water shooting out of skimmer

[itismesue]

I have an AG 21 ft. round pool, and sometimes when I unplug the (Jacuzzi Laser Sand) filter, water shoots up several feet out of my skimmer. It doesn't happen all the time, but it does happen every third day or so. My pressure gauge never goes above the low teens, and otherwise everything seems to be working fine. The water is clear, I vacumn, backwash and rinse every week.
Any ideas what's going on and how to stop this from happening?

[duraleigh]

Interesting problem.

When you shut off the pump, it would seem the pressure in your filter is backing out thru the pump and out the suction line to the skimmer.

I can't quite figure out how it is only happening intermittently. Something must be causing increased resistance on the line returning to the pool from the filter but I don't know what that is. Others may have some insight.

[JohnT]

My guess is air somewhere in the system. Solar panels? Maybe just the filter. When the pump shuts off, the air uncompresses and shoots water out.

[itismesue]

We don't have solar panels with this pool. I have noticed that the pump resevoir doesn't automatically fill back up with water when I unplug the filter, but I do always take the top off of it so it can fill back up with water before plugging in the filter.