Sewage Pumps

Sewage pumps are used across a wide range of applications:

• Basement bathrooms below the level of the street sewer, particularly common in London and Victorian terraces
• Garden offices, annexes and outbuildings where the fall to the main sewer is insufficient
• Packaged sewage pump stations for new builds, conversions and developments
• Commercial and industrial foul water systems including sewage treatment works
• Pump stations serving multiple properties on housing estates
• Agricultural and rural foul drainage where properties are off the main sewer

The preferred option on any build is always gravity drainage, which directs sewage to flow down the natural slope of the land. When that isn't possible, a sewage pump is required.

Because sewage pumps have to handle liquids containing solids, they are built differently from standard water pumps. There are three main types:

1. Vortex Impeller Pumps

Vortex pumps are designed to allow unimpeded passage of solids. The impeller creates a whirlpool effect that moves solids through the pump without them ever touching the blades. Pumps like the EVAK Hippo 50, Hippo 75, Hippo 100 and Hippo 200 have a free passage of up to 50mm. In the product video you'll see them pumping table tennis balls through without clogging, or damaging the balls. Vortex pumps are the default choice for most domestic and light commercial sewage applications.

2. Cutter Pumps

Cutter pumps, like the APP DSPK Cutter Sewage Pump, are fitted with a cutting blade that chops solids into smaller pieces before pumping. They are ideal for fibrous materials, wet wipes and tough waste that would otherwise clog a standard pump. Cutter pumps are a strong choice where the downstream pipework is narrow or the pump is serving a public-facing site (pubs, offices, holiday lets) where non-flushables frequently enter the system.

3. Grinder Pumps

Grinder pumps, like the Speroni Cutty, use a grinding mechanism to reduce solids to a slurry, allowing the sewage to be pumped through small-bore pipework over long distances. They are commonly specified for sewage pumping stations where the discharge main is smaller than standard, or where long pipe runs make a grinder the most efficient option.

A sewage pump sits on a stand inside a chamber and has large inlet openings to allow solids to pass through. This is the critical difference between a sewage pump and a puddle pump or drainage pump. A sewage pump cannot pump down to low water levels, because the openings required for solids handling would simply pass air once the level dropped.

Most sewage pumps use pendant float switches rather than tube floats or sensors, because pendant floats are far less likely to snag or clog in foul water.

Sewage pumps are designed to run in bursts (on-off cycles) rather than continuously. When the chamber fills, the float switch triggers the pump, and it runs until the level drops. This is why correct sizing matters: an oversized pump will short-cycle, which shortens the life of the motor and float.

For installations that need a complete, ready-to-install solution (basement bathrooms, ground floor extensions, or any site where foul water needs collecting and pumping away), we supply Packaged Pump Stations, with options built around the Hippo and FEKA pump families.

Each packaged pump station is supplied with the chamber, pump, internal pipework, non-return valve and float switch, ready to install. We continue to expand this range.

• Head Height: The vertical distance the pump has to lift the water, plus friction losses along the pipe run. The first question on any sewage pump selection.
• Flow Rate: Needs to match the number of bathrooms or users served. A pump that's too small will short-cycle as the chamber refills faster than it empties.
• Solids Handling: 50mm free passage is the standard for domestic foul water. Cutter or grinder pumps should be specified where wet wipes, fibrous waste or small-bore discharge pipework are involved.
• Voltage: 230V single-phase for domestic, 400V three-phase for larger commercial pumps, 110V for site use.
• Automatic or Manual: Sewage pumps should nearly always be automatic (float-switched), so the tank is managed without operator intervention. It can also be common for a manual pump to be installed, and activated by a separate float switching mechanism.
• Chamber Size: The pump must be matched to the chamber size which should be large enough to allow the pump to run in sensible cycles, neither starving nor short-cycling.

For deeper reading on head, flow and system design, see our Ultimate Guide to Sewage Pumps or use the Water Pump Performance Calculator to work out pipe friction losses.

Sizing and Building Regulations. Foul drainage is regulated work. In England, Approved Document H is the guidance used to show compliance, and it points to units that meet BS EN 12050, with systems designed to BS EN 12056. The key sizing rule is that a pumped chamber should hold a full day's inflow in case of a fault, taken as 150 litres per person per day for domestic use. That is why a foul installation is sized around the number of people it serves, not just the pump's flow rate. We explain this in plain terms in Sewage Pumps and Building Regulations: Approved Document H Explained.

All sewage pumps can become "ragged" over time, particularly where wet wipes, sanitary products or other non-flushables have entered the system. De-ragging involves isolating the pump, lifting it from the chamber and clearing the impeller and inlet.

To minimise de-ragging, only flush toilet paper and organic waste down any toilet connected to a sewage pump. Wet wipes, even those labelled "flushable," are the single biggest cause of sewage pump callouts. If the site is public-facing or occupied by tenants, specifying a cutter pump or grinder pump from the outset will dramatically reduce maintenance calls.

Every pump comes with a performance curve, and it is the single most useful number on the data sheet. The vertical axis is head (the total height the pump works against, including friction losses), and the horizontal axis is flow (how much water it moves). The two trade off against each other: the more height you ask for, the less flow you get.

The point that matters is your duty point, where your installation's total head meets the curve. That, not the headline "maximum flow" figure, tells you what a pump will actually deliver. The rule we use is the middle-third rule: specify a pump so its duty point sits in the middle third of its curve, where it runs efficiently and lasts longest. It is why a bigger pump is not the safe option, an oversized pump runs off the end of its curve, wastes energy and wears out faster.

For the full walk-through, including a car-engine analogy that makes it click, read How to Read a Pump Curve and Choose the Right Pump.

We've spent years sourcing and testing sewage pumps across our hire, supply and consultancy work, and we only stock pumps we'd specify on our own drainage projects. Every pump in the range is backed by a manufacturer warranty (many with 2 or 3 years), supported by our UK helpdesk on 0115 987 0358, and held in stock at our Nottingham warehouse for next-day delivery across the UK.

If you're unsure which sewage pump is right for your application, call the helpdesk. We'd rather not sell you the wrong pump.

We're the pump supply arm of Flood Protection Solutions Ltd, trading since 2012. Our sister company, also part of the FPS Group®, is FPS Environmental Ltd, who offer foul drainage design and consultancy for new builds, conversions, developments and pump station design, from initial concept and planning through to detailed system design.