Very Interesting Problem

[duraleigh]

Well, I have seen the miltary blamed for many things but not TDS in pools....I believe that to be a stretch, to say the least.

It actually sounds like you're describing a build-up of Combined Chloramines in the pool. They will test positive on a TC test (OTO) but do not register in a FC test.

The solution is exactly what you are doing....breakpoint or "shock" chlorination.

The key to preventing this is to test for FC and CC with a good FAS-DPD. If you test at any time for CC and get a result greater than .5ppm, it is generally time to "shock" (superchlorinate, breakpoint) the pool. That will burn off the CC's and return all the Cl in the pool to FC.

Do you think that describes the issue?

TDS levels less than 3000 are generally disregarded by most folks....are you measuring TDS higher than that? Additionally, I don't believe superchlorinating has any effect on TDS so if superchlorinating solves the problem, I don't think it can be TDS.