My buddy just bought a ranch with a small, fiberglass in-ground pool. The Polaris 280 had been working fine. I went out yesterday and it was barely moving and listing on the side. I took it out and made sure all the swivels were tight and everything seemed OK. Put it back in and it did the same. Looked at the filter and the pressure was a little high, so I did a DE reload thinking the return pressure may have been too low. This pool does not have a booster pump. Any suggestions?