Is it normal for a pump to lose prime overnight even with no visible leaks?

[Zephyr]

For the last week, my pump keeps losing prime overnight. When I turn it on in the morning, the pump basket is almost empty and full of air. Once it finally catches, it runs fine the rest of the day. I’ve checked the lid o-ring, fittings, and connections and nothing seems to be leaking. What could make a pump lose prime only when it sits for several hours?

 

[syedsam]

For the last week, my pump keeps losing prime overnight. When I turn it on in the morning, the pump basket is almost empty and full of air. Once it finally catches, it runs fine the rest of the day. I’ve checked the lid o-ring, fittings, and connections and nothing seems to be leaking. What could make a pump lose prime only when it sits for several hours?

Losing prime overnight usually means a tiny suction-side air leak. Even a hairline crack in the pump lid or drain plug can suck air slowly. When the pump is off, water drains backward and pulls air in. Try greasing the lid o-ring to see if the seal improves.

 

[Manikshaw]

For the last week, my pump keeps losing prime overnight. When I turn it on in the morning, the pump basket is almost empty and full of air. Once it finally catches, it runs fine the rest of the day. I’ve checked the lid o-ring, fittings, and connections and nothing seems to be leaking. What could make a pump lose prime only when it sits for several hours?

Check the water level in the pool. If it’s even slightly below the midpoint of the skimmer air gets in once the pump shuts off. I had the same issue after a week of evaporation and topping up fixed it instantly.

 

[Freddie]

For the last week, my pump keeps losing prime overnight. When I turn it on in the morning, the pump basket is almost empty and full of air. Once it finally catches, it runs fine the rest of the day. I’ve checked the lid o-ring, fittings, and connections and nothing seems to be leaking. What could make a pump lose prime only when it sits for several hours?

Don’t forget the skimmer weir door. If it gets stuck in the up position the pump pulls water fine while running but when it turns off the water can’t flow back and the pump pot empties out. Happened to me last summer.

 

[Zephyr]

Good tips. I’ll look at the skimmer door and check the o-ring again. I didn’t realize even a tiny air leak could drain the pump pot overnight. Thanks everyone.

 

[Isabella Morales]

I’ve had my pump lose prime overnight too. It ended up being a tiny air leak on the suction side the O-ring just needed some fresh grease. Once I greased it, the pump stopped draining out overnight.