Skip to content
Description
When the mains itself is tired, everything downstream feels it. The water company’s answer is usually a shrug — the supply meets the minimum, and the minimum isn’t much.
The worst of it is that when pressures are at their lowest, you will be competing for pressure with your neighbours. As long as there is enough water to run a shower, no matter how low the pressure, a SP21S Mains Pressure will increase the pressure high enough for a shower on the second floor. Whilst you can enjoy a shower when you want a shower you want, your neighbours, unless they also fit a SP21S – will not.
The SP21S is legal and fair because it takes less than the legal maximum and it does not depressurise the main. You are only taking your fair and legal share of the water available.
Whilst you may have been told whole-house mains pressure can’t be fixed from inside the house, it can — from under your kitchen sink.
The SP21S for mains pressure is two WRAS-approved booster pumps fitted in series, tucked under the kitchen sink on the incoming supply. Working together they support up to 8 litres a minute to a struggling main — felt at every outlet the supply feeds. In everyday terms: the kettle fills while you fetch the mug, and the shower stops noticing the washing machine. The pumps start automatically when water flows and stop when it doesn’t, all on one 3-amp transformer plugged into a normal socket.
It’s a simple DIY installation: cut the pipe, fit the pumps, plug in. And because the pumps are WRAS approved and compliant with UK Water Byelaws, fitting them to the incoming mains is fully legal.
Q: Why under the kitchen sink?
A: The kitchen sink usually sits close to where the mains supply enters the house, with easy access and a socket nearby — so the pumps boost the supply before it splits off around the house.
Q: Will it help my combi boiler too?
A: If your boiler cuts out from low mains pressure, yes — this is the same fix but it works better if you boost just the combi boiler feed. See the SP21S combi boiler page for the boiler-specific detail.
Q: My mains pressure is extremely low. Should I still buy?
A: Call us first on 01928 620 099 — with very low mains we’d rather check your setup than have you buy twice.
Â