Low Ph And Chlorine

[rickai]

All,

I've got two issues: FIRST: I used PH minus to remove some stains in my pool. My PH dropped to 6.2, stains were gone, and now I've been using PH plus to get the PH back up. I've used ALOT of PH Plus, but it doesn't seem to want to come up past 6.8...in fact, it will come up for a day or so, then head back down. I've put in about 8 lb of plus...but it won't stay. I could use some advice.

SECOND: The chlorine also doesn't want to register. I know it's in there because I can smell it in the pool we've used a ton of tablets. We have a new test kit, so I'm pretty sure it's not the testing solution. I've also used the test strips and they say pretty much the same low reading. Is this related to the first issue? Thanks for any help!

[tkalla2000]

You may have to much chlorine in the pool. When you use the liquid test, does it get dark when you put the first couple of drops in and then go clear by the fifth drop? As for the PH, check your Total Alkalinity and adjust it to 100 - 120 and then adjust your PH

[rickai]

Thanks for the info. I may have too much chlorine, but if so, it's not registering as such on my tests. Is there something that makes it not show up?

Also, I dumped a ton of PH Plus in tonight and got the PH up to 7.2 . I will test tomorrow night and see if it's dropped again. Also, the Alk was around 75 (low), so does that throw of PH or chlorine readings. Figuring out the relationships to all these tests is pretty hard. Anyone with help is welcome. Thanks!

[chem geek]

The DPD chlorine test, which is where you compare the color of pink/red vs. a standard, will bleach out above 10 ppm Free Chlorine (FC) making you think you have no chlorine when you actually have a lot. You can buy a very inexpensive OTO chlorine test where you compare the color of yellow/orange vs. a standard as this will not bleach out, though it will not distinguish between Free and Combined Chlorine. The best test to get is a FAS-DPD chlorine test where you count the drops to determine more precisely (to 0.2 ppm or 0.5 ppm depending on sample size) the amount of chlorine and this will not bleach out (if you get a flash of pink you just add more powder).

[rickai]

Thanks Chem Geek. I'm using the drop test and it shows no chlorine or very low chlorine. And the PH tends to be drift low. Does that make sense? I dont' think it is a bleaching problem, do you? Thanks again!

[chem geek]

Thanks Chem Geek. I'm using the drop test and it shows no chlorine or very low chlorine. And the PH tends to be drift low. Does that make sense? I dont' think it is a bleaching problem, do you? Thanks again!

When you say you are using the drop based test, do you mean you add 5 drops of indicator and compare how pink/red it is to a standard? Or is it a true "count the drops" FAS-DPD chlorine test where you add some powder to make the sample turn pink/red and then add drops counting them until the sample turns clear?

[rickai]

I'm using the 5 drops test. It has a chlorine test (yellow) on one side and PH (red) on the other. Thanks for the help!

[chem geek]

I'm using the 5 drops test. It has a chlorine test (yellow) on one side and PH (red) on the other. Thanks for the help!

OK. The 5 drops of indicator and then comparing the shade of yellow/orangae against a comparator is called the OTO chlorine test. It's the least expensive, but has the advantage that it will not bleach out. It really measures total chlorine so does not easily distinguish Free from Combined Chlorine. In any event, if it remains clear, it means you don't have chlorine (especially if you wait a few minutes after adding the 5 drops and it still remains clear and doesn't turn yellow).

If you are using Trichlor tabs/pucks, then these are slow to dissolve so you could have a nascent algae bloom consuming all the chlorine. It could be that your Cyanuric Acid (CYA) level is high making the chlorine less effective. I would shock with chlorinating liquid or 6% unscented bleach. You should also get a good test kit such as the Taylor K-2006 kit you can get at a good online price here or the TF100 test kit from tftestkit.com here with the latter kit having 36% more volume of reagents so is comparably priced "per test".

Your continued use of Trichlor is what is driving down the pH. These tablets are very acidic.

[rickai]

Is there anything I can do to combat the acid being introduced by the Trichlor Tabs? Also, I shocked with Liquid chlorine and the chlorine level came up to 2. Thanks for the advice.

[chem geek]

Is there anything I can do to combat the acid being introduced by the Trichlor Tabs? Also, I shocked with Liquid chlorine and the chlorine level came up to 2. Thanks for the advice.

The normal approach to handling the pH when using Trichlor is to have a higher Total Alkalinity (TA) level (usually 120 ppm or so) since the outgassing of carbon dioxide from the pool will raise the pH counteracting the drop in pH from the Trichlor. The extra TA will also help buffer against the pH swings. The net effect of this is a slow drop in TA over time so you'll need to compensate for that. If both the pH and TA are dropping, then you can use pH Up or the equivalent supermarket item of Arm & Hammer Super Washing Soda (careful: NOT the laundry detergent). If only the TA has dropped, then you can use Alkalinity Up or the equivalent supermarket item of Arm & Hammer Baking Soda.

A bigger problem with continued Trichlor use is that the pool will build up Cyanuric Acid (CYA) since for every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases CYA by 6 ppm. So unless your pool is very small, has a DE filter you backwash weekly, or that you regularly dilute via partial drain/refill, then the CYA level will grow over time. This makes the chlorine less effective unless you proportionately increase the FC level to keep the FC/CYA ratio constant at a minimum FC of 7.5% of the CYA level if you want to prevent algae growth. Otherwise, you'll need to use a supplemental algaecide such as a weekly dose of PolyQuat 60 or a phosphate remover.

Richard

[rickai]

Thanks for the help. So, if TriChlor causes all of these issues, what is the best way to keep my pool chlorinated and in balance with out all of these side effects?

[chem geek]

Chlorinating liquid (usually 12.5% or 10%) or 6% unscented bleach will add only chlorine and some extra salt and that's it. You could also use Lithium Hypochlorite powder/granules since that is similar, but it's very expensive. All other sources of chlorine have other serious side effects (even chlorine gas used only by professionals doesn't add anything extra, but it significantly lowers pH). The following are chemical facts independent of concentration:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.

For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.

For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.

So you can use the above products that add to CYA or CH in the short-run, but eventually need to compensate for the increase via dilution or in the case of CYA with use of a supplemental algaecide (e.g. PolyQuat 60) or a phosphate remover to prevent algae growth.

Unfortunately, adding chlorinating liquid or bleach is not as convenient as Trichlor since you have to add it every day or two unless your pool has an opaque pool cover in which case you can usually add it twice a week. There are automated chlorine dosing systems, but the least expensive one called The Liquidator has pros talked about here and some cons of "white stuff" deposits that about a third of those with the product get here. Other options include a peristaltic pump or a saltwater chlorine generator (SWG) with the latter being very popular though more expensive.

You can manage a pool using Trichlor, but you need to control the pH and the CYA level or algae prevention technique and this usually costs more -- that's the tradeoff of price vs. convenience.

Richard