Old pump too weak or too strong for new filter?

Pool pumps, pool filters and the plumbing of
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Old pump too weak or too strong for new filter?

Postby lotusflwr » Thu 29 May, 2008 11:03


When I bought my house, our 15x30x4 above-ground oval pool came with an old Hayward S166T sand filter/pump combo. I can no longer read the specifications of the pump, but the motor label says it's 1 HP.

I recently replaced the sand filter with a new Hayward Star Clear C500 cartridge filter, but the pump does not seem powerful enough to provide much return flow. The pressure reading on the filter is constantly 20 psi regardless of whether it is clean or completely coated with junk, and right after starting up with a clean filter the flow is respectable but quickly drops off to almost nothing.

I'm battling a mustard algae outbreak which I attribute to the very weak return flow causing little to no circulation in my pool. I tried hooking up my Polaris 65 pool cleaner to help with the circulation but the flow is too weak to push it around the pool either.

The pump and filter are located very close to the pool, no more than 6 feet. The only other equipment I have plumbed is an Aquatrol salt water generator.

The return flow of water to the pool is extremely vigorous if I run it without the cartridge in place, but as soon as I put the filter back in it's a barely noticable trickle. Is my old pump that came with the sand filter too strong for the 50 sq ft. cartridge or too weak?

Please enlighten me so I can figure out if I need a stronger or weaker replacement pump! Thanks :)

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