Hi Truckman;

This is the first time I'd looked back at this thread, since you posted the "100 CYA" info. That concerns me.

It *could* mean that you had much higher CYA, and now have only 100, and the CYA residue is eating the chlorine. But it *could* mean that your problem is all algae.

What worries me is that it's possible that you are getting fake chlorine readings, with is possible with test strips, and very likely with DPD tablet testing. So, please get a cheapie OTO (turns yellow) kit, and test. OTO is not very accurate, but it's bomb-proof. If OTO shows no chlorine; you have no chlorine of any kind. But, OTO turns orange at levels that bleach out OTO tabs, and turns brown at levels that screw up test strips.

So, please check. With CYA = 100, your liner can probably stand 30 ppm without damage, but you might be higher than that.

But . . . if you check with OTO, and your chlorine really IS low, then there's nothing for it besides repeated large doses of bleach, till the chlorine goes up, and stays up overnight. This is true regardless of whether the problem is algae, or CYA residure.

Ben
"PoolDoc"