November 12th, 2020 by Sarah Miles

A submersible pump is an excellent tool for draining various bodies of water, including pools and hot tubs, but is probably best known for getting rid of floodwater. However, did you realise that submersible pumps can also be used as a preventative measure to defend against flooding?

If you live in a flood-prone area you may well be aware of the devastation that a flood can bring, and you will also know that it can be very hard to get home insurance – especially if you have previously had to claim for flood damage. A submersible pump can’t necessarily prevent a flood in your home at ground level but it can ward off rising water below ground, such as in your cellar or basement.

How to use a submersible pump in your cellar to prevent flooding

Water levels can rise for several reasons: heavy rainfall, burst pipes, water leaks etc. Water will always find the lowest ingress point and that can often lead to flooded cellars and basements. If you don’t go down there very often, you may not even realise straight away that there is a problem and it may then be too late to rescue your possessions plus it can create a damp problem. Many use their cellars as a laundry room and a faulty washing machine or plumbing can also flood the area.

One preventative measure can be to tank the space out, making it watertight, but this can be quite expensive (and won’t protect against floods that originate within the space such as a washing machine flood). A submersible pump is a much cheaper way of proactively safeguarding against water levels rising.

First, you will need to create a sump pit to collect any flood water at a lower point to the rest of the cellar. Remember that submersible pumps can only work when submerged in water so simply placing one on the cellar floor would require the whole cellar to flood to a certain height for the unit to start pumping. The sump pit should be at least 22 inches deep with a diameter of 18-24 inches, but make sure it will comfortably accommodate your choice of pump.

Place the pump in the pit, connect to a power source, and turn on. You can then safely leave it. If water enters the cellar it will, as previously stated, find the lowest point – the sump pit. Once it rises around the pump to a sufficient level, it will automatically start pumping. Thus, heading the problem off before it really starts and without you having to do anything.

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Some things to note

Now, there are a few things you need to take into consideration. Firstly, you will need to make sure that your pump of choice is an automatic one so that it will start pumping on submersion. It is also advisable to use a pump that is suitable for dirty water as flood water could just as easily be sewage as clean water from a burst pipe.

You will also need a safe place to pump the water away to. This needs to direct the water away from the house using a hose where it won’t cause issues elsewhere.

Could it run the pump dry?

Submersible pumps have to be submerged to run and running any pump dry will damage it. However, submersible pumps with a float switch have a built-in safeguard against this problem as this will turn the pump off when water levels drop too low for the unit.

Check periodically

While this is an automatic solution that doesn’t require you to be on hand to start things running, bear in mind that the majority of submersible pumps will not drain all water away as they can’t run dry. It’s therefore worth just checking every so often to see whether low levels of water have accumulated in the bottom of the sump pit and drying it out so that the pump doesn’t remain standing in water for long periods.

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Using a submersible pump outside

The same principle can be used outside in the garden in areas that tend to flood, as long as you have access to a power source. Again, create a sump pit in the ground and direct water away safely. It can be useful to use during building works to keep foundation trenches from becoming waterlogged.