what makes a pump lose prime?

[tagprod]

My pump today was not priming until I pulled the top off and put some water in. The pump is self priming and I've never had this issue in the two years I've had it. What would cause this?

I also went to help a contractor friend of mine who told the homeowner he could take care of the pool. He told them this because he's seen my pool and me messing around with it, and I told him, I'd help. Anyway same issue with this pump. This pump was much older - it had a metal lid and some screws you had to loosen to pull the top off. We had to work 10 to 15 minutes to get the pump to prime. Worked fine when we got it going. Does the homeowner need to get another pump or what?

 

[JasonLion]

The most common cause of a loss of prime is a leak in the plumbing. It is also possible for air to get drawn into the system through the skimmer if the water level is too low, which can also cause a loss of prime.

 

[jtm60]

air leaks into pump through sealed points/dried o-rings/gaskets..

 

[IkeRay]

first things first, I would re-lubricate the o-ring on the lid, also if you have the lid off of the pump basket for a prolonged period of time (like more than 5 min in some cases, sometimes shorter) enough air will get into the system to cause the "self-priming" to not work. in those cases, take a bucket of pool water and fill up the pump basket and immediately put the lid on, then flip the switch, it should catch prime.