How do you blank off the old hot water tap?

Hot tap for washing machine

For the last 20 years or so, most people in the UK have not needed a hot water tap for their washing machine. So what should you do with yours? Just ignore it – or blank it off?

What should you do with the unused hot tap?

There are 4 options. Some may seem inconvenient, but there could be good reasons to consider them –

  1. Just forget about it and leave it where it is
  2. Cap it off with a blanking cap
  3. Remove tap and all pipework branching off from the main pipe
  4. Leave hot hose attached and regularly flush hot water through the unused pipework (my personal choice)

Leave everything as it is and do nothing

1: This is the easiest option, already taken by most people, who just stopped using the hot tap and forgot about it. For most people, it’s probably OK to do this…

However, when I found out that dangerous bacteria could build up inside the unused pipes, and contaminate the water supply, I became concerned (explained later…)

Fit a blanking cap to cap it off

2: If leaving everything as it is, but just no longer using the hot tap, you might want to fit a blanking cap to ensure no water can escape from it as it’s not connected to anything. You may be concerned that someone could inadvertently turn it on, causing water damage.

Or, depending on where the tap is situated, you might worry that it could get slightly knocked, and start dribbling water. This is especially true if the tap is inside a cupboard and has plastic levers to turn it on.

Tap capped off to stop accidental water leakage
blacking cap for tap

Don’t fit a blanking cap without understanding this entire article first

Buying a blanking cap for the old hot tap

If you decide to cap off the unused tap, you need a specific size of blanking cap. The size you require if you want to source one from a shop is – 3/4″ (which is around 19 mm). You could also buy it from Amazon (paid link) – Buy 3/4″ Brass blanking cap and washer

You should also be able to buy one from any plumbers merchant or DIY store. The cap should come with a rubber seal. If it doesn’t, try using the old seal from the hot water pipe.

You should consider removing the unused tap and pipework

3: When a water tap is not used any more, water ceases to flow through all the pipework that branches off from the main pipe to the tap. The water trapped inside becomes stagnant.

If conditions allow, bacteria and other microorganisms can grow inside that can break off and get into the rest of the water supply.

I did a lot of research about this issue, and became convinced that there could be a potential health issue for some people. (There’s a link at the bottom of this article to fully explain this).

Leave hot hose attached – and flush regularly

4: This is a solution if you are concerned about the potential growth of microorganisms and bacteria described in my companion article (link at end of this article) – but you don’t want to have unused pipework removed. It doesn’t need a plumber, and the hot tap is retained in case it’s ever needed again. You never know if hot and cold fill washing machines might return.

I’ve left my hot fill hose connected to the hot tap, but just hung up out of the way. I have a monthly reminder set up on my phone to run the hot water tap until piping hot water flows through it. This kills bacteria and replaces the stagnant water.

You could flush the hot water into a sink, a bucket, or the washing machine’s standpipe. The point is to have (60 degrees) hot water flowing through all the dead pipework. This should flush away stagnant water, and kill off and remove any microorganisms, or bacteria.

By the way, this option is easy for me. My washing machine is in the garage. It’s easy to access the hoses and standpipe. But it may not be practical for everyone. If it isn’t for you, then you’ll need to choose one of the other options.

How long do I run the hot water for? I usually do it for 30 seconds of hot water flow, but I’ve seen advice saying run for longer – and once a week! We all need to make an informed decision, which should be based on a proper understanding of the issue, and the configuration of our own plumbing setup.

If you believe there is a potential health risk, you should have the dead leg pipework removed properly. Read on for a much better understanding of how real this risk is for you, and your circumstances.

Is the dead leg health risk a genuinely serious issue?

Read my follow-up article, which explains the issue in full detail, so that you will be able to make an informed choice – potential health risks in not using old hot water tap.

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119 thoughts on “How do you blank off the old hot water tap?”

  1. Appreciate the advice re 1) blanking cap for hot water supply 2) and potential unhealthy dead water in old pipework run to washer.

    The remedy being to remove the surplus piping relating to the stagnant stretch.

    Would it not be possible reuse that hot water feed into the adjacent hot water outlet just to move the water,.

    You would have thought manufacturers would have been aware of the potential health issues of moving to a cold fill or just wanted to offer choice & options.

    and therefore have an optional hot water inlet to obviate the H&S problem, to drain or utilise an amount of water from the stagnant water automatically every so often.via some controller options.

    I always suspect some like going in circles

  2. Hello Shaun. You make a very good point about manufacturers, they presumably had no idea that blanking off the hot water tap could lead to dangerous bacteria. To be fair, I only learnt about it myself several months back.

    I have considered joining my hot and cold water hoses together using a y-piece connector which would regularly use the hot water and stop it going stagnant. The problem with this approach though is that modern washing machines and detergents are designed to work from cold water. In many cases though there wouldn’t be much hot water going into the machine because they take a while to run hot (unless supplied via a combi boiler close to the machine) and they don;t take much water in on wash. However, the hot tap would need to be turned off after the initial wash fill otherwise it would use a lot of hot water on rinses.

  3. can you help please my mum is moving into a flat , but were the washing machine goes theres only 1 pipe to connect to washing maching to and the lever is red can I connect it to the red pipe or does it only have to be blue . And what to do if theres to pipes comin of tge waa

  4. A red indicator on a tap doesn’t mean it’s definitely a hot water tap. It’s supposed to indicate a hot water tap but there’s no difference between a hot and a cold water tap at all and the red or blue indicators are just there to help users. Someone could have used a red one instead of blue. To find out if it’s hot or cold water attach a fill hose and run water into a bowl or bucket for a minute or so and see what comes out. If it’s cold you can use it fine, if it’s hot then someone plumbed it in wrong or connected it up for a dishwasher (some of which can use hot water) and it needs a proper cold water supply to use with a washing machine.

  5. My mum has an old Servis M3001 washing machine and during the process of fixing a leaky hot tap valve I noticed that the machine has like a small red blanking cap fitted where the hot hose used to connect to the machine. The hose will still connect to the machine but it looks like this stops any hot water going in. Is this a common thing, I’ve never seen this before? I can’t find the old manual to verify whether the machine is cold fill only.

  6. Ian, if it has two water valves it is definitely a hot and cold fill washing machine. Cold fill washing machines will only have one valve.

    Looking at Ransom Spares there is definitely a hot water valve listed for that model – washing machine water valves

    I can also see there is a hot water valve closing cap listed too. I’ve never come across this and I’m surprised that they would make a washing machine designed to use hot and cold water but then create a part to blank off the hot valve. However, if the washing machine is working ok on all the wash cycles I wouldn’t change anything.

  7. notalberteinstein

    Re earlier comments about blanking plug thread, it may be useful to know that 19mm = 0.748 inch. Which is practically the same as 3/4 inch.

  8. Andy Trigg (Whitegoodshelp)

    Hello Liz. I describe what you need in the first couple of paragraphs. If you search for, “3/4 Brass blanking cap and washer” on Google you should find plenty of places that sell them.

  9. Dear Andy,
    I have been trying to get onto the website to order a blanking cap for old hot tap when connecting a cold fill only washing machine but when I click on “go to website” the page comes up saying “we’re closing down Talk Talk webspace”. Then when I click on “continue to browse” I get the message “NOT FOUND the requested URL/jmistone was not found on this server”.
    I notice the comments posted on your website are all from 2010. Can this mean E-lectricalshop website no longer exist?
    Any advice regarding this problem would be most welcome including any other website where I can get a suitable blanking cap from.
    Thanking you for your help,
    John Smithb

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