Submersible pump in shallow water

[John Laird]

[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.]

[John Laird]

[I've had a thought. Sometimes you have to write a problem down and stare at it for long enough for possible solutions to spring to mind ! Anyway, all ideas welcomed.]

[Andrew Mawson]

When I had this problem two houses ago, I dug a sump and lined it with bricks laid with a honeycomb gap pattern to let the water in, and made sure that the sump was deep enough to overcome the starting problem. Worked a treat for years.

AWEM

[Ian Stirling]

Take a sturdy rubble sack or something. Take two 2m lengths of hosepipe, one 10cm. Attach one length of hosepipe by whatever means to the output. Poke the other one into the sack near the impeller. Hotmelt the three lengths of hosepipe and the mains flex together to make a nice clean blob. Tape firmly the sack round this blob.

Connect hosepipe to input tap, run it for a bit, till the water starts coming out of the short pipe. Clamp off the short pipe somehow. Submerge the input pipe. Turn on.

[hzatph]

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.

[Pete C]

Hi,

Is there a non return valve on the output of the pump? If so, does removing it allow it to start in shallower water?

Failing that, try using a water feature pump to shift the water into a container which the bigger pump can work OK in. Eg:

If the above pump is put on it's side where the intake grille is, it should be able to pump down to 1/16". Because the flow is relatively low it's unlikely to suck grit into itself.

cheers, Pete.

[John Laird]

Your middle name isn't Heath, by any chance ?

It must be early in the morning, because I've read this several times and still can't picture what you're getting at. Probably my failing !

[John Laird]

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.

[John Laird]

No, it's a very simple device. It's a bit annoying that the air space above the impeller is sufficiently large to trap air in this way. When running, I think the idea is that that water is helping to cool the motor.

Anyway, thanks for the ideas. What occurred to me was that I was, by using a bucket, creating a small sump that I then need to get out of the way once the pump is working. I think that if I cut the bottom off the bucket, and can manage to seal it sufficiently well against the floor to stop water inside flooding out of the bottom too quickly, then I should be able to:

a) Place the bucket (now a hollow cylinder) on the floor b) Drop the pump into the bucket c) Pour water into the bucket to a depth sufficient to d) Start the pump e) Lift the bucket up

The bucket is now of course trapped by the power lead and the outlet hose, but that's no big deal. c) is the tricky part - getting enough water in before it leaks back out of the bottom. I probably need to lash up some sort of seal - thinking maybe of using some split foam pipe insulation taped onto the bottom so it is easily pressed down onto an uneven surface.

[I did not mention the fun I have had trying to get water to flow through the lay-flat hose that came with the pump (I think it was laid flat with a road roller), but am hoping the pressure generated by the pump working properly will open the hose up. It's about 6m head.]

Final question - presumably I shouldn't *really* pump this water out into the surface drain on a permanent basis ?

[Ian Stirling]

What you end up with:

A sack, containing the pump, full of water. An input hose, which sucks in water, and an output hose which spews it out.

In use, the sack is under negative pressure, and collapses down onto the pump as it pumps water out of the bag. When there is no more water inside the bag, as it's all been sucked out, it starts to suck through the inlet pipe. The hotmelt is to seal the pipes/flex into a blob that can be taped round securely to make the thing airtight. Having said that, a wet/dry vac may be a much simpler solution.

[Terry]

Is it possible that you've bought the wrong pump?

I've had a problem in the cellar for years which lets the water in when the water table rises far enough. It is entirely unpredictable - no sign of water despite the amount of very heavy rain we've had recently (although it usually takes a few weeks before anything starts happening...) Strange thing is it might not happen for 2 or 3 years then it floods twice in a year! - and when it does it seems to come in rather rapidly!

I bought a "Hippo" fully submersible pump (from Argos, if memory serves me correctly) some years ago because it claimed to pump down to ~4mm (which it does) and placed it in the lowest part of the cellar, which is about halfway along . (Obviously we don't keep anything of value down there and what there is is kept above "high tide" level!)

