Which homes they're for
Power showers and shower pumps are designed for gravity-fed (vented) hot water systems: a cold water tank in the loft feeding a hot water cylinder, usually in an airing cupboard. In these systems, pressure at the shower depends on the height of the tank above the shower head, which is often not much.
They are not suitable for combi boilers, unvented cylinders or anything connected directly to the mains. Water regulations restrict pumping from the mains supply, and doing so can starve the supply to other homes.
Power shower or separate pump?
A power shower is an all-in-one unit: a mixer valve with a built-in pump, mounted on the wall in the shower. It's a simple way to boost a single shower.
A separate shower pump is installed near the cylinder, often in the airing cupboard or loft, and boosts the hot and cold supplies to a mixer shower. Some pumps can supply more than one outlet, such as a bath tap as well as a shower.
| Power shower | Separate pump | |
|---|---|---|
| Where it goes | On the wall in the shower | Near the cylinder or in the loft |
| Outlets | One shower | One or several |
| Choice of shower | Limited to power shower models | Most mixer showers |
| Noise | Pump is in the bathroom | Pump is away from the bathroom |
Power shower or separate pump – a quick comparison
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Positive and negative head
If water already flows to the shower by gravity, the pump is 'positive head'. If the shower is level with or above the tank – common in loft conversions – or the flow is too weak to trigger a positive-head pump, you need a 'negative head' pump. Choosing the wrong type is one of the main reasons pumps fail early or don't switch on reliably.
Getting the installation right
A good installation makes the difference between a pump you barely hear and one that rattles the house. Plumbers mount pumps on a solid base with anti-vibration feet, use flexible hoses, and connect to the cylinder in a way that prevents air being drawn into the pump. The cold water tank needs to be large enough to supply the extra flow, and the cylinder needs to keep up with demand.
- Check your system is tank-fed before buying anything
- Make sure the cold water tank is big enough for the pump's flow
- Use a dedicated connection on the cylinder where recommended
- Fit isolating valves so the pump can be serviced
- Allow access for future maintenance
