What do you do with the old hot water tap?

What do you do with the old hot water tap when connecting a cold fill washing machine?

washing machine blanking cap The old hot water tap should be capped off by screwing a special blanking cap onto it (but first see update below). This is wise because I’ve heard of several cases where the unused hot tap has eventually started to drip, or even where the lever has been accidentally knocked partially on later. This can happen if the hot tap is in the kitchen sink cupboard. I’ve also seen cases where the washing machine itself moved about and knocked the lever when the hot tap was behind the washing machine. This isn’t so likely if your old hot water tap is a proper screw type but the ubiquitous red and blue lever taps are more prone to these issues and it’s safer to blank off any old unused washing machine tap, especially if they are installed out of sight.

Warning about buying blanking caps from DIY stores

I visited several major DIY stores including Wickes and B&Q trying to find a blanking cap for my old hot water tap. They only seemed to stock one blanking cap that looked anything like what I was after but after buying it and opening it, it was just fractionally the wrong size. Presumably it’s designed to cap off some other plumbing requirement. If I remember right I think it was 22 mm – I can’t recall, but I remember taking it over to an actual hot tap at Wickes and through the plastic packaging of both parts it did appear to be the right size. It wasn’t. The size you need if you want to try and source one from a shop is – 3/4″ Brass blanking cap and washer (which is around 19 mm).

washing machine blanking cap Recommended source to buy blanking cap: It took me several wasted visits to large DIY stores, one wasted purchase (of one that was the wrong size) and a lot of time searching the Internet to find this product and I found a good source and linked to it. Sadly it appears they have closed down now, so the best I can recommend is that you search Google for “3/4″ Brass blanking cap and washer” or specifically ask for that at DIY stores or plumbing merchants. The seal is needed for proper sealing off of the old tap but if you don’t get one, try using one from the old hot fill hose.

Important update: Dead leg in plumbing

Update This article has just received a small comment from Collin Lewis asking – “Doesn’t blanking off the hot water pipe at the valve create a “dead leg” allowing bacteria to develop?

I had never heard of this but within seconds I could work out exactly what he was referring to and so I spent some time researching the issue. When a length of pipework is capped off so that no water flows through it any longer all of the water inside the pipe becomes trapped. Because the tap is never turned on, this water stays trapped for ever and can apparently develop bacteria inside, which could in theory drift into the rest of the pipework.

I found this site which starkly states that dead legs in pipework are a major cause of Legionnaires’ disease UK urged to follow Europe and tackle ‘dead leg’ plumbing. I am still researching the issue in an attempt to work out how serious this actually is. Is it a theoretical threat? Does it only affect other countries i.e. hotter ones? Is it only a concern on cold water pipework, which we drink? All of these questions I hope to find the answers to shortly and will update this article accordingly. For now it is wise to be aware of the potential issue and best practice should be to have any redundant pipework removed altogether. This unfortunately means most people will need a plumber.

Another potential issue is that you might not want to have the pipework removed in case it is ever needed again in the future. This may be unlikely being as virtually all washing machines are cold fill only and have no hot water valve. However, it is not impossible to imagine a reversal of this practice and a return of the hot water valve on washing machines. I have personally pointed out several good reasons for reintroducing the hot water valve in my article on cold fill washing machines but having said that, health and safety is always an overriding concern. Keep an eye on this article for further updates.


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  1. avatar Anonymous says:

    do you fit this after the pre-existing tap (ie leave the old blue/red handle control where it is) or do you have to remove the old control piece?

  2. You just unscrew the old hot fill hose from the tap and screw the blanking cap on in its place, and of course leave the hot water tap turned off.

    Make sure the seal is fitted inside the blacking cap and tighten it firmly but there’s no need to use any tools, just nice and firm with the fingers should do. If you want to nip it up with some pipe pliers just nip it a millimetre or so past finger tight.

  3. avatar John Shuttleworth says:

    My hot fill pipe doesn’t have a dedicated tap. Whoever plumbed it in didn’t fit one. The cold and hot fill pipes to the washing machine each share stopcocks with the cold and hot fill pipes to the kitchen sink taps which will obviously have to be switched on again after installing the new, cold-fill only machine. I presume the blanking cap will be sufficient to seal off the hot water pipe at the point where the old hot fill hose currently attaches but would welcome your advice.

  4. Hello John. Yes, the cap has the same thread as the old hot fill hose so when you remove the old fill hose you screw the cap on in its place. However, ideally you’d like the tap to then be turned off so it’s not under any pressure.

    If you can’t turn off this tap because it also supplies the sink tap you will have to rely on the rubber seal inside this cap preventing leakage. It should do, but keep a close eye on it for a few weeks at least.

  5. avatar John Shuttleworth says:

    Just wanted to thank you for your help and advice. I bought the cap from e-lectricalshop.co.uk as you recommended. Excellent service – ordered Friday pm, delivered Saturday am. Fitted it Saturday and all seems fine. As you say, I will keep an eye on it for a while. Again, many thanks!

  6. Thank you for a very good and clearly written article, the information about the blanking caps was particularly helpful, and I have used your contact to order the caps I need.

    Thanks again for your information
    Bob Ashton

  7. I also just wanted to say many thanks for this, my blanking cap arrived today from E-lectricalshop.co.uk and it fits perfectly (this followed on from 3 fruitless trips to different DIY stores before I read your article).

  8. Many thanks Joanna. I wrote the article specifically to help people like yourself after having a lot of problems trying to buy one myself and it’s great to get feedback that makes it worth while.

  9. Thankyou so much for this advice. I’ve been worrying about the un-used hot water pipe for exactly the reasons you cited as well as a whole load of others including random teenage guests of my daughter fiddling with the lever, boiling hot water spewing everywhere, flooding into the hairdressers shop below etc. I was actually on the verge of ordering a 22mm compression blanking disc from somewhere or other (having spent hours trying to work out what the damned thing is called) so you’ve saved me a great deal of hassle. I shall order the right one now. Really appreciate your advice.

  10. Thanks for the excellent advice. Have ordered a blanking cap today from E-lectricalshop.co.uk saving me the hassle of wandering around DIY stores hoping to find the right part.

  11. Thank you Sarah. It’s great to see any of my articles being so useful.

  12. Found this site so useful before so hoping you can advise…
    Just taking out my old machine to make way for new one arriving tomorrow. Old machine has hot and cold – new is cold only. However hot tap when disconnected from old machine and red “valve tap” is turned off still runs. HELP!?! Dont know why as this didnt happen before – any ideas or suggestions welcome before I have to pay a plumber a fee!

  13. avatar Eric Nelson says:

    Looking for the cap in white plastic, are they available?

  14. I wouldn’t think so Eric. I wouldn’t think there was a demand for white plastic ones.

    Sam: Chances are your tap is broken. It’s extremely common with the ubiquitous red and blue tabbed taps most plumbers use. The plastic used for the levers isn’t of good enough quality and they break. This results in you thinking you’ve turned the tap off but the plastic lever hasn’t really turned the metal valve. Either that or it’s turned it almost off but can’t turn it completely off because of another common problem with these taps where they go very stiff.

    The answer is to remove the plastic lever and use pliers to turn the tap off and then use the blanking cap. Otherwise you’d need a plumber to replace the tap.

  15. avatar Eric Nelson says:

    Thanks for thr response much appreciated

  16. I can only endorse the comments above. I ordered from the supplier as suggested, and the part arrived in a couple of days and fitted perfectly. The internet, I’ve found, is a remarkable resource for self-help and self-instruction in so many areas, from advice on addressing nagging worries as in this case, or on sealing a shower tray, to finding recipes for baking terrific cakes and breads, but only because decent people who know what they’re talking about are prepared to share what they know. Many thanks.

  17. Thank you so much for the above information. I was a little dismayed when my new machine arrived this afternoon, only to be told I needed some cap that I had never heard of. It was such a help reading your advice, and even better, I discovered that I live less than 8 miles from their shop – so have just been there in person to pick up the cap.
    Many thanks!

  18. avatar Ross Foley says:

    A friend has moved to a new house. She has an eight year old Indesit washing machine with both hot and cold fill. However, in the house she has moved to, the hot feed has been stop-ended. She is worried that she can’t use the machine with the hot fill hose attached or with an open fill hole if the hose is removed. Do you know if these machines have a non-return valve to prevent water being forced out of the hot fill hole? If not, do you know where we might be able to get a stop for that hole? Thanks in anticipation for any help you can give so that I could set her mind at rest.

  19. Thanks Keith and Hannah.

    Ross: She can use it by connecting the hot and cold hoses to the single cold supply. This might help Is it possible to use a hot & cold fill washing machine with just a cold supply?

  20. Ordered one of the brass blanking caps from e-lectricalshop.co.uk on Wednesday afternoon, arrived this morning. Saved lots of time rummaging around the DIY stores trying to find the right one.

    I notice that it has a full rubber insert rather than the usual type washer – assume this is OK?

  21. Thanks Steve, yes I would presume it’s OK too.

  22. Thank you so much-this has helped so much (just got a new washing machine and its single valve…)

    I would be lost if it wasnt for this guide!

  23. I cannot thank you enough for your advice here which I found via Google. I recently got a new washer with just a cold fill behind it instead of the old hot & cold. I recently noticed the floor getting wet around it and found the red plastic lever causing a drip. Getting to a DIY store is difficult at the best of times as I don’t drive so your warning there was timely. I followed your link to e-lctricalshop.co.uk – blanking cap (£2.99) came 2 days later and fits brilliantly.

    I’m not exaggerating to say you’re my hero for providing this valuable advice. Thanks to you this non-DIYer woman got this sorted out with little fuss. I have whitegoodshelp on my bookmarks list now!

  24. Thanks very much Gavin and Carol: This is proving to be my most popular bit of advice. I’m really pleased it’s helped so many people.

  25. Thanks for the excellent tip.
    Ordered Friday arrived Monday morning via Royal Mail.

    As a temporary measure you could use the old red or blue, round, plastic connector that came off the old hoses.
    By inserting a 10p piece into it,covering the hole, and then add the washer.
    This is what I did until the correct blanking cap arrived.

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