Sewage pumps are used when gravity drainage is not viable. In most situations wastewater is designed and piped to flow downhill on its own, to the nearest manhole, which in turn flows downhill to the main sewer. However, if the toilet, shower or sink sits lower than the point it needs to discharge to, you need a pump to move it.
You would also require a pump where the “fall” or gradient, on a pipe is not sufficient for gravity flow.
Without enough gradient, the flow will be insufficient, meaning blockages form, and you’ll have continued problems. A example perhaps would be a garden office at the bottom of the garden. You might install a toilet and a sink, only to discover there is not enough fall to reach the main sewer, and thus, a pump would be required.
Typical UK Gravity Drainage Falls (Building Regs and BS EN 12056)
• 100mm (110mm) foul drainage:
Recommended gradient is 1:40
Minimum acceptable gradient is usually 1:80 if flows are adequate
Once a sewage pump is doing the work, the discharge pipework becomes pressurised, so you no longer need to maintain a specific fall. Instead, you follow the pump manufacturer’s guidance on the maximum vertical lift, the horizontal run, the pipe diameter and the number of bends allowed. This is where understanding pump curves matters, as you need to know both the flow and the head the pump will deliver.
Tank size and flow rate must also match the number of toilets and users. A system serving several properties will need a far larger tank than something serving a single washroom. To avoid issues later it is recommended that a consulting drainage engineer size and specify the tank and pump at the drainage design stage.
If the work involves a new drainage connection, you may also need a Section 106 agreement. Section 106 of the Water Industry Act 1991 gives you the right to connect foul or surface water drainage into the public sewer. Again, this is something a consulting drainage engineer should deal with for you.
Sewage pumps are usually automatic, either with an attached float switch or designed to work with a float inside a chamber. A sewage pump should always be automatic, so you do not end up manually monitoring tank levels. The pump will start when the chamber fills and stop once the liquid drops to the correct level.
Unlike puddle pumps, sewage pumps sit on a stand and have large openings that allow solids to pass through. They cannot pump down to low water levels because that would impact their solids handling ability. They must be set inside a chamber which collects liquid and solids, and when the level rises in the tank, the pump activates. Most sewage pumps use pendant float switches because other types, such as tube floats or sensors, are more likely to snag or clog.
The diagram below compares the openings of low level pumps, with sewage pumps.
Below are three sewage pump options which cover a range of needs. At the smaller end is the APP SV 150 Auto, which delivers 170 litres per minute at a head of 5.7 metres. At the top end is the Speroni Cutty with up to 400 litres per minute and an impressive 27 metre head. In the middle is a packaged pump station which gives you everything you need for a garden room or similar setup.
Perfect for sewage and draining, the SV series of submersible pumps are manufactured by APP Pumps, and are a great range of submersible pumps that come with cast iron pump casings, vortex impellers and 304 stainless steel motor frames.
Head: 5.7m
Flow rate: 170 litres/min
The Foul Pro system uses the EVAK Hippo 100 Sewage Pump, providing increased flow and head performance compared with the standard model. This pump delivers a flow rate of up to 480 litres per minute and a maximum head of 11 metres, making it suitable for larger foul drainage systems or sites with higher discharge lifts.
The CUTTY series grinder pumps are of cast iron construction.
They are used in sewage stations and for servicing individual, or groups, of houses where drainage by gravity is not possible. They are ideally suited to applications where effluent is required to be pumped over a long distance, through a small bore pipe.
Head: 17 - 27m (model dependent)
Flow rate: 300 - 400 litres/min (model dependent)
Sewage pumps are used when gravity drainage is not viable. In most situations wastewater is designed and piped to flow downhill on its own, to the nearest manhole, which in turn flows downhill to the main sewer. However, if the...
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For applications requiring serious water-moving capability, the APP HD-15 is a standout solution.
