Ian Stirling wrote:
John Laird wrote:
hzatph wrote:
It can be tricky. Have you tried flooding the outlett hose while the pump is
running? Put a hose pipe or similar into it. I know that initially you will
be opposing the pump, but it will flood the impeller and once it is flooded
you can remove the hose pipe and it may pump out as you intended.

I had thought of either attaching a wet vacuum to the outlet and
sucking the damn air out, or trying, as you suggest, to force water in.
I suspect the latter will only push water out the bottom of the pump
though - it's open to the water that the pump is sitting in.

The impeller is, weakly, pushing water out. But a finger over the
outlet can stop the flow, so it's really only just catching water.

Generally, if you can get enough water through it, it'll put lots of
little air bubbles in that flow.
This removes the gas from inside the pump.

You'd think, wouldn't you ? I've left it running for a couple of
minutes with no success, jiggled it about to try to move the internal
water about, and plugged and unplugged the outlet to try to disturb the
water/air mix inside. With no success. It needs depth of water, pure
and simple. When in enough water, a few seconds is all it takes to
expel the air pocket and start pumping properly.

If I felt sufficiently adventurous, I could remove the impeller and
stick something on it to increase the turbulence slightly. It may be
the generated flow is too smooth.

[It's not actually an impeller, in the sense that the water flow is
entirely radial. It functions more like a water wheel on its side.
The base has a moulding inside which acts as a barrier to simple
endless rotation and the outlet is next to that barrier.]

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