Quote Originally Posted by waterbear
CYA won't disappear that fast (in just over a week) unless you have drained and refilled or unless you have added a LOT of melamine (cya reducer, expensive, wastefull stuff) to the pool. Biodegradation by anerobic bacteria is a slow process and I really don't think it can reduce you from 80 ppm to 0 in that short a time. I vote for bad testing! Also the drop in pH with the rise in ALK on the last test looks suspicious to me.
TDS is a pretty much usless test and in a salt pool is alway going to be higher than your salt level which is a big part of the TDS!
Get the water retested. Or better yet get the $15 walmart kit that tests for CYA and test it yourself!
Your numbes show that the algae has possibly created a chlorine demand in your pool. That is why the FC is not holding. Do you have any numbers for TC? If the genterator is not producing enough chlorine then you probably had the start of algae and that was causing your FC to be low. Also the tests showed no salt on 5/4, 4000 ppm on 5/9 and then 3000 ppm on the next two. Unless you really had no salt and added a lot and then drained some of your water to get it down those readings are bogus. If you are relying on the readout on your SWG those readings could very well indicate the cell is failing. If they came from testing at the pool store their test practices are not very good.
Just my 2 cents.
I did add 300# of salt to get the salt up when I opened the pool. That explains the shift in salt....sorry for not posting that detail. I have backwashed twice and vac'd to waste once since then, so I've added some water, but at most at few inches lost and readded.

BTW...The pool has a nice green tint to it today. I hit it hard with chlorine tonight. Should I try to raise my ph with Borax? Should I hit it with polyquat?