Water Temp affect test?

spthomas

Active member
Mar 24, 2014
36
Lewisville, TX
I purchased a FAS-DPD test kit (Taylor) last summer and used it through the warm weather and things were fine. For the winter, I've been doing quick tests with strips. So today I decided I should use the better kit and test everything. When I did the DPD test for Cholrine, the sample remained clear. I originally used 2 scoops as directed, and i added 3 more scoops of the DPD reagent and still the sample was clear. Ok, so maybe there is NO chlorine in the pool? Anyway, I moved on to the Ph test, and it shows just a tinge of color, around 6.6 ph. That doesn't really seem right. For the 15 years I've had this pool, I often add acid to lower ph, but it's never been low like this before, and I haven't added acid in 3 or 4 months.

So, I tested with the test strip, and it did show no chlorine. But it showed high PH around 8.0, which is what I would have expected given I haven't added acid for a while. The test strips are not as accurate for sure as the FAS-DPD kit, but the results have generally been close. So I'm looking for the reason for these results. As I said, I purchased the Taylor kit last spring, and it is not expired, and neither are the strips. So could it be water temp? I did have a bit of algae (even though the water temp is 48 I had a bit of an algae bloom on the steps close to the surface, where I guess the sunlight heated the step).

Steve T
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
23,437
Laughlin, NV
Make sure you used the correct reagent to test the pH. With a high TA it is very difficult to have a pH lower than in the 7’s.
 

spthomas

Active member
Mar 24, 2014
36
Lewisville, TX
The reagents were right, and being very careful with drop counts I can see it was off a little. But I still have Ph about 7.2 with 120 TA. And zero chlorine, so the tablets in the floater are not dissolving in the cold water (56 degrees fahrenheit). That's the first time I can ever remember the ph being low. It's usually trending high, and I have to add acid.

So what do I use to raise the PH that won't also raise TA?

And another comment. I've used test strips the first part of winter since the water is relatively stable in the cold. But the strips consistently tell me my stabilizer is low, even after I add it. When I used by Taylor kit, stabilizer is around 80ppm. So the strips were WAY off on stabilizer for some reason.

Steve
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
23,437
Laughlin, NV
Aeration will raise the pH. I would not chemically raise the pH with that high of TA.

Strips should just be thrown away. They are not reliable nor repeatable.

Better to add liquid chlorine once a week or so to maintain FC levels based on CYA.
 

spthomas

Active member
Mar 24, 2014
36
Lewisville, TX
Sounds good. The chlorine level was ok for a long while this winter, as long as I added a gallon of bleach every month or so. But the weather is getting warmer and I think the temperature and algae bloom depleted it.
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
859
Spring Valley, NY
I've had the experience in the past where testing wasn't consistent was due to residue left from previous testing. As per TF TEST KITS advice I cleaned the vials well and used alchohol to wipe out the insides of the testing vials and rinsed well with water. Be careful not to remove the vial calibrations, ask me bu ow I know. Also the TA test has a static component so follow instructions to the T as the outcome may be what you're experiencing.