Cloudy pool, pH seems locked

[HokieMatt]

Hello all,

I have lurked here for years and gotten plenty of good information. I've come across a water problem now that I could use some help with. I am in central CT and opened my pool before Memorial Day. IG vinyl, ~25,000 gallons, 1.5HP SuperFlo, Hayward C4025 cartridge filter, Polaris AutoClear Plus SWCG, Polaris 280. It was the usual greenish spring mess on opening, but cleared up in about a week as it does every year. Then the weather turned cool, so I reduced the runtime on my pump to about 8 hours (I do this in the fall too, when usage falls off - never had a problem). Over this past weekend I put a new solar cover on it, then the weather warmed up this week and a couple of days ago the water turned cloudy. Nothing terrible, I can still see the drains in the 8' deep end, but it's not as clear as it should be. Tested the water and found:

pH 7.2
Alk 80
Cl ~1PPM
CYA ~50
CH 150

I figured the chlorine was drifting low due to the reduced runtime and increasing sun load, so I increased runtime to 14 hours and added 1lb of 68% cal hypo shock. I also added about a pound of soda ash to try to get the pH up a bit. Subsequent testing showed no change in the pH, alkalinity up to 90. I tried using Taylor base demand reagent and added 10+ drops with no change in the test color. With my relatively low alkalinity this struck me as very strange. My first thought is simply that the base demand reagent spoiled - it's 5+ years old and I'm not very diligent with keeping the kit in a controlled climate. However even if that is the case, what could cause the pH to lock up like that without high alkalinity? Other than the shock and soda ash, the only other thing I added was 4oz of clarifier in an effort to clear the water. I thought maybe some of the other reagents could be giving false readings, but I have no reason to believe I have high alkalinity given the amount of rainwater the pool received over the winter and spring. Fresh test strips more or less correspond to the kit readings also.

Also, is it likely that the cloudiness is simply due to insufficient runtime on the filter, and it should clear up on its own in a couple of days given longer runs? Maybe there was some dust/grit/whatever on the new solar blanket?

[aylad]

The cloudiness can come from inpending algae, dust/pollen on the blanket, dead algae that needs to be filtered, too much cal-hypo added too quickly, or a host of other things. To rule out goo in the pool creating the chlorine demand, I would test my water at night for chlorine and CC, and test again in the morning before the sun is on the pool. If more than 1 ppm of chlorine was lost in non-sunlight, and/or the CC was over 0.5, then I would shock the pool again and hold it at shock level until it passed that test. If there was not more than 1 ppm chlorine loss, then I would look to the filter to filter out whatever was causing the cloudiness.

I would not worry about the pH at 7.2...that's fine, and the nature of a SWCG tends to run the pH upward anyway--I would leave that alone and not worry about it. I would also keep my chlorine levels higher than 1 ppm, to make sure I wasn't fighting algae all summer....

Welcome to the forum!

[HokieMatt]

I normally run around 3ppm and never have algae issues. I noticed the Cl level had dropped and I attributed it to the reduced filtration/SWCG runtime combined with rising temperatures and more sunlight.

I'm going to have a hard time letting the pH thing go, I need to know why the soda ash didn't raise it. I haven't added CYA in weeks and don't use dichlor/trichlor or any other acidic chemicals, so I'm puzzled as to what could be offsetting the pH increaser.

[aylad]

OK, suit yourself....

We try to keep people from "chasing numbers", and just get the water balanced right for a clean, clear pool that they can enjoy. However, I realize that to some, the pool becomes more of a hobby than the swimming. So...I won't try to answer your pH question. There are some chemists on the forum who might. However, right now we're all pretty swamped trying to help people who are trying to get their pools swimmable, so you may or may not get another response on why youre pH isn't rising. I hope you understand :)

Janet

[HokieMatt]

No problem at all, I realize my "problem" really isn't one at this point. I've ordered a new K2006 test kit, once that arrives I may well find out that all my readings were bogus due to expired reagents.

To update my water situation, you were right about the impending algae. A couple of days ago I checked chlorine level in the morning before the SWCG was running and found it at zero. Brought it up to about 10 with cal hypo shock and kept it there for 24 hours, after which it was crystal clear and has stayed that way for 48 hours with no other chemical additions. Chlorine level holding overnight, so it looks like the problem is solved. Thank you for pointing me in the right direction.