Leaking isolator valve?

I was always told when you renovate a house you take off one bit to expose more problems. This was certainly the case for my vision of upgrading my central heating system. I have a strong opinion on how radiators should look in a house. In order to put new radiators in, I would have to drain the system to modify the pipes. The only problem here was that I didn’t have a drain point. This was intended to be the first job of until I came across a pair of isolator valves on the central heating line…

The Isolator Valve

I happened to find the two isolator valves on the flow and the return on the lowest accessible point on the central heating. In practice I thought

“Great, this means I can close the two isolator valves and only drain a small portion of the central heating on one side of the isolator valves.”

The isolator valve needs a flat head screwdriver to turn the ball valve (ballofix) inside. When it is parallel to the pipes it means the water can flow through. I turned one of the isolator valves to close it. Instantly the water started leaking from the middle of the fixing at an alarming rate. What was meant to make the job easier had just made the overall job a lot harder!

Where are they normally used?

You generally find these on the cold water pipe to a toilet or bathroom sink supply. Whilst the idea of them seems great to be able to close sections of central heating off, the reality is just too problematic to be able to go away and not worry about them giving way to your central heating!

And I found them?

What can you do with the broken isolator valve?

In almost 100% of the cases you will have to replace the valve. I’d recommend not replacing it with another isolator valve. One of the top google suggestions for this type of valve is ‘Isolator valve leaking’. What might work as a temporary measure is to slightly adjust the angle of the valve left or right. This may help reseal it until you manage to get the parts you need. The most common issue seems to be the rubber seal behind the valve degrading and as soon as there is disturbance, the water tight seal is broken.

Even though one of the isolator valves was leaking I decided to replace both on the flow and return as it would make sense to work with a drained system just once.

There used to be an old radiator that was T’d off next to these valves which had a compression stop joint. As the valve was leaking I undid one of these stop ends to start draining into a bucket. I’d recommend getting a pipe so you can drain straight outside. Filling a bucket, closing the stop end, emptying the bucket and repeat took forever.

Once drained

I loosened the compression fitting of the isolator valve to let the remaining water spill out. Maneuvering the pipes brought out more water than I thought was there so just loosening the leaking isolator valve first was necessary.

What to replace the isolator valves with

I used compression repair couplers in place of the isolator valve. I didn’t have a need to close off part of the central heating in the future and didn’t want to invite problems down the line. Another thing to note is that the internal diameter of the pipe reduces the flow to the central heating. A 15mm isolator valve ends up having an 8mm diameter on the inside once you take the fitting into account. This would mean an unequal pressure at this point in the central heating compared to the rest of the line.

What I like about these repair couplers is that they can work with a range of gaps to repair rather than a set length. If you cut the pipe at a set distance you don’t need to worry for being a few mm off. Be sure to get the correct width for your system which would most likely be 15mm. Due to the time urgency I got mine from screwfix.

Things to note

How tight is tight?

You can always tighten a compression fitting more if it is too loose and leaks water. Whereas if you overtighten it, you’ve most likely ruined the fitting. A guideline would be to finger tighten then one turn with a wrench as a starting point.

Jointing Compound

You should use jointing compound with PTFE. You apply this to the threads of the fitting and it acts as an additional layer to ensure no water can come out. I swear by this for any compression fitting and all my valves have it on. Fingers crossed I haven’t found a single leak!

Preparation

Prep is key. I believe it’s the reason I managed to get it right first time. As you can see my copper pipes were painted at some point. You can’t ensure a watertight seal when the surface has paint and other buildup on it. To remove the paint and dirt you need the copper to look brand new again. Using a mesh like this takes off all that paint and grime to start from a good base.

Also if you need to cut pipes, get a dedicated pipe cutter. I have cut pipes with hacksaws before and getting a clean cut is a nightmare. You also need to deburr your cut.

Testing

From a DIY standpoint I don’t have all the tools available. So to test you have to repressurise the wholesystem to see if your fittings have held. Because I had a whole system of modifications to do it was more time effective for me to test the system at the end of all the modifications. This would be more efficient than constantly draining and filling the central heating.

Upgrades

Whilst the system is drained consider making any upgrades you may want to do down the line. I didn’t plan it well so had the system refilled before realising the benefits of adding a magnetic filter!