Water pressure boosting, Luton: weak showers fixed, combi and unvented upgrades made possible.

Low pressure, or low flow?

People say “low pressure”, but two different things are usually going on and the fix depends on which. Pressure is the force behind the water, measured in bar; flow is how much actually arrives, measured in litres per minute. You can have decent pressure but poor flow — through a furred-up old pipe, say — or good flow but pressure that sags the moment two taps run together.

So the first thing I do on a survey is measure both at the incoming stopcock, static and under load, and count how many outlets need to run at once. That tells me whether you need more pressure, more flow, or both — and it’s the difference between fixing the problem and fitting the wrong kit.

The weak shower is the small problem

Day to day, low pressure or flow is the feeble shower, the bath that’s gone cold by the time it’s full, and the kitchen tap that dribbles when the washing machine’s running. The bigger issue is what it stops you doing.

A combi boiler needs a minimum incoming flow rate to give proper hot water — fit one on a weak supply and you’ll get lukewarm showers however good the boiler is. An unvented (mains-pressure) cylinder like a Megaflo has the same requirement: it relies on mains pressure and flow to feed the outlets, so on a poor supply it simply can’t deliver. If you’ve been quoted for a combi or unvented upgrade and someone’s mentioned the pressure, this is why — and it’s worth sorting before the new kit goes in, not after. The crossover with hot water work is covered on my boiler repair and plumbing pages.

How I boost it — properly, and within the regulations

Here’s the part that often gets skipped: you can’t simply fit a pump to the incoming main. Pumping straight off the mains can draw down the supply to your neighbours and risk pulling contaminated water back into the network, so it’s restricted under the Water Supply (Water Fittings) Regulations — the same WaterSafe rules I’m registered under. Depending on what the survey finds and what your water company allows, the compliant routes are:

• An accumulator (pressure vessel). Where the incoming flow is fine but pressure drops at peak times, a large vessel stores mains water and releases it on demand — boosting peak flow without a pump hammering the main. Often the neatest, quietest answer for a home.
• A break tank and booster set. Where flow itself is the problem, water feeds a small storage (break) cistern and a booster pump draws from that, not directly from the main — so the network is protected and you get a strong, steady supply. The right answer for bigger demands and most commercial premises.

Which route suits depends on your survey figures and what your water company allows — for most homes it’s the accumulator, with the break tank and booster set kept for bigger or commercial demand. Whatever’s fitted is sized to your measured flow and number of outlets, not guessed.

Sometimes the fix is the pipe, not a pump

Now and then the survey shows the bottleneck is the supply pipe itself — an old lead pipe, or an undersized or long run from the water meter to the house. No pump or accumulator fixes a pipe that’s too narrow, furred up or leaking underground; the real answer is to replace that supply pipe. Replacing a lead supply also takes lead out of your drinking water, which is worth doing in its own right.

That’s excavation or trenchless “moling” — pulling a new MDPE pipe through without digging the whole length — and it’s specialist groundwork I don’t take on. Where that’s the right fix, I recommend Cascadia Water, who I’ve worked alongside on projects and who do both open-cut and moling. Contact Cascadia Water →