Polaris 380 slow in water, fast out of water


New member
Mar 19, 2020
Trying to troubleshoot my Polaris 380. I've rebuilt it within the last year including wheel bearings, belts, etc.

This past week I noticed it has started running slowly while running along pool floor. This is also the week of a heavy pollen dump by our oak tree.

I took Polaris out of water to do an rpm test. With cleaner in upright orientation suspended in water but not on bottom (as it would run along pool bottom) rpm slow (didn't bother counting).

However, with cleaner tipped over in horizontal direction outside of water (held up suspended over water) rpm were 32 rpm...as is normal.

What would cause the cleaner to run slow in upright position, and normal in "tipped over" orientation?

Backup valve operating normally, quick disconnect filter screen cleaned.

I also took cleaner apart, checked belt tension, looked for debris in jets, etc. Feedhose o-ring appears to seal well but havent tried operating the unit with top cover removed to verify.

Any guidance / suggestions / help is greatly appreciated.




Gold Supporter
Mar 21, 2016
Marrietta Ga
I had a 360 which ran off pump pressure and usually when mine acted like that my cartridge filter was dirty. ACted like it had enough pressure but not volume.
Does the 380 pump feed before or after the filter?