Quote Originally Posted by mortimay View Post
FC 6.9
TC 7.6
pH 5.0 <==
Alk 135
Stab 18
TDS 1400
Iron .12
Copper .74
Something is seriously wrong here -- I actually looked in your registration to see if you'd included a phone number -- but there are three possibilities:
  1. Your previous test results were all wrong, or
  2. You added a BUNCH of acid, but didn't mention doing so, or
  3. This most recent test is bogus and should NOT be trusted!

Pools don't mysteriously go from pH 7.6 (next to last test) to 5.0 (last test) for no reason. A pH of 5.0 *can* damage your liner. But if you didn't add acid, it's almost a certainty that the last test result is bogus, and should NOT be trusted. This means you should NOT add all that pH UP.

Ben