Solar Pump Installation

Some pumps are not self priming and need to be below the water surface....
Some pumps push better than they suck too.

My pond pump (mains powered) doing a similar task, sits at the bottom of the lower pool to do the job.

Del ( PS. The Frogs say 'hi' )

If mounted above the water, does it need priming? could there be an air leak? My pump is also submersible, so it doesn't have to suck.

This topic sucks. <Splutter>

If the pump is large enough for your application, and I assume it is, then I'd look for a leak, it may be sucking air.

I would ask, has it ever worked well?

If your answer is no then I say you have a couple of things to consider.

1. Certainly check for leaks.

2. You are at a lost from the beginning because you have no NPSHA, so I would put a "trap" in the pump line and maybe a check valve to hold a porition of water as close to or above the pump inlet to "prime" the pump on start up.

The lack of net positive pump suction head available has to be over come to achieve reliability. Is it possible to bring the pump down closer to the water level or simply install a submersible pump in the lower pond?

Mike

Yes U are right.

Thank you Ducon

You are right.

NPSHA ????

Pumps work well if the it gets +ve suction head. i.e the suction is below. On above as in your case, it is -ve suction head and will give you problem. It needs first a foot check valve at the suction tip and needs to be primed before starting.

Note. If you do have a foot check valve at the suction tip and still facing problem then that must be leaking. Take it off, clean or replace.

May be you have designed and installed your pump with a NPSH_A less than the NPSH_R. May be reducing the height of 1 m to become 0.5 m or less, may be help in working properly. Or may be the power of the pump is insufficient.

The answers given so far are all related to the suction problem. Have you considered the possibility that the pump is not capable of overcoming the discharge head (pressure)? There is also the possibility that the discharge is "air locked". Is there a way you can open the discharge line to air and see if the pump delivers then? Perhaps a pipe connection not too far downstream from the pump can be "cracked" to allow the discharge to flow there. As for the NPSH of the pump, one meter is far below the NPSH of any pump with which I am familiar. Required NPSH is customarily quite low, especially when operating on the left side of the characteristic curve of the pump. I would discount that as an option. The "foot valve" is a good idea because it will hold the prime of the pump after it stops. However, as stated by others, the pump must be manually primed to get it started. The most probable culprit is, as some have suggested, air being allowed to enter the suction side of the pump. Check your connections, prime the pump and see what happens. Good luck!

Have you considered the possibility that the pump is not capable of overcoming the discharge head (pressure)?

No

That is acceptable point, why not?

Some pumps also have check valves in the head that need cleaning sometimes or even reseating. But as always the easiest fix would be to check the prime.