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Combi Boilers - Hot Water

Dog BreathDog Breath Posts: 314
edited October 2016 in The cake stop
My elderly parents have a problem with their hot water system. Central heating is working fine, but they are only getting hot water out of the bath tap. The bathroom basin and kitchen hot taps are not delivereing any water. All the cold taps are working normally.

I hope that it's just knackered taps/washers and is just these that need replacing or repairing. I've read various things about diverter valves on the boiler which diverts the cold water through the heat exchanger to deliver hot water. I'm assuming if this was faulty, there wouldn't be any hot water. But as there is hot water through one tap, I guess this isn't the problem.

Any thoughts from the collective before I start to dismantle the whole system ?

Cheers
DB
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  • thistle_(mbnw)thistle_(mbnw) Posts: 3,346
    Is it a combi boiler system?

    I'd be surprised if all the taps (apart from the bath tap) have broken at the same time.

    Do they live in a bungalow or is it 2 storeys? How much water are they getting out of the bath tap? (Could the pressure in the system be so low that the water can only get as high as the bath tap?). However if it's a combi boiler and the hot water pressure was that low you wouldn't be getting much out of the cold taps either.

    Are there isolation valves on all the taps? If there are you could turn off the valve, disconnect the tap, open the valve and see if water comes out of the pipe. That might tell you if it's the tap at fault.

    I've got a problem with one of my hot taps: If I open the tap a bit then hot water comes out then suddenly stops, open it a bit more and it comes out again then stops suddenly. I have to open it almost all the way to get anything out. I think this is a problem with the washer but I've never got around to looking into it.
  • plowmarplowmar Posts: 1,032
    Sorry if I'm stating the obvious here, but do your parents have a service contract?. If so the solution may be there.

    If not are all the hot taps served by one pipe or individual pipes?. If seperate pipes are they all hot/warm coming from the boiler could be a blockage after the bathroom and before the remainder of the pipes.

    Is the boiler newish may still be under warranty.

    Worth checking the water pressure - should be approx one bar when operating, lot less when cold.

    Have you checked isolation valves to see if they are open? - they should be found just below the sinks and close to the taps.
  • Lycra-BykaLycra-Byka Posts: 292
    Defo check iso valves first, trace from boiler to taps. Sounds like the most obvious fault. The lever type are easy to accidentally knock to turn off.

    Otherwise it's a boiler problem. Chances are its not though. Boilers usually have one pump and one water 'out' pipe ie all water fed out of boiler through one pipe, then branched off from there.
  • You say they are not delivering any water if this is no water then it's a blockage or valve turned off, combi's have one outlet for hot water if one tap is ok. the rest should be. You say "elderly parents " beware they are devils for fiddling & "what does this do", a tactful quizzing plus searching for a closed valve may be reqd.
  • Dog BreathDog Breath Posts: 314
    Thanks for the info. I'll certainly check the isolation valves.

    The house is a 2 storey semi, and the boiler is situated in an old airing cupboard in the bathroom on the upper floor. It seems strange that the bath tap runs hot, but nothing comes out of the hot tap in the basin in the bathroom.

    I understand combi boiler systems should not get air locks in them, unlike older systems where the hot water is stored in a tank.

    I'm guessing the presure is OK as the boiler is fine for central heating and supplying one tap.
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  • With a combi the h/w should be delivered at near enough the same flow rate as the cold, it only passes through a heat exchanger, so as I said previously if 1 is okay they all should be.
  • diplodicusdiplodicus Posts: 546
    From what you have described sounds like it is a split in the diaphragm washer. When they split it takes a higher flow rate to activate the boiler hence why your bath hot tap works but not the others.

    Hope this helps. By the way i am a heating engineer so not just guessing :D
  • seanoconnseanoconn Posts: 5,607
    diplodicus wrote:
    From what you have described sounds like it is a split in the diaphragm washer. When they split it takes a higher flow rate to activate the boiler hence why your bath hot tap works but not the others.

    Hope this helps. By the way i am a heating engineer so not just guessing :D
    I was just about to say that..... :oops:

    Top man :D Isn't the internet brilliant.
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  • Well done that man!!!!!! we've all learnt something & today has not been in vain. That will now be stored in what I have left of a brain, hopefully to be retrieved at a later date
  • deswellerdesweller Posts: 5,271
    He has no flow - hot or cold - out of the kitchen or bathroom basin. So either the taps are binding shut or there is a blockage (assuming the isolators are not locked off). Are they using the same run of pipe from the boiler as the bath?
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  • diplodicusdiplodicus Posts: 546
    If he has no flow then my earlier post is not the answer. However more often than not when customers say no hot water out of a tap they mean they have water flow but not hot. Rereading it does look likely that in this case it is no flow :oops:

    OP have you any water at all coming out of the basin and kitchen sink tap?
  • Dog BreathDog Breath Posts: 314
    There is cold water flow from all the cold taps. Hot water flow from the bath tap. But no flow whatsoever from the other 2 hot taps.
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  • diplodicusdiplodicus Posts: 546
    It would appear then the problem is either both taps failed, or a blockage or isolation valve closed on a pipe that feeds the two non functional hot taps.

