Wow, after finding this forum thanks to suggestions from another forum I read, I am almost sick about how we have treated our pool and how much money we have poured into chemicals we didn't need! We have a beautiful free form vinyl pool which was built by a highly reputable pool company in our area. When the pool was done they gave us a two way test kit, PH up, PH down, dichlor and a bucket of 1" trichlor tabs to put into our autofeeder and left us to our own understanding. Now I see how we messed up!
The first two years were great and the pool held chlorine. Last summer was very hot for our area and we could not keep chlorine. We added so much shock and had floating trichlor baskets trying to keep the chlorine where it should be. The pool liner faded where the baskets floated, so we ruined the look of our beautiful blue liner. Then we paid to have the pool closed as usual and we were shocked to find it completely nasty green this Spring. Now after reading here about how CYA builds up over the summer, I am sure our CYA numbers were off the charts last fall. So, adding enough chlorine to get thru the winter probably didn't do a thing because the high CYA rendered it useless. Thus a nasty nasty mess this spring. To clear up the mess the pool store sold us tons of chlorine, dichlor, calcium up and alkalinity up!
So, I am about to go drain my pool down to get the CYA under control. I have a shed with trichlor 3 inch and 1 inch tabs I can't use. Totally bummed right now. Wish I had known all this stuff 4 years ago. I would not have had to refer to pool maint. as "fighting with the pool". So thanks for the useful, unbiased advice which I can hopefully begin using and get the pool treated right!