high PH+high chlorine

[p.p.h.]

10k gallon in ground pebbletec finish pool. I cant seem to get an accurate ph reading since installing the SWC. The taylor drop test kit has shows a 7.4 ph for the last 4 days. My PH is 7.4(taylor test kit) and the other (cheapy Pentair one builder gave me)says its 8.2(as high as it reads). My FC levels are 10. Pool water looks great. Should I drop in 2 cups of acid and see what happens? What should I do? Is it safe to run a higher PH with high FC levels?

[JohnT]

Most test kits are pretty good at pH. Your chlorine may be bleaching the color out of the Pentair kit. Often a kit has a chlorine neutralizer that you can use to check pH when chlorine is high.

[p.p.h.]

Is a PH test done with a DPD test kit known to bleach out with high chlorine and give skewed results?

[waterbear]

There is a problem with the phenol red indicator at high chlorine levels. Some of it gets converted to a different indicator (chlorphenol red) that will give a purple color at low pH! (the pH range that chlorphenol red is used for is 5.2-6.8!) The better companies usually include either a chlorine neutalizer into the indicator or as a separate bottle. This works up to a point but if the chlorine levels are very high it is still possible that your pH will read somewhat higher than it actually is. I would trust the Taylor reading since they DO include the chlorine neutralizer in their phenol red indicator solution. Taylor documents this in the pool and spa water chemisty book that they include with many of their kits.

I would not recommend adding any acid. Your pH is fine! The pentair kit is a perfect example of the phenol red converting to chlorphenol red which turns purple at pH above about 6.6! All this (pentair) test is telling you is that your pH is 6.8 or higher!

[p.p.h.]

thanks for your help. The water is crystal clear and there arent any visible problems so I wont worry about it then.

[Service Guy]

thanks for your help. The water is crystal clear and there arent any visible problems so I wont worry about it then.

That's not really the best logic. Clear water isn't always "friendly" water. Do like they say and get your CL level down and then retest the pH & Total Alkalinity. A characteristic of new plaster is the demand for acid to lower the alkalinity. Failure to accurately balance the water and bring down the alkalinity can cause a nasty build-up and do expensive damage to your plaster over a relatively short period of time time.

Don't assume because it's clear, that it's OK.

[waterbear]

That's not really the best logic. Clear water isn't always "friendly" water. Do like they say and get your CL level down and then retest the pH & Total Alkalinity. A characteristic of new plaster is the demand for acid to lower the alkalinity. Failure to accurately balance the water and bring down the alkalinity can cause a nasty build-up and do expensive damage to your plaster over a relatively short period of time time.

Don't assume because it's clear, that it's OK.

I might have missed something here but I don't think I have. Where did you get the idea it was new plaster? I certainly didn't. P.P.H. jsut said it was a pebbletec finish and the pH problem started when the SWG was installed. The problem he seems to be having is with his pH testing results. Also where did anyone in this thread say anything about getting the FC level down? P.P H. asked about adding more acid. FC level of 10 ppm is certainly not excessive if the CYA levels are high and are at shock level for a pool with very little CYA.

I just find your response a bit strange.

[PoolDoc]

My PH is 7.4(taylor test kit) and the other (cheapy Pentair one builder gave me)says its 8.2(as high as it reads). My FC levels are 10. Pool water looks great. Should I drop in 2 cups of acid and see what happens? What should I do? Is it safe to run a higher PH with high FC levels?

Taylor phenol red is partially stabilized against interference from chlorine -- up to about 15 ppm. I'm guessing that the phenol red in your 'cheapie' kit is not.

But, that doesn't mean that your Taylor reading is accurate, either. Unless you are using an FAS-DPD testkit (no pills, just powder) you do NOT know how high the chlorine is. With test strips, levels between 7 ppm and 30 ppm usually give exactly the same results on the strip!

Ben
"PoolDoc"

[p.p.h.]

Taylor phenol red is partially stabilized against interference from chlorine -- up to about 15 ppm. I'm guessing that the phenol red in your 'cheapie' kit is not.

But, that doesn't mean that your Taylor reading is accurate, either. Unless you are using an FAS-DPD testkit (no pills, just powder) you do NOT know how high the chlorine is. With test strips, levels between 7 ppm and 30 ppm usually give exactly the same results on the strip!

Ben
"PoolDoc"

Thats correct. The cheapy kit wants you to add chlorine neutralizer before adding the "red ph stuff". It says add 2 drops for chlorine levels above 3.0 for the cheapy kit. The Taylor kit you just drop 5 drops and swirl. im thinking my chlorine levels are alot higher than im reading.
So the solution to my problem is to get an accurate reading of chlorine with a kit that can read chlorine up to 20ppm 1st then maybe use the cheapy kit and put in maybe 4 drops of the chlorine neutralizer?? TA=130 CH=300 if that helps

[PoolDoc]

You can't just keep adding the chlorine neutralizer: doing so affects the pH test. Taylor has played around with it, and they tell me that they've stabilized the phenol red as much as they can, without screwing up the pH test.

PoolDoc