A sump is used to collect rainwater that has been channeled through French drains or a Perforated pipe system when it's not possible to connect into the property drains because the garden slopes the wrong way or into a soakaway because the subsoil is clay.
Sump pumps are used to pump the water from the sump, into a suitable drain or area where it will disperse.
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What is a sump pit? A sump pit is a lined hole dug in your garden to collect surface water to be pumped away, essential in collecting water for some land drainage systems.
What is a sump pump?
A sump pump, is the dirty water submersible pump with a built in float switch, that pumps out the water collected in the sump and automatically cuts out when there is no water left to pump.
How to build a garden drainage sump.
Building instructions for a basic sump pit are at the bottom of this page.
Land and garden drainage sump pit information.
Sumps are the part of a garden drainage installation that collects water from the French drainage systems when the rainwater cannot be drained into the surface water system or a soakaway.
The sump pit collects the water being drained from saturated ground for pumping away. It's simply a fairly large hole dug in the garden lined with concrete or a purpose made liner, in which water collects.
The water which collects in the sump has to be pumped out from time to time and this is where the sump pump comes in as it is needed to pump the water from the garden drainage sump into the surface water drain.
Submersible sump pump information.
A sump pump, is a submersible pump with a built in float switch that automatically cuts the power to the pump when there is no water left to pump .
The pump is used for pumping out water that is being drained into a sump pit from a French drain system. The pump should always be able to pump dirty water - this means water containing grit, sand, mud and small pebbles.
It's always best to fit a submersible sump pump with a controller, normally a plastic or rubber floater that automatically switches on and off as the water rises and falls. It's also a good idea to fit a strong removable cover over the sump pit for easy access to the sump pump and to stop the kids falling into the sump.
You will also need to connect a hose to the pump to pump the rainwater into the surface drainage system. The sump pump hose can be run over the top of the lawn or garden to connect into the surface water drainage system but can be a nuisance when mowing the lawn or even a hazard for kids playing on the lawn. The pump hose is best buried under the garden or lawn.
How to build and install a sump pit for draining a waterlogged garden.
If you have a waterlogged garden or lawn, as described on my garden drainage page and can't drain the water into the surface drainage system because the garden slopes away from the house, a sump pump combined with a French drainage system is your best option. These systems are cost effective, low maintenance and activate automatically to remove the water.
Tools needed to build a sump are a spade, cement, spirit level, tape measure.digging tools
Work out the best place to dig the sump pit. This will be the lowest point of your garden or lawn and always where the surface water puddles. Remember you are connecting French drains and water will not travel uphill.
Dig the sump pit 27 to 36 inches deep and 24 inches square to allow for the concrete lining. Check the sides are smooth and free from rocks or roots and the bottom is level.
Build a wooden frame to fit inside the pit.
Pour in concrete to form the walls of the garden drainage sump, allowing at least 3 inches on all four sides. The top should be level with the lawn or a couple of inches below if you want to hide the lid under decorative gravel. Add a small strip of 1-inch wood to the top edge of the frame. When the concrete dries this will form a lip around the top of the sump pit to support the cover.
Mix the cement, following the manufactures instruction for a fairly thick mix. Now pour the concrete around the outside edges until it is flush with the lawn, then pack it down, remembering to add any additional amount needed and smooth it out.
Allow the concrete to set for a minimum of 24 hours and then remove the frame or leave it in place.
Fill the bottom 4" with at least 20m gravel. Pea gravel could block the sump pump.
Fit the sump cover.
How to connect into a Sump Pit.
When the concrete has set, drill a circle of holes and tap the center out.
Another way is to 1, Dig out the first part of the trench leaving a section of soil about 6 inches thick to hold the concrete back. 2, Pour in the concrete and let it partly set. 3, tap a section of the right size pipe through the earth and soft concrete, untill it hits the timber frame. 4, Let the whole thing set and remove the frame and section of pipe.
Make sure the pipe is set at the bottom of the trench but high enough up the sump pit to allow room for the pumpandfloat.
Fit a wire filter over the trench side of the pipe to stop gravel falling through.This can be made from chicken wire.
Do not concrete the floor of the pit, the more water that soaks away the less electricity you will use.
If you plan for more than one trench to drain into the sump, if the slopes allow, connect them into the main trench, it's easier than trying to connect them into the sump.
How to purchase a dirty water sump pump and Discharge Hose.
Measure the run, that's the distance from the sump pit to the discharge point,
Measure the rise, that's the height difference between the sump and the point the water is to be pumped too, add to the run.
Check the pump has a on off switch.
See the two sump pumps I have selected below they both meet all the criteria, I/E rise, pumping distance, dirty water and automatic on off switch.
More Technical information further down this page.
The submersible pumps featured in the drainage shop, are sump pumps I have used when installing drainage connecting to a sump pit and meet all the criteria and are available from my drainage shoppage
The 76334 pump costa around £60.00 and is Ideal for small domestic gardens pumping dirty water over a distance of 8 meters from the collection point to a drain.
I use the 69690 sump pump cost around £150.00, for larger areas and it will pump dirty water for up to 15 meters from the sump to a drain.
If the discharge hose is to be laid under the surface.
You will need a reinformed Flexible Hose and connecter that matches the pump outlet,
Hose clips and connector to join additional lengths of hose if required. The hose will need to be long enough to run from the pump to the discharge area.
A non return valve fitted to the hose, this stops the water flowing back into the sump pit, wasting electricity.
Once you have purchased the pump, I recommend contacting a specialist discharge hose supplier who will be able to advise on the correct solid hose fitted with a non return valve to fit your pump.
If the discharge hose is to be laid over the surface.
A simple "lay flat" hose can be used if the hose runs over the surface of the lawn and is not buried. and can be purchased from the drainage shop
Technical information to help select a suitable drainage sump pump.
Head and Flow Rate
The ability of a pump to pump is shown by itshead and flow rate. The head is the maximum height to which a pump can pump water. In the UK most pumps are sold with the head specified in meters or feet.
When selecting a pump you need to measure the height difference between the sump and the point the water is to be pumped too. The head of the pump must be at least 25% greater than that measured distance.
A check valve will need to be fitted as this allows water to flow up and out through the pipes. And when the pump turns off the check valve stops the water in the pipes flowing back into the sump.
The flow rate is a measure of the amount of water which can be pumped by the pump. This flow rate falls when water is pumped upwards.
Price guide for garden drainage pumps
High Flow Sump Drainage Pumps.
Submersible sump pump made of stainless steel, with a float switch, Suitable for draining a garden sump of dirty water with a 1.5" Outlet, will cost from about £560
Medium Flow Sump Drainage Pumps.
Submersible pump for sump drainage.complete with float switch. Suitable for pumping dirty water with 1.25" Outlet,will cost from about £100.
View the range of sump pumps and select one that meets all the criteria, I/E rise, pumping distance, dirty water and automatic on off switch.
If you are into DIY make sure the pump you purchase is made for the job. Make sure it switches on and off automatically and can pump water over the distance from the sump pit to the surface water drain.