Testing for TA with Thermal Pool Cover

Denniswiseman · Postby **Denniswiseman** » Sat 19 Nov, 2011 08:24

How long should the thermal pool cover be off a pool before testing for TA
I have had a result of 120-ppm with the pool cover just taken off and 100-ppm with it off all day
Obvoiusly both of these readings are OK but differ a lot
I don't want to leave the thermal cover off for to long to save on heating costs

Postby **chem geek** » Sat 19 Nov, 2011 13:41

There normally should not be any difference in the TA reading with the cover off vs. on or even after outgassing. Outgassing of carbon dioxide has the pH rise with no change in TA. So any drop in TA that you are reading is due to 1) testing error, 2) different amounts of mixing of surface and deep water with the cover on/off or 3) change in TA due to addition of acid (including use of Trichlor) or the FC dropping substantially.

Make sure you are taking a sample a foot or so below the water surface.

An FC drop of 14 ppm (say, after shocking a pool) would lower the TA by 10 ppm.

As for test error, make sure that you don't have static electricity affecting the drop size. Wipe the dropper tip with a moist cloth before starting the titration.

Denniswiseman · Postby **Denniswiseman** » Sat 19 Nov, 2011 15:14

Thanks for that, it has certainly cleared up a few questions regarding this issue