Low Water Pressure in the House: Causes and Solutions

Low water pressure affects everything from your morning shower to how long the washing machine takes to fill. The good news is that one of the most common causes takes thirty seconds to rule out.

Whether the problem affects the whole house or just one tap or shower, the pattern tells you a lot about the cause. This guide covers the signs, the eight common causes, what you can try yourself, and the professional fixes when that is not enough.

Signs your water pressure is low

It is not always obvious whether pressure is genuinely low or you have just got used to it. These are the telltale signs:

• Weak showers. A trickle rather than a spray, and rinsing shampoo out takes forever. Mixer showers are particularly affected.
• Slow-filling taps. The kettle, the washing up bowl and the bath all take ages, and the water comes out in a weak stream.
• Toilet cisterns. The toilet takes several minutes to refill after flushing because the float valve is struggling.
• Boiler problems. A combi struggles to heat water properly or shows error codes, because low flow affects how it performs.
• Appliance problems. The washing machine or dishwasher takes much longer to fill, and may show an error code or refuse to run.
• Two outlets at once. When someone uses water elsewhere in the house, your shower or tap drops away dramatically.

Start here: check your stopcock

A partially closed main stopcock accounts for a surprising share of low pressure calls. It happens after plumbing work, or when someone closes it and does not reopen it fully.

Find it, usually under the kitchen sink, and turn it anticlockwise as far as it will go. If your pressure improves, you are done. If it is not under the sink, the other usual places are a downstairs toilet or near the front door.

The eight common causes

1. Partially closed stop tap. Very common after plumbing work. Affects the whole house. Free to fix.

2. Blocked or scaled pipes. Very common in hard water areas, and most of West Sussex is hard water. Usually affects hot more than cold, and it gets worse gradually over years. The fix is descaling, or replacing the worst pipework in severe cases, with a water softener to stop it coming back.

3. Water leaks. Common in older properties. Often comes with damp patches or an unexplained rise in your water bill. Needs finding and fixing, since leaks never improve on their own. Left alone they get worse and cause water damage as well.

4. A faulty pressure reducing valve. Less common, and only relevant if your property has one fitted. Tends to come on suddenly. It needs adjusting or replacing by a qualified plumber.

5. Old corroded pipework. Common in properties over forty years old with original pipes. Gradual and progressive. The fix is replacement, which is major work but transforms the result.

6. Shared supply problems. Common in flats and terraces on a shared supply pipe. Noticeably worse at peak times, usually mornings and evenings. The answer is usually a pump or a separate, larger supply pipe from the water main.

7. Genuinely low mains pressure. More likely in rural areas or at elevation. Caterham, sitting high on the North Downs, is a local example. If the neighbours have it too, it is the mains. If it has always been low, a pump system or an accumulator is the usual fix, and it is worth raising with your water company as well.

8. Clogged aerators and showerheads. Very common, and the easiest thing on this list to fix yourself. The giveaway is that only one tap or shower is affected.

The causes at a glance

Cause	What it affects	Usual fix
Stopcock not fully open	Whole house	Open it fully
Scale in the pipes	Gradual, hot more than cold	Descale, softener, pipe replacement if severe
Leak	Whole house, often with damp or high bills	Leak detection and repair
Faulty pressure reducing valve	Whole house, sudden	Adjust or replace
Old corroded pipes	Whole house, worsening over years	Repipe
Shared supply	Whole house, worst at peak times	Pump or separate supply
Low mains pressure	Always low, neighbours too	Pump, accumulator, water company
Clogged aerator or showerhead	One tap or shower	Clean or replace

What you can try yourself

Check the main stopcock. Fully open, turned anticlockwise as far as it goes.

Clean the tap aerators. Unscrew the mesh filter at the tap spout, soak it in vinegar for an hour, rinse and refit. Do every affected tap, not just the worst one.

Clean the showerheads. Remove, soak in white vinegar overnight, scrub the holes with an old toothbrush, rinse and refit.

Check the isolation valves. Small valves under taps and toilets. Make sure they are fully open.

Ask the neighbours. If they have the same problem it is a mains supply issue and your water company needs to know. Their contact details are on your water bill.

Look for signs of a leak. Damp patches inside or outside the property, wet ground along the line of the supply pipe, and any drips on visible pipework.

Run the water meter test. Turn off every tap and appliance, note the meter reading, use no water for two hours, then read it again. If it has moved, you have a leak somewhere.

Professional fixes

Pump installation boosts pressure throughout the property. The right answer for a poor mains supply or a shared pipe. It means several taps and showers can run at once without the flow collapsing. Pumps that draw straight from the mains are restricted under the water regulations, so a whole-house system often draws from a storage tank instead, and it needs designing properly rather than simply fitting.

An accumulator tank stores pressurised water and smooths out fluctuation. Good where pressure varies through the day. It gives more consistent pressure, helps a combi boiler perform, and is a relatively affordable option.

Repiping replaces old, corroded or undersized pipework. Major work, but it permanently solves the problem and eliminates future corrosion. Modern, larger pipework also adds value to the property.

A water softener prevents future scale buildup in hard water areas, and protects appliances at the same time. It also means less cleaning, and many people find the water kinder to skin and hair.

Leak detection and repair finds hidden leaks without lifting every floor first. Fixing the leak stops the water waste, prevents damage to the property, brings the water bill down and restores the pressure. If you suspect one, our leak detection service is the place to start.

For the pump, accumulator and pipework options, we assess the supply first and recommend the most cost-effective route as part of our plumbing repairs service.

Specific situations

Low pressure upstairs only. Usually a gravity-fed system running low, or undersized pipework to the upper floor. Blocked pipes to the upstairs are another cause. The fixes are a pump, larger pipework, or converting to a mains-pressure system.

Low hot water pressure only. Often a scaled heat exchanger in a combi, or a blocked hot water circuit. A service or a descale usually sorts it. With a hot water cylinder fed from a tank in the loft, the hot water pressure depends on the height of that tank, so it is naturally lower than mains pressure. A shower pump or an unvented cylinder is the usual answer, and an unvented cylinder must be fitted by a G3 qualified installer.

One shower affected. Almost always the showerhead, the hose or the valve rather than the house supply. Clean or replace the head, replace the hose, or look at the valve. If it is a low-pressure shower on a gravity-fed system, a pump, a power shower or an electric shower is the fix.

A new build or extension. Frequently undersized supply pipes, or a mains supply that was adequate before the property got bigger. Poor plumbing design plays a part too. The usual fixes are a larger supply pipe from the water main, a pump, or an accumulator.

Pressure that was fine and dropped suddenly. Suspect a new leak, water company works, or a failed pressure reducing valve. Worth checking quickly. Check for leaks first, then contact the water company, then have the valve inspected. Our guide to water pressure that has suddenly dropped walks through it.

Understanding the numbers

Water pressure is measured in bar, or sometimes in PSI (pounds per square inch).

• Below 1 bar. Very low. Most appliances will not work properly, and showers are close to unusable.
• 1 to 2 bar. Adequate for basics, but showers will be weak and some appliances struggle.
• 2 to 3 bar. Good. Everything works, showers are satisfying, and more than one outlet can run at once.
• 3 to 4 bar. Excellent, though you may need a reducer to protect appliances.
• Above 4 bar. Too high. Can damage appliances and cause leaks, and it wastes water. A pressure reducer is essential.

You can buy a pressure gauge for ten to twenty pounds that screws onto an outside tap, which tells you exactly where you stand before you spend money on a solution.