I have a 33,000 gallon vinyl liner pool.. I am testing with a TF100 testing kit.. I am very new & very stupid with all of this..my husband ( who unfortunately passed away ) always took care of the pool..my grandsons are trying to help me out because I've had 8 back surgeries & can't do it all.. I opened my pool earlier this year to find I had a broken line..grandsons sawed up concrete dug down got line replaced & I refilled pool for the 2nd time this season.. I tested my CYA & chlorine & pH...my CYA was zero..my chlorine was 3 on the basic test kit & my pH was 7.5.. I tried to put my signature in & this is the message I kept getting...We are sorry this content is not supported via the mobile style... Click here to go to the Forum Homepage.. I am doing this on my tablet..could that be my problem? I have some chlorine tabs & wanted to know how I will know how many to put in to raise CYA till I can get someone to take me to get the product to raise my CYA.. I don't want to get carried away & have to let water out as I've already filled twice this season.. I'm trying to do this right & I'm sure I have some alge in the pool..not as much as there was because I vacuumed to waste when I had to reduce the water level to replace the line.. I appreciate any help I can get.. Until I can get my signature in here are some stats..20 x40 vinyl pool..goes from 3 ft to 9 ft..there is 1 skimmer, 1 inlet & 1 return..there is no bottom drain.. I have Hayward single speed motor (about 5 yrs old) & a Hayward sand filter (about 4 yrs old) but has only been used 3 years because I was unable to open my pool 1 season because I broke my foot & ankle & was totally non weight bearing..this is where my alge problem came in..thanks in advance for your help