Pump Losing Prime when Vacuuming

by Leo
(South Grafton, MA)

I have an above ground pool. I really don't know much about the history of the pool, it came with the house and the previous owners aren't terribly friendly.

I have replaced the plumbers tape on the skimmer hose fitting threads, and the pump fitting threads (Hayward Powerflo Matrix). I've put plumbers tape on the part of the skimmer and pump fittings where the hose attaches and tightened the clamps. The hose is new. I've replaced the o-ring on the pump (the one for the skimmer compartment).

I don't know what else to try. Could it be the gasket between the pump impeller and the motor.

Thank you in advance for your help.

Leo

Hi Leo.

Loosing prime when vacuuming could be one of several different things. These are some of the things I would check.

When attaching a vacuum hose I start by hooking one end up to the vacuum head and inserting the head, pole and pole in the pool. I take the other end of the hose to the pool return and let the water pressure blow all of the air out of the hose. When the bubbles are through coming out of the vacuum head I hook the hose up to the skimmer. Any air left in the vacuum hose when you attach it to the skimmer could cause the pump to loose it's prime.

If the filter is still pumping OK to start with check the skimmer hose and make sure it is not sucking air from any part of it left out of water. Check to see if the hose is collapsing anywhere. Strong pumps will collapse an inexpensive hose very quickly. A collapsed hose will usually cause the pump to draw in air from someplace and you will loose your prime.

Check also the hair and lint basket on the front of the pump. There should be no air bubbles visible below the lid. There should also not be a change from before hooking up the vacuum hose to after it is attached. The new o-ring would need to be well lubricated before using, something not everyone thinks of.

So, you want to make sure the hose is free of air before hooking it up. You want to be sure the hose is not collapsing and that the hair and lint pot is not drawing in air. Beyond that you could listen very closely for any air leak sounds when connecting the hose. That much air getting into the system can usually be heard.

Another tip for finding an air leak is that they will usually leak water when the filter is off. Leaky clamps and fittings on the suction side of the filter draw air when the filter is running and they leak water when the system is off.