Low water pressure in house has five main causes: weak mains supply, a part-closed stop tap, blocked or restricted pipes, a faulty pressure reducing valve and a hidden leak. A single tap or shower can also be the problem on its own.
Low water pressure can make simple jobs around the house frustrating. Your shower may feel weak, taps may take longer to fill a sink, or several outlets may struggle when used at the same time.
If you have low water pressure in your house, the cause is not always obvious. It could be a problem with the main supply, your internal pipework, a valve, or a hidden leak.
I usually start by checking whether the problem affects the whole property or just one tap or fitting. This helps narrow down where the fault may be.
What causes low water pressure in a house?
There are several possible causes. Some are simple to fix, while others need a closer inspection.
1. Low mains water pressure
The problem may be outside your property.
Your local water supply may have low pressure, particularly at certain times of the day. If your neighbours are experiencing the same issue, this could point to a mains supply problem.
I would check whether the pressure is low throughout the house. If every tap and shower is affected, the incoming supply is one of the first things I would consider.
2. A partially closed stop tap
Your stop tap controls the water entering your property.
If it has been partly closed, it can restrict the flow of water. This can happen after plumbing work or maintenance.
I would check that the stop tap is fully open. Do not force it if it is stiff, as this could cause damage.
3. Blocked or restricted pipes
Older plumbing systems can develop restrictions inside the pipework.
Limescale, corrosion or other build-up can reduce the amount of water flowing through a pipe. This can be more noticeable in older properties.
If only one area of the house has low pressure, the problem may be closer to that fitting rather than with the main water supply.
4. A faulty pressure reducing valve
Some properties have a pressure reducing valve (PRV) to control incoming water pressure.
If the valve becomes faulty or is set incorrectly, it can reduce the pressure available around the property.
A PRV needs to be checked properly rather than simply adjusted without finding out what is causing the problem.
5. A hidden water leak
A leak can also cause a noticeable drop in water pressure.
This is particularly important if the pressure has suddenly changed and there is no obvious reason for it.
You may also notice a damp patch, unexplained increase in water use, dripping sounds or water around pipework. However, a hidden leak does not always give you an obvious warning.
If I suspect a leak, I would recommend investigating it rather than ignoring the change.
You can find out more about water leak detection and how hidden leaks can be traced and repaired.
6. Problems with a tap, shower or fitting
If the low pressure only affects one tap or shower, the problem may be local.
The aerator, showerhead or valve could be blocked or restricted. In this situation, the rest of your water supply may be working normally.
I would check the affected fitting before assuming there is a wider plumbing problem.
How can I fix low water pressure?
The right fix depends on the cause.
There are a few basic checks you can make:
- Check whether the problem affects the whole house.
- Check that your stop tap is fully open.
- Compare different taps and showers.
- Ask neighbours if they have noticed a similar problem.
- Look for signs of a water leak.
- Check whether the problem started after recent plumbing work.
If the problem continues, I would recommend having the system checked by a qualified plumber. Trying to adjust valves or alter pipework without knowing what is wrong can make the problem worse.
What if the water pressure suddenly drops?
A sudden change is worth investigating.
If your water pressure was normal and has suddenly become weak, I would look for a change in the system. This could include a leak, a valve problem, damaged pipework or an issue with the incoming supply.
A sudden drop should not simply be treated as something you have to live with.
If you cannot find an obvious cause, professional testing can help identify where the restriction or pressure loss is occurring.
When should I call a plumber?
If low water pressure is affecting several areas of your home, keeps returning, or has appeared suddenly, it is sensible to get it checked.
I can inspect the plumbing system and work out whether the problem is related to the incoming supply, internal pipework, a pressure reducing valve or a leak.
R.W. Miller provides plumbing services across South London and Surrey. I can also investigate suspected water leaks and other plumbing problems.
The Bottom Line
Low water pressure in the house can have several causes. It may be something simple, such as a partly closed stop tap, or it could point to a problem with pipework, a pressure reducing valve or a hidden leak.
I would not recommend guessing at the cause. Start with the simple checks, then get the system inspected if the problem continues.
R.W. Miller Plumbing & Heating provides plumbing and water leak detection services across South London and Surrey, including Wandsworth and Lambeth. If you are struggling with low water pressure, call 07375 813996 or get in touch and I can help identify the cause and explain the best way to fix it.
