Mike the Poolman


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Is your Sta Rite pool pump struggling?

September 10, 2022

Is your Sta Rite swimming pool pumps struggling to prime and pump water?
I’ve found that a common reason is a deteriorated drain plug o-ring. While other brands of pumps occasionally have this issue, Sta-Rite pumps are infamous for it.

While we don’t drain pumps in our area, pool owners in the mid-west and back east have to because of their extremely cold winters. A the end of the swimming season much of the country “close” their pools to prevent freeze damage to pipes, equipment and the pool itself. Among many tasks to complete the closure, drain plugs are removed from the bottom of the pump to allow water to drain out so it doesn’t remain in the pump and freeze (and as you probably know, when water freezes it expands and can easily damage its surroundings).

Sta-Rite is smart. To accommodate everyone across the country, they save money by using one mold for each of their pumps. People back east remove the drain plugs when needed but most of us in California never touch them because we don’t need to. But, when those pesky little o-rings degrade they leak and this causes flow issues.

How it works

There are two drain plug o-rings on most pool pumps: one below the pump pot and one below the pump volute. The pump pot is on the suction portion of the pump so when it leaks it sucks air into the pump and creates what we call a “vacuum leak”. Pumps don’t like air so even the smallest amount will affect the pump’s ability to prime and push water throughout the system. The other drain plug is below the volute and is on the “pressure” side of the pump.

Californians are more susceptible to pump o-ring issues because of our arid Mediterranean climate. We have low humidity and the dry air, well, dries things out. As these o-rings dry out they shrink and small cracks develop in the rubber. These cracks prevent a complete seal and minute amounts of air begin entering the pump. Most pool owners don’t notice at first because the pump is still moving water effectively. When enough air enters the pump a tipping point occurs and the pump struggles or fails to prime. Most pool owners check their pump lid o-ring and then put lube on it (I hate that!!) and then over-tighten the lid. Eventually they give up and call us.

How to troubleshoot

How can you tell if your drain plug is leaking? It’s easy on the volute (pressure) side because when it leaks, water drips out. It’s not as easy to see on the pump pot. When it leaks it sucks air. I don’t know how good your eyes are but mine struggle to see air! Sometimes when the pump is off water will leak out of the pump pot drain plug and it will leave a white stain (from calcium in the water) below the drain plug. It’s usually easy to see the white residue on the black Sta-Rite pump housing. If you see that white residue, get two o-rings and replace both drain plug rings. It’s very easy. The drain plugs thread into the pump so just unthread them, change out the o-rings and reinstall. Word of advice: don’t over-tighten! Finger tight only. If you over-tighten you’ll crush the o-ring more than necessary and you’ll prematurely wear out its elasticity.

Finally, don’t get me wrong, Sta-Rite pumps are phenomenal. They are neck and neck with Pentair for the best pool pumps on the planet. The drain plug o-ring issue Sta-Rite experiences can be corrected, they just need to use better quality rubber for their o-rings. When their o-rings fail do you know what I use? I replace them with the almond-colored Pentair o-rings. They can fail too but they are beefier and more hardy and I seldom see issues with the almond o-rings.

Best wishes,

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