonable range to begin with so I can then try to maintain them.

Any suggestions? Thanks.

[Watermom]

Hi, Mike, and welcome to the Pool Forum!

Your high CYA is from those tabs which are presumably trichlor. High CYA will not hurt you but it will cause you to have to run higher than normal chlorine levels or you will constantly be battling algae. (Take a look at the Best Guess Chlorine Chart in my signature below for more about the connection between CYA and chlorine.)

If it were my pool, I would probably drain half the water and refill to try and lower the CYA level but that is only me. You may decide to just run the higher chlorine levels that will be needed. But, if you decide to do so, you will have to have a test kit that can measure chlorine levels higher than 5ppm which the Taylor K-2006 or 2006C will do. (Link in my signature.) In fact, even if you decide to do a partial drain, you should still consider buying that kit as it will make your pool maintenance much easier.

There is a guide to lowering alk. If you go to our sister website www.poolsolutions.com and click on 'guides' on the left hand side of the page, you will find directions for lowering alk. Also, please read the page about using muriatic acid safely.

[MikeFromMesa]

First, thank you for your reply.

> Your high CYA is from those tabs which are presumably trichlor. High CYA will not hurt you but it will cause you to have to run higher than normal chlorine levels or you will constantly be battling algae.

In reading some of the water chemistry stuff I have seen I thought I saw something that said I should turn to non-stabilized chlorine instead of stabilized chlorine. If I do that, and if I watch my chlorine levels carefully, will the CYA levels drop? Or must I drain and refill? I ask because I live in Arizona and water is a precious (and expensive) commodity. Our pool is very small, but if I am constantly draining and refilling my water bills will not reflect the small size of the pool.

I will look over the guide you mentioned before I do anything. And thanks again.

[Watermom]

Regardless of what you decide to do about doing a partial drain and refill or not, you must definitely switch to a non-stabilized form or chlorine such as bleach. No more trichlor tabs or dichlor shock powder. CYA take a long time to drop, so you are not going to see an appreciable change in it this year or maybe not even for several years. Having said that, in some pools, the CYA degrades over the winter into ammonia (which is another whole problem) but not in all pools and there is no way to predict in which pools this happens.

So, whether you partially drain or not, switch to bleach. But, you do need to order that good kit. Actually, even if you do a partial drain and refill, your CYA is still going to be around 75 or so and you will still need to be able to measure chlorine levels over 5, so go ahead and order it.

Let us know if you have more questions. We are glad to help!

[MikeFromMesa]

> So, whether you partially drain or not, switch to bleach.

I am going to partially drain this morning although I will only start with a relatively small amount to see what effect it has. The pool store guy suggested about 6 inches of water but I am unsure why draining such a small amount will have an appreciable effect. I was never very good at chemistry at the University but draining about 10% of the water would not, I would think, cause more than a 10% change in CYA. And, as far as the chlorine is concerned, yes I am changing to non-stabilized right now.

> But, you do need to order that good kit.

Amazon lists both the 2006 and 2006C kits. The first is about $50 and the second is about $90, but it gives no information about the differences between them. Do you have any information? I don't want to spend more than necessary, but I don't want to spend less than necessary either. If the 2006C kit is worth the price then that is what I would want to get, but I have no information about why it is more expensive.

I assume, based on your response, that the high levels of CYA in our pool are not dangerous to us as people and are not dangerous to the pool provided I keep the chlorine levels commensurate with the CYA levels. Is that correct?

Thanks again.

[Watermom]

You are correct in your thinking about the partial drain. If you drain half and refill with fresh water, your CYA level should drop by half. If you drain a fourth, the CYA level will drop by one fourth. In my opinion, unless you are going to drain a significant amount, don't bother because your CYA is still going to be high.

You are also correct that high CYA is not harmful but that you have to have higher chlorine levels as a result. The upside to high CYA is that you don't have to add bleach as often.

The difference between the 2006 and the 2006C is the size of the reagent bottles. The 2006 has .75 oz bottles and the 2006C has 2 oz. bottles which makes it a better price per ounce.

[BigDave]

The "C" version of the K-2006 has 2oz bottles of reagent. The regular K-2006 has 0.75oz bottles. So you get more than twice as much reagent for less than twice the price.