I'm guessing your volume to be a little over 7000 gallons. Adding 4 lbs. of stabilizer will add about 70ppm of CYA to your pool. Too much! Take the sock out. You report your range as being 30-50. Is there a reputable pool store nearby that will test the CYA for you? (You want a store that will use the 'disappearing black dot' CYA test.) That way you'll have a more accurate reading which will better enable you to decide how much CYA to add.

Get a good CYA reading first and then somebody here can make a suggestion about how much CYA to add.

Do yourself a favor and get a good test kit. The one we recommend is the Taylor K-2006 or 2006C (same kit, larger bottle of some reagents). If you buy it through the Amazon link in my signature, the Pool Forum makes a little money on the sale which helps us keep this form online. Only buy if the seller is Amato Industries, however. Some other sellers are substituting the K-2005 which you do NOT want. If Amato isn't listed, wait a day or two and try again. They seem to restock pretty quickly when they sell out.

Welcome to the Pool Forum!