poor suction - new installation

Pool pumps, pool filters and the plumbing of
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jpadie
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Thu 03 May, 2018 02:55
My Pool: 12 x 5 rectangular; steps at the shallow side wall.
Magiline in-ground pool - filtration by cartridges.
1.5HP pump.

poor suction - new installation

Postby jpadie » Fri 31 Jul, 2020 15:48

Hi

i have just finished converting a magiline pool to a traditional pump and sand filter (with glass media).

filter: 22m3/h Hayward (762mm o/d)
pump: superpump clone (three-phase 1.5CV)

the suction is a single 63mm pipe (I imagine that the skimmers are aggregated into a manifold via some in-wall plumbing). There are three returns @50mm and one at 25mm (for a polaris robot).

In the past, when the 1HP magiline pump was installed, there were visible whirlpools in each skimmer and the returns were too powerful to put my hand against and hold it there. Now, although I think that the returns were a little blocked with debris after two years without use, the flow is only strong against my hand if I isolate a single return.

The pump sounds as though it is straining somewhat; but then again I don't know what three phase pumps sound like (my previous was a single phase - I'm now using a VFD).

As of today there is no non-return valve on the suction, and the pump inlet is about 40cm above the pool level. Tomorrow I will install a non-return. But I don't think that is the issue as the absence of a non-return should not limit the suction once the pump is primed.

There is no suction leak in the plumbing that is exposed. However the pressure inside the filter is not rising as quickly as I'd expect. After about an hour, it was at 5psi.

Can anyone suggest things to check? I wonder about debris in the suction lines - but if that's the case then I'm very unsure how I can clear that. Difficult to swap inlet and outlet on the pump as they are solid pipe. The VFD says it can reverse the motor direction, so perhaps that is an option?

any advice very gratefully received.
thanks
Justin


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