Testing Ph with high Cl' levels?

How do you test Ph if the Cl' levels are 25ppm? CYA level is around 100 maybe a little higher. Raised Cl' up to 25 - 30 ppm to shock the algae. Ph was a little low before we started adding the 12.5% Cl. I did add borax before we added the Cl' to get it close to 7.2 range. Ran out of Borax.

I retested the CYA level with 50% pool water and 50% well water. Came up with 100 so that is about 200. I am not sure what level the CYA level is now.

This mornings numbers:

TA - 40
FC - 32 ppm
CC - 0
Ph - off scale low
CYA - ~200

I tested water again 6 hours later and FC levels have not changed. Originally I thought the CYA level was 100, that is why we tried to start to treat the water.

How much water needs to be drained and refilled to lower the CYA?

I came up with about 20,000 gallon pool with vinyl liner. 17' by 32' in-ground 3 foot shallow end to 8 foot deep end.

You can lower the CYA by 50% if you drain 50% of the water. Or...you can just run a high CYA pool, per Pooldoc's guide, which won't waste nearly as much water, and actually will make chlorine additions less frequent for you. Then as the water level is lowered by splashout and backwashing over the summer and topped off with fresh, the CYA will slowly lower itself. Of course, you need to stop using any form of stabilized chlorine (dichlor powder, trichlor tabs, etc.).

You'll need to wait for the chlorine levels to come down before you can get an accurate pH reading....

If you are going to maintain a high CYA level pool, how do you test for Ph? It should never come down to the range that would give good numbers. The pool came down from 32 on Monday to 25 today. Pool is still very green, how high can Cl levels go before they are damaging to pool liner?

I don't think the other numbers matter right now but here they are:

FC - 25
CC - 0
Ph last tested with lower Cl - 7.0
ph now - about same
CH - sample turned white after starting to titrate, don't think I need CH for vinyl pool however it does throw off the balance number not having any.
TA - 40
CYA - last tested around 200

Plan tomorrow was to put more Borax in, possibly two more boxes.
add three gallons of 12.5% to bring back up to 32 ppm Cl.

When your chlorine is high, and you test pH, you usually get falsely high numbers. So if your chlorine is high and you're still getting low pH, I'd go ahead and continue the Borax additions. You can dilute your pool water 1:1 with distilled water, test that for pH, and still have a reasonably good result up to about 20 ppm with the K-2006. So in your case, unless Pooldoc, chemgeek, or some of the others have better suggestions, I would treat with Borax until you get at least 7.0, then wait for your shocking process to be over and let your chlorine come back down to normal before testing it again.

Regarding your question about how high chlorine levels can go, I will tell you that I've had my chlorine up to the 30-40 range in my liner pool for a 2-3 week stretch, with my CYA at 90 with no problem. Since your CYA is so much higher than mine was, I wouldn't think that 30-40 in your pool would be a problem for your liner, (assuming both liners are the same quality) since the CYA acts to make the chlorine less aggressive. I wouldn't dare raise it that high if my CYA was, say, 20, but your higher CYA level is what makes you safely able to raise yours that high.

Just for my clarification--your sig says your pool is gunite, but you have a liner?

Janet

I am treating my neighbors pool that is a swamp. They have been paying the pool people to get them in a mess. So I told them about this site and said I would take on the challenge. My pool is gunite and clean sparkling water. Kids have been swimming a few times this year already here in VA. Neighbor was wondering how we got it open and clean so fast.

I was thinking that would be the case for the Cl`. I was thinking about keeping it at 32ish. I may take some water into work and have the Chemistry department test it for what ever they can. See if we are fighting anything else.