This year I was using a solid winter poly tarp cover with a little giant automatic APCP-1700 1/3 HP 1800GPM pool cover pump left on the cover continuously in the automatic mode. After 4 months I found the winter cover drooped down 3 feet and I took the winter tarp cover off to find only 6 inches of water in the shallow end and 5 feet in the deep end. After spending tons of time and money trying to find a leak the conclusion is so far there is no leak. Pool repair mechanic told me the cover pump used is so heavy and powerful and the tarp, even though advertised as solid, still is fabricated with a weave, and despite being advertised as solid, still has some porosity (second year for this cover) so a strong heavy pump such as this one is able to pull the tarp cover into its bottom sump and vacuum water right out from the pool. He claims he has seen this happen many times and tries to make as many pool owners aware of this as possible to avoid wasted time and money with expensive testing. His remedy is to use a smaller and lighter cover pump or use the automatic pump intermittently and not to leave it on continuously. Does anyone else have a similar experience? Can this happen without a visible tear or hole in the winter cover?