In this article, we are going to talk about how you can fix a leaking isolation valve. These valves are often used in the process of isolating hot or cold water from your home’s pipes so that they can be serviced without risking damage to the entire system. This leakage could result in major issues for both you and your family because it may cause flooding or lead to an accidental scalding incident. You need to be aware that if you attempt to fix this issue without the proper knowledge and equipment, there is a risk of causing more damage. This article is intended to provide you with some guidance on what your options are when it comes to repairing an isolation valve leak. If you have located an isolation valve leaking from the screw and are not confident in doing the work yourself, call in a pro.

Ballafix Valve

What is an Isolation Valve?

Isolation valves are categorised by their function rather than design. The isolation valve is a crucial component of any pipework system, as it is used for controlling the flow and/or direction of media in a process system. To easily understand the concept of an isolation valve, think about how a tap works in your kitchen or bathroom. Normally the valves are left open so that you can control the water flow with the tap above.

If there is something wrong with one of those taps and you need to carry out some work, the isolation valves can be closed to stop the flow of water.

Why is my Isolation Valve Leaking?

There are a few possible reasons for a leaking isolation valve.


The most common reason for an isolation valve to leak would be age-related wear and tear (given moderate use). This is a simple fact of life when working with anything that has moving parts.

Cheap Parts

Isolation valves are designed to withstand extremely high pressures. If your system has had cheap parts installed, this could be the reason that it has failed. Poor parts made with cheap materials are not likely to last in such an environment. For the sake of a few extra pence, ensure that the parts you have fitted are up to the job.

Build Up of Dirt/ Limescale

Yes, you can get limescale inside your water and heating systems although this is obviously much more prevalent in areas that have a less than ideal water quality. Dirt and limescale can interfere with the function of the isolation valve and even cause seals to fail.

Isolation Valve
Isolation Valve

Tips to Stop an Isolation Valve Leaking

In truth, if you find that you have an isolation valve that is leaking (especially from the screw) – it is time to get a replacement. The tips I am about to give you are more of a short-term measure and not expected to last long-term.

Move the Screw

Yes, slowly moving the screw to see if whatever has caused the leak will right itself. This does work occasionally, and you may get lucky and stop the leak from causing any damage before it gets worse. However, as I mentioned, once the isolation valve has shown signs of failing, you will need to replace the part sooner rather than later.


Yes, this one seems a little counterintuitive, but I have known isolation valves to right themselves on their own. As long as the leak is a minor dripping and you are not losing too much water, just cover the valve with a cloth (to absorb the water) and then place a bucket or large bowl underneath to catch the water from the cloth.

Leave the valve for an hour or 2. If the leak has stopped – great, you have bought yourself a little time, if not, it is time to replace the valve immediately.

How to Replace a Leaking Isolation Valve

There are a couple of things that you will need to do this job quickly and efficiently and I am sure that you already have them in your house somewhere.

What You Need

  • Pipe Wrench or adjustable spanner x 2
  • Large Bowl or a bucket
  • Cloth
  • New full bore lever valve (Amazon link – opens in a new tab)

Step 1 – Turn Off the Water

The obvious first step is to turn off the mains water coming into the house. This can be done by locating the main isolation valve on the pipe coming into the house or by locating the stopcock which is usually outside the house under the street.

Step 2 – Crack the First Nut

Now, you will need both pipe wrenches or, adjustable spanners. Using one spanner to hold the first nut in place, take the second spanner and turn the second nut anticlockwise. The nut will initially be stiff but after it has cracked (first 1/4 turn) it will become easier.

Step 3 – Catch any Water

There will be a little leftover water inside the pipe, so as you undo the first nut that you cracked, prepare the bowl or the bucket to catch any water that will escape when the joint has been fully opened.

Once the nut has been undone, leave it in place.

Step 4 – Remove Second Nut

Next up, you will want to remove the second nut, this one can be a little trickier as you will need to get a grip on the ballafix valve and crack the leftover nut. Once this has been cracked, they are generally able to be undone with your fingers.

Step 5 – Remove the Valve

With both ends undone, the valve can be removed. You will want to ensure that you leave the olives and nuts in place as they can be used for the new full-bore valve.

