[I posted about problems with some standing water in a sub-floor a few
weeks ago. It seems most likely this is simply related to a high water
table.]

I now have a small submersible sump pump, which will be installed in
due course, once I have decided where the water is coming in and hence
where to dig a hole. (Hopefully in a convenient spot, and not
necessarily at the lowest point anywhere, which may be harder to get
to.)

I bought one which will deal with small particles, so as not to clog
with the silt coming off the concrete, and which claims to pump down to
8mm minimum depth, as I was hoping to use it to clear most of the water
that has gathered at the moment. (I imagine it may take me a few
iterations of emptying and monitoring to work out the water ingress
points and best place for a sump.)

But... the pump won't get "started" in the 2" deep area of the puddle
that I can easily get to. Experiments in a deep sink would suggest
another couple of inches is required to stop the impeller simply
spinning around mostly in air and get the air pocket above it forced
out. The water under the floor may be slightly deeper elsewhere, but
I'd need a wet suit to persuade me to crawl about in 2' of headroom
trailing a pump and torch and hose and looking for a deep spot.

A challenge for the lateral thinkers of uk.d-i-y then - how to get the
pump started properly ? I have tried immersing it in a bucket and
running it there briefly, but I haven't been able to pull the pump out
of the bucket and sit it on the floor without too much water running
out and air getting in above the impeller again. I thought of "lining"
the bucket with a plastic bag and then lifting the bag and pump out
into the sub-floor and then letting the bag down while starting the
pump, but am worried the pump might contrive to suck the bag in. I
doubt I could dig away at the concrete under the access hatch to make a
deeper hole as there is very limited room and it is no doubt a few
inches thick anyway.

TIA.

[PS Yes I am aware the pump should only be run for short periods when
not fully submerged, but a few runs of 10 minutes each should get rid
of enough water for me to proceed with investigations.]

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