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Isolation Valve

by | 22 Sep 20 | Help and Advice | 13 comments

What Is An Isolation Valve?

An isolation valve is a fitting within the plumbing pipework.  They are also referred to as service valves.  As the name suggests it can either allow water to flow or stop water from flowing.  Exactly why would you need to turn off your isolation or service valve?


Reasons For Turning Off 

Two of the main reasons, when you will need to turn off your water supply via an isolation valve, can be either when as a tenant or a homeowner you may need to locate one immediately due to a leak in their property or you are having a tap changed or other plumbing work being done in your property and you need to locate your isolation valve fast.  

For some of us not so DIYers, we have no idea what it looks like, much less how to turn one-off.  In the United Kingdom, it is a legal requirement for water distribution pipework (AKA plumbing pipework) to have an adequate number of service valves/ isolation valves within your property.  Please click here for further guidance:



Flathead Isolation Valve

Where To Locate Valve

First things first, locating your isolation valve.  These are normally in places you would never think of looking i.e. in airing cupboards, under your stairs, even under the floorboards, just to name a few places.

Do not get confused between a stopcock and an isolation or service valve.  If you have found the mains water shut off valve located outside your property or at the entrance right in front of your gate. Then you are looking at the wrong plumbing part, as this is a stopcock and not an isolation or service valve.

As the name states, an isolation valve or service valve should if plumbed correctly be located for example under your handbasin or kitchen sink. Even your toilet or boiler will have a few isolation valves.  This is one plumbing item in your home that you need to know its location just like the back of your hand. This can save you hundreds of pounds by not having to call an emergency plumber at 3 AM.


Different Types of Isolation Valve

Photo of an isolation valve on a blue background
Photo of a turn style isolation valve on a blue background
Photo showing flathead isolation valve
Photo showing turn style isolation valve with a blue knob.

Turning Off The Isolation Valve

Now that you have located your isolation valve, the next question is, exactly how do you turn it off.  In order to turn this off, you at times need to exercise a bit of patience.  This is primarily because if you have never before had the need to turn it off, then it may be a bit stiff.  The use of WD40 will come in handy at this point (for a photo of what the can looks like, please see below).  If the flathead at the top of the isolation valve is stiff, spray some of the WD40 on it, wait about a minute then try again.  Be careful not to force the flat head because you may cause this to be rounded off then you may have to change the entire isolation valve.  Although there are some with a handle that you just turn in the off position to turn the water off, the one we will be concentrating on is the one with the flathead.  Just when you thought it would be that easy.

Flathead Isolation Valve

Don’t Panic


The first thing to do is don’t panic.  It is not that difficult to turn off your isolation valve.  Turning your isolation valve off for the first time is new, however, you will be a pro in no time. Read the required steps below.

After you have managed to turn off your isolation valve  yourself,  you will be like, that’s it!  Yep that’s it.  Wasn’t that difficult was it.


Photo of empty toilet roll with don't panic written on it.
Set of three screwdrivers in the colour red.

Tool Required and Steps To Take

First things first, you are going to need a screwdriver, a decent flat headed screwdriver. 

Secondly, place this screwdriver in the flathead section of the plumbing fitting, which is always located at the top of the isolation valve in the middle of the fitting.  Now you have located it, just how you will know that it is on or off?  If the flathead on the isolation valve is following the pipework, then your water is on.  To turn this off, all you would need to do is to turn it ever so slightly a quarter turn 90 degrees either to the left or to the right.  When the flathead is no longer straight and is in the opposite direction then ta da, you have managed to turn off your isolation valve. Remember as stated above, if slightly stiff, spray the trusted WD40. If you want to double check then open up a tap to ensure the water stops flowing.

Routine Care

You may be thinking to yourself, routine care? What is this?  Don’t stress yourself too much as it is not as bad as it sounds.  The flathead at the top of the isolation valve can sometimes become stiff especially if not used in a while.  The use of the trusted WD40 or other brands comes in handy.  Every so often we would recommend that you spray some WD40 and turn it on and off just to loosen up the flathead a little.  Primarily because overtime, the head becomes a bit brittle and it may become more difficult to turn it off when needed urgently.

At times, there is a leak in your property from either a burst pipe or a leaking tap, then if you follow the above instructions then you have managed to stop this leak.

Sometimes turning off an isolation or service valve can result in a little drip from the valve body. This is usally because the little oring buried in the valve body is worn or split. Most of the time turning the valve back on will stop this little drip. Unfortunately if it does not then a new valve we be needed. 

Photo with person holding can of WD40.  In the background is website
Do You Need Further Help?


Living in North or East London area and you think this is too much work for you and you would rather contact the professionals, then you can contact us for further assistance.  We are available 24hrs/365 days.