Step 6 – Insert New Valve

Now you will be able to fit in the new valve using the existing olives and nuts to ensure a good seal.

Make sure that you tighten the nuts properly – you do not want a leak when the water goes back on!

Step 7 – Clean Up and Test

The moment of truth! Take your rag and have a quick clean-up of the area and then turn the water back on. Depending on where you have fit the new valve, you may want another pair of eyes on the new valve whilst you are turning the water on to ensure that the joint is properly sealed.


Isolator valves can be found all over your house, in the bathroom, kitchen, airing cupboard and more. If your isolator valve is leaking from the screw, it is time to replace it. You may be able to stop the flow initially, but I would not recommend this as a long-term solution and replacing these valves is a relatively simple task that can be performed by almost anyone. We recommend buying parts that are up to the job and not cheaply made parts that may end up causing you more issues in the future. The part that we recommend is the full-bore isolator valve.

Why is my Isolation Valve Leaking Infographic

Plumbing Wizard Tips

“Remember to turn the water off before doing any work on existing fittings – you do not want to flood your house!”

“If you are unsure, call a professional – just make sure that they fit a good quality part as I’m sure that’s what you will be charged for!”

“If you manage to stop the valve from leaking, use this time to go out and get a better part ready to fit asap!”

“A few more pence spent on a better part now may save you quite a few £££’s later on!”

Frequently Asked Questions

Can isolation valves leak?

All valves have the potential to leak depending on their age and quality. Cheaper isolation valves are known to be of poor quality so I would avoid them at all costs.

Do isolation valves fail?

Anything that has moving parts has the potential to fail. Ensure you invest in quality parts that are likely to have been engineered to a higher standard. They may be a little more expensive, but it is worth it.

Can you fix a leaking ball valve?

Ultimately, No. You cannot fix a ball valve once it has sprung a leak. You may be able to stop the leak by turning the screw a little, but this is a short-term solution, and the valves require replacing asap.

What to do if the isolation valve won’t turn off?

If your isolation valve has seized and won’t turn off, you will need to replace it asap. A seized isolation valve is useless and not doing its job properly.

What is an isolation valve and why is it important?

An isolation valve is a type of plumbing valve that can be used to control the flow of water to a specific area of a plumbing system. It is important because it allows for the isolation of a specific area for repairs or maintenance without shutting off the water supply to the entire system.

What are the signs of a leaking isolation valve?

Signs of a leaking isolation valve include water leaks from the valve itself, a decrease in water pressure, and an increase in water bills.

How do I fix a leaking isolation valve?

If your isolation valve has developed a fault, it is best to isolate the area and replace the valve altogether.

What are the dangers of a leaking isolation valve?

A leaking isolation valve can cause water damage and can lead to an increase in water bills. It’s important to fix a leaking isolation valve as soon as possible to prevent further damage.

Can a leaking isolation valve be a sign of a larger problem?

A leaking isolation valve can be a sign of a larger problem, such as corrosion or damage to the valve or the surrounding pipes.

Can a leaking isolation valve cause low water pressure?

Yes, a leaking isolation valve can cause low water pressure if the water is leaking out of the valve instead of flowing through the pipes.

How do I know if my isolation valve needs to be replaced?

If your isolation valve is leaking, it may need to be replaced. Additionally, if the valve is old or showing signs of wear and tear, it may be necessary to replace it.

Can I install an isolation valve on an existing plumbing system?

Yes, it is possible to install an isolation valve on an existing plumbing system.


Lee Pearce is not just a master plumber; he’s a veritable Plumbing Wizard. With over 30 years of experience in the trenches of pipes and drains, Lee has become the go-to sage for DIY plumbing, saving homeowners thousands in potential call-out charges. As the founder of Plumbing Wizard, he’s dedicated to demystifying the complexities of home plumbing, offering easy-to-follow advice that stands the test of time and pressure. His online blog is a treasure trove of tips, tricks, and tutorials that empower everyday individuals to take charge of their home’s plumbing health. Lee’s practical wisdom is not just about fixing leaks; it’s about imparting confidence and self-reliance. When he’s not writing or elbow-deep in a plumbing project, Lee is passionate about educating the next generation of DIYers, ensuring that practical skills are passed down and preserved.

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