We have a 36 x 18 vinyl liner pool that is 2 yrs old. We have been losing water throughout both seasons but have continued to just add water. It is frustrating me as chemical balance is tough to maintain. I have done a bucket test and found we lost 1" (1/2 to evaporation and 1/2 to a leak) with the pump OFF. I then did the same test with the pump ON (closed the skimmer line and plugged it with a winter plug) and filtered through the main drain only. I lost 1" this time and only 1/4" to evaporation. Both tests were 24 hrs. There are no signs of leaks at the equip. I have went around the main areas (steps, skimmer, and lights) with dye and nothing sticks out. There is a bit of swirling in the pump basket when it first turns on. Usually if it is just the skimmer. Should I do the same test with the main drain off and just the skimmer? Will water still leak if the main drain is not plugged at the floor? Any ideas what this kind of loss is pointing to? Thanks for your help!