It stays in place all year round and, to avoid paddling, the mains lead is coiled up on a hook by the cellar door. At the far end, the end of the hose is tied onto the underside of old iron coal hole cover. When water appears, the mains lead is plugged into a socket in the hallway, the cover of the coal hole is removed and the end of the hose pulled into the open and off we go!

It works perfectly: the pump never blocks (instructions are to connect hose to water tap and flush it out backwards if necessary but its never been needed) and the motor runs in oil and is rated for continuous running, wet or dry, so I just leave it running and check it occasionally until it has finished!

The important thing is that it will pump water at any depth above 4mm - so long as the input vents are covered, it works! This was a major consideration because there is a peak in the floor at the bottom of the stairs which traps ~12 - 15mm of water at the end. When the main part is pumped out, I leave the pump running and use a yard broom to drag the water up and over the top. Every time sufficient water runs down the other side to cover the pump inlet, off it goes again, so we are left with very little water at the end of the day.

(One of these days, when I get a round tuit, I'll smash down into the concrete to create a sump!)

[John Laird]

Naturally ;-) I did a fair bit of Googling and decided on one that would a) not barf at small pieces of grit and b) keep going down to a sufficiently shallow depth (8mm I think). The fact that it needs about

4-6" of water to get going was, strangely, not advertised.

It is possible to buy "puddle suckers" that are specifically aimed at doing what I am (currently) doing. However, they are fearsomely expensive to buy, and even to rent would cost as much per day as the pump I have bought which will (ultimately) do what I want.

I may give the manufacturer a ring and see if there's a helpdesk or tech support line and see if they have any clever ideas. The troubleshooting guide advises the pump may need to be tilted to assist in air removal, but this is assuming it's sitting in some depth of water anyway and has developed an air "lock".

Sounds like my house, so far as I can tell. Some of the neighbouring properties are much older and have cellars, but I have not discovered whether they have similar problems.

That is what I will end up doing, but I need to get the floor dry to work out where the water is coming in, how it flows and settles, and hence where to dig a sump hole. This is all sub-floor rather than cellar, so access is limited, awkward, and currently very wet... Not being able to get under there is currently hindering some coaxial cable running, a check on the central heating pipes to look for a small leak, and ultimately drainage of the same to fit additional TRVs and new lockshield valves.

Never fear, I have high hopes for my bottomless bucket brainwave.

Thanks for all suggestions.

[Ian Stirling]

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.

[John Laird]

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.]

[Ian Stirling]

It'd probably be easier to drill a small hole in the pump, through which you can suck out the air.

[dave northern lights]

I had the same problem in the previous house, I also bought a Hypo pump, I put a small sump in the corner of the cellar that was easiest to pass the output hose throught the wall to an outside drain. The sum was only 8" by 12" and a depth of 12", I didn't even line it just dug it down into the clay. Float switch I wired close to the body of the pump to be able to work in a confined sump.

It worked perfectly for 2 years, however it was always going off every

5 mins which I thought was strange even in dry periods, therefore phoned water company to say I thought they had a problem. They came and had a look, put a camera down the drains outside and found there was a hole, which they fixed. Pump still going off every 5 mins! Called them again. Old guy came out see the sump and the pump going, went outside to his van to get his listening stick, placed it on stop valve to neighbours property and said they had a leak! Cost them a chunk of money to have it dug up and fixed but it cured my problem.

John Laird wrote:

[John Laird]

This worked, as it happens, once I had found a sufficiently flat area of the floor onto which I could get a decent seal. I duck-taped a length of 15mm pipe insulation round the bottom of the bucket, but it wasn't sufficiently compressible to work on rough areas.

It's going to take a few attempts to get enough water out (assisted by my trusty Vax wet-n-dry vacuum) for me to get underneath and have a good look around. I think I may have to try and dam off the various areas of the sub-floor with some sand in order to be sure I know where the water is coming in - it's rather mobile, as one might expect !