Most pumping mistakes are surprisingly easy to avoid once you understand what is really going on. The truth is, pumps follow the same basic rules of physics and engineering as plenty of other bits of kit we use every day. The difference is that most people have not needed a water pump before. Or, if they have, it has usually been running quietly in the background, doing its job without anyone noticing, until something goes wrong.
This is not a technical guide full of jargon. It is simply a collection of real-world lessons, the kind that come from experience, which can save you time, money and frustration.
1. Choosing a pump that is too big or too small
Too big
A lot of people assume a bigger pump must be better, the more speed and power the better, but this is not the case with water pumps. We want a well matched and suitably specified option.
If the pump is too powerful, it will either end up running dry if it is a manual pump, or, if automatic, keep switching itself on and off quickly because it is emptying a chamber too quickly. This constant starting and stopping (often called short cycling) wears the pump out much faster than if it were to run for extended periods, with the water flow cooling the motor. We can relate this to town driving, stop-start, causing more wear on a car than cruising along a motorway in a high gear at low revs.
You also do not want to overload the area you are discharging to.
Given pumps are mechanical items, we will again relate it to cars. You will not get there any faster by accelerating rapidly, nearly hitting the car in front, then jamming your brakes on. Better to stay trundling along at a safe distance with limited wear on the engine or brakes. The same is true for water pumps and the associated flow rate.
If you choose a swimming pool pump that is too large, you can also end up with an electricity bill higher than needed, and even overload the pool's filtration system.
Too small
If the pump is too small, you can either end up with a problem forming (imagine if a sewage pump was undersized and could not keep up with the inflow), or, if a pump was being used in a flood and could not keep up with the flow rate of water entering, the flood depth would increase. Alongside this, you must also ensure you have enough power to pump the distance you are requiring the pump to discharge the water to.
The key is finding the right balance. Match the pump to the job: the height, the distance, and the amount of water you actually need to move.
This is why understanding the pump performance curve is important, which you can read about in Pump Curves Explained.
2. Forgetting about head height and friction loss
This is one that catches a lot of people out. Head height is not just about how high the water has to go. It is everything that gets in the way: the bends, the hose, and the friction as the water moves through the pipework.
As a rough guide, every 10 metres of hose lying flat is roughly the same as pumping one metre upwards. So if you have a long run of hose going across a garden or up a slope, that resistance adds up quickly.
If you ignore it, your pump might seem weak when it is working exactly as it should. It is having to overcome physics.
3. Using the wrong hose
Over the years, we have seen a number of setups where the hose or pipework is the problem, not the pump.
Garden hoses, for example, are only about 13mm wide, so you would lose most of your flow before the water even gets out of the end. For most jobs, especially where floods are involved, you are better off using proper suction delivery hose or layflat hose. We compare them in layflat hose vs suction delivery hose.
Suction delivery hose does not kink and keeps the flow rate strong. Layflat hose is easier to roll up and store. Which one you use depends on the job, but a garden hose usually is not the answer.
If you have a fixed installation, it is also important to consider the requirements before specifying the pump or pipework, otherwise you could end up with the incorrect pipe size or connections for the required job. Where there are specific requirements, such as a pumped drainage system, a consulting engineer should always be involved to determine the specifics first. It can feel frustrating to pay for expertise up front, but it will be worth it.
4. Running the pump dry
It is an easy mistake to make. You start the pump, the water drops, and before you know it, it is running dry. Most pumps rely on water to keep the motor cool. Without it, they can overheat or damage the seals in minutes. Automatic pumps are less exposed to this, but it can still occur if the float switch gets snagged.
Some pumps, like the Tsurumi LSC1.4S puddle pump, are designed for really shallow water and can handle it for extended periods, but most cannot. Always check before switching one on: if it needs water, make sure there is enough for it to function.
5. Forgetting maintenance
Pumps do not need much looking after, but they do need some.
Give yours a quick run every now and then, especially before bad weather. Check that the float switch moves freely and that nothing is blocking the inlet. It takes five minutes and can stop a lot of problems later on.
Simple things help. For instance, if you are using a pump to drain a hot tub or swimming pool that are chlorinated, flush the pump through afterwards with clean water.
6. Not thinking about where the water is going
This sounds obvious, but it is one that is easy to miss. Before you start pumping, make sure the water actually has somewhere to go: a drain, ditch, soakaway or safe discharge point.
Without considering this early on, you cannot determine what length of hose you would need, which helps determine what pump may suit your requirements.
To conclude
A well-chosen pump should last for years if it is used properly. Take the time to get the setup right, the right pump, the right hose and the right placement, and it will quietly do its job without much fuss. If you are purchasing a replacement pump, one of our first questions would always be how long the old one lasted. While there are undoubtedly some poorly made pumps with limited lifespans available from certain online stores, if a pump has failed prematurely there is often a factor driving this, and replaced like for like, the same failure could occur again.
These are the general versions of the issues we see specifically on sump installations, which we cover in avoiding common sump pump mistakes, and the engineering principles behind them in the engineering behind a reliable pump installation.
If you are unsure which setup is best, just ask. At floodandwaterpumps.co.uk we are always happy to help, and the Pump Finder is a good place to start. Sometimes a quick chat saves a lot of time and money later on. And if the requirements are specific, we can pass you to a consulting engineer at our sister company FPS Environmental Ltd, who may advise a site visit or other calculations as necessary.
