When a water company builds a pumping station to move wastewater away from a street or village, it works to a national specification rather than guesswork. One of these is WIS 4-04-02, a Water Industry Specification covering pumping stations that serve more than one property. Most of it is detail you would never need at home, but the principles behind it explain why pumps fail, and they apply just as much to a single pump in a cellar or garden as to one serving a hundred homes.
Here are the ones worth knowing, and what they mean for your pump.
1. A pump that keeps switching on and off is wearing itself out
Pumping stations are set up so the pump does not keep starting repeatedly. Every start draws a surge of current and heats the motor, and frequent starting shortens its life. So if your pump switches on, runs for a few seconds, switches off, then does the same again moments later, treat it as a fault to correct rather than a quirk. This is called short cycling, and it is one of the most common reasons a pump fails early. It is usually one of two things:
- The chamber the pump sits in is too small, so it fills and empties in seconds. The fix is a larger chamber, or adjusting the float switch (the floating on/off trigger) so the water has more room to rise and fall between the pump cutting in and out.
- The water just pumped out is draining back down the pipe and refilling the chamber, which restarts the pump. The cure is a non-return valve (a one-way valve) on the outlet pipe, which lets water out but not back. You will find them in our pump valves section.
2. A pump needs water around it to survive
In a pumping station, the controls keep enough water over the pump before it switches off. A submersible pump uses the surrounding water to keep its motor cool, so if the level drops too far it begins drawing in air and the motor loses its cooling and overheats.
The practical lesson is to avoid running a pump on in an almost empty sump, and not to set it to switch off at a level that leaves it sitting in air.
If the aim is to clear water down to floor level, use a puddle pump, which is designed to work down to the last few millimetres, rather than a standard drainage pump.
3. For anything critical, do not rely on a single pump
A pumping station that protects something important is built with two pumps: a duty pump that does the work, and a standby pump that takes over automatically if the first fails or cannot keep up. An alarm warns well before the water reaches a damaging level.
The same applies to you. If a pump is the only thing protecting a finished basement, a server room or stock you cannot replace, a single pump is one point of failure: if it fails or the power cuts out, you have nothing. Consider a second pump set to start at a higher level, and a high-level alarm. For higher-risk sites, our Engineering Review Service can specify the right level of protection.
4. The right size beats the biggest size
Pumping stations are sized to the job, not simply made as powerful as possible. An oversized pump can empty the chamber so quickly that it short cycles, it can cost more to run, and on dirty water an oversized pipe lets the flow slow down enough for solids to settle and block it.
Getting the size right is the most valuable decision. Our Pump Finder is a good starting point, or tell us what you are pumping, where from and where to, and we will match the pump to the job. You can also browse our sump pumps and packaged pump stations, or call 0115 987 0358.
Switching on and off too often, running dry, having no backup, and choosing on size alone account for most pumps that fail early, at every scale. Avoid them and a well chosen pump will run reliably for years.
Frequently asked questions
Why does my pump keep switching on and off?
This is short cycling. It usually means the chamber is too small, the float switch has too little travel, or there is no non-return valve on the outlet, so pumped water drains back and restarts the pump. Each rapid start heats and wears the motor, so it is worth correcting.
Why has my pump failed so soon?
The two most common causes are starting too frequently and running with too little water around it, both of which overheat the motor. A correctly sized chamber, a non-return valve on the outlet, and never running the pump dry all extend its life.
Do I need a backup pump?
If the pump protects something you cannot afford to lose, yes. A second pump set to start at a higher level, or a battery-powered pump for power cuts, removes the single point of failure. A high-level alarm provides early warning.
Is a bigger pump always better?
No. An oversized pump can short cycle, cost more to run, and on dirty water oversized pipework can let solids settle and block. Matching the pump to the job is what matters.
