Pool pump conundrum

[NDA]

I'm draining a swimming pool at the moment to be retiled, turned skimmer valve off and set to waste...

All fine until it gets to about a foot down and then the pump runs dry.... very odd.

I've taken the pump apart and cleaned the impeller, all is working as it should be - but it doesn't seem to pull water.

Any experts here?

I wondered if the valve handle was knackered - maybe pulling in air from somewhere?

[7 Sevens]

Never had a problem with Dad's one when emptying it.

Have you tried to back fill the pump with a hosepip should you have pulled some air when inspecting it? I guess you have lost all pressure now?

[NDA]

I've been charging/priming the pump every time - filling the strainer basket with water. But it just empties and runs dry....

[andy43]

I've been desperately trying to think of a Michael Barrymore joke, but can't think of anything appropriate relating to sucking a pool dry.
Sorry

[NDA]

Maybe there's a fag stuck in the filter?

[andy43]

NDA said:

Maybe there's a fag stuck in the filter?

Damn. I knew there was a joke there somewhere.

[jeff m]

I would guess that your valve that shuts off the skimmer is worn.
When you start off with a full pool it's ok but as the pool gets lower the pump has to pull harder to raise the water hence pulls air from the skimmer.

I assume you are repriming in the pump basket ??

Try reprimng, then get a hose and fill the skimmer upto the brim. Start pump then open the hose again just fast enough to prevent the skimmer emptying but not fast enough to flow back into the pool.

Whether that will work depends on how badly your valve is leaking.

OR.....get a winter "bung" and plugger your skimmer. (much easier why didn't I think of that before typing)

[NDA]

I had thought of trying the bung in there - but didn't do it.

I'll give it a go.....

The valves are ancient iron or steel things - but they feel very solid. However I think your diagnosis must be correct. I replaced the gasket in the multiport earlier in the day but no joy with the problem...

Hmmm. A bung it is!

[jeff m]

Using your pool pump to empty the pool puts quite a strain on it as it has to pull quite a head of water as it gets lower and lower (assume 8 foot pool)
Most pros don't use the pool pump to empty.
You may still have a problem as it gets down to the last couple of feet, you might need to rent a 4" pump to pull the last bit.

They shift 20,000 galls in a couple of hours.

good luck

[NDA]

I've abandoned the pool pump and used a submersible pump - pool now drained, people now attacking it with hammers....

[NDA]

As an aside, when switched to waste there was water coming out of the inlet (in the pool). I'm not sure I understand why this would be....

[jeff m]

NDA said:

As an aside, when switched to waste there was water coming out of the inlet (in the pool). I'm not sure I understand why this would be....

A typical pool pump is 1 1/2 or 2 hp impeller type and only moves water through the filter, it only has to pull a head of water at start up. Once it's running the piping assists in the flow back to the pool water level.

Once that pool level gets down a bit (like below the returns) the pressures on the valves and pump rise quite a lot.

I assume you have a rotary valve.....Unless it leaks externally I would not worry.

I bet you are glad Dad is picking up the tab for the re-tiling