Lost 3 feet of level over the winter

[tkzwolf]

Pulled back the mesh cover over my pool and noticed the level has gone down about 2 1/2 feet over the winter. The pool is in ground with a vinyl liner. The liner is 10 years old. The pool was closed professionally in the fall. THe water is green as it is every spring so I can;t see anything below the waterline.

I did not have any indications of a leak before the pool was closed as I only added about 2 inches of water all last summer. It appears that there is a leak. I suspect the leak would be a rip in the liner in the deep end or in the deep end drain. Any ideas as to what caused it or how to determine where the leak is?

[ChuckGeo]

Assuming that the water has leaked below the return fittings, the most probable location for a leak would be the liner, followed by the light niche/conduit, then the main drain sump. To locate the leak you'll have to fill the pool and get it cleared up, then physically inspect and dye test the liner, niche and main drain sump. Alternatively, given that the liner is 10 years old, you could take a chance and replace it, knowing that you may still have to address a leak in the niche or main drain. According to my calculations, your net loss was about 1.5" per week or less than 1/4" per day - pretty small leak, of course it could have dropped 2.5 ft. in the first 2 weeks than stayed at that level. I'd recommend a water loss measurement after you fill the pool but before you do anyhing else. Measure the loss from the pool over 24 hours with the pool off so you have some idea of the size of the leak your looking for.