    Start at the taps. There should be a valve that turns the water off going into the combi. With the water off take the taps apart as if changing a washer. Leave apart and slowly turn water back on. If you now have flow out of the taps then you need to either ease and grease the mechanism you have removed from the tap or replace tap. If still no flow, then you need to look for a valve turned off or a blockage in a pipe that feeds these two taps but not the bath tap.

    Unless the bath backs onto the airing cupboard making it easier for the installer to run a separate feed to the bath, it is very unusual. Normally a 15mm feed will exit the boiler an all taps would be "tee'd" off this single feed.

    Let us know how you get on
  • byke68byke68 Posts: 1,070
    Methinks you need to replace the flux capacitor! :lol:
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  • adiggersadiggers Posts: 67
    Dog Breath wrote:
    My elderly parents have a problem with their hot water system. Central heating is working fine, but they are only getting hot water out of the bath tap. The bathroom basin and kitchen hot taps are not delivereing any water. All the cold taps are working normally.

    I hope that it's just knackered taps/washers and is just these that need replacing or repairing. I've read various things about diverter valves on the boiler which diverts the cold water through the heat exchanger to deliver hot water. I'm assuming if this was faulty, there wouldn't be any hot water. But as there is hot water through one tap, I guess this isn't the problem.

    Any thoughts from the collective before I start to dismantle the whole system ?

    Cheers
    DB

    me thinks if your parents are over 65(you did say elderly),and the boiler is a few years old(not A rated) they should ring one of the many companys that give them a free fitted boiler(i censored you not is no catch),before you start tampering with it.

    google tameside energy services,or nationwide,or eaga,for a few examples
    hope that helps
  • diplodicusdiplodicus Posts: 546
    If it is the boiler this is a good plan. If it isn't the boiler they will end up with a nice new boiler and two taps that still don't work.

    By the way most of these "free" boiler schemes I have come across either find "extras" that cost more than I would quote for a boiler change, or cost more in another manor :shock:
  • Dog BreathDog Breath Posts: 314
    Thanks for all the replies. I have the day off tomorrow and will be going round there to see if I can sort the problem.

    Just one thing and not sure I can do this with a combi boiler system. Can I say open the non-working tap in the bathroom, go down to the non working mixer tap in the kitchen, turn on the non-working hot tap, then put hand firmly over spout and turn on cold tap. I've read that this will force the cold water back up the hot supply pipe and clear and air locks or blockages. If the tap is open upstairs then the resultant pressure build up has somewhere to go.

    Cheers
    DB
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  • sheffsimonsheffsimon Posts: 1,282
    Dog Breath wrote:
    Thanks for all the replies. I have the day off tomorrow and will be going round there to see if I can sort the problem.

    Just one thing and not sure I can do this with a combi boiler system. Can I say open the non-working tap in the bathroom, go down to the non working mixer tap in the kitchen, turn on the non-working hot tap, then put hand firmly over spout and turn on cold tap. I've read that this will force the cold water back up the hot supply pipe and clear and air locks or blockages. If the tap is open upstairs then the resultant pressure build up has somewhere to go.

    Cheers
    DB

    Sounds like a sure-fire way to get p***ed wet through and acheive not much...wont you just have the same water pressure either side of the air lock, if indeed there is an airlock? So you wont have any "pressure build up"?

    Try it anyway, cant hurt, and might raise a laugh :)
  • Mr. halitosis canine , any answers yet?
  • Dog BreathDog Breath Posts: 314
    Spent the best part of 2 days putting my nonexistent plumbing skills to the test. I finally managed to replace both knackered taps, after much contorting under work units and cursing at siezed lock nuts, and hot water is now flowing freely in my parent's house. Thanks for all your help and advice. And no, it wasn't the flux capacitor in the end.
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  • Graham.Graham. Posts: 862
    Dog Breath wrote:
    Spent the best part of 2 days putting my nonexistent plumbing skills to the test. I finally managed to replace both knackered taps, after much contorting under work units and cursing at siezed lock nuts, and hot water is now flowing freely in my parent's house. Thanks for all your help and advice. And no, it wasn't the flux capacitor in the end.

    When you say "Flowing freely in my parents house", I assume you mean as and when it is required, and not...you know...flowing freely! :twisted:
  • Well done mate,
  • I know this was q few years ago but I've got the same problem and had 8 people look at it and no fix. Did you get a fix? If so what ?
  • Wow. That was a long time ago. How ever did you find this thread ?

    I ended up just replacing the old taps with new ones, and everything worked OK after that.
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  • AnonymousAnonymous Posts: 28,799
    diplodicus wrote:
    From what you have described sounds like it is a split in the diaphragm washer. When they split it takes a higher flow rate to activate the boiler hence why your bath hot tap works but not the others.

    Hope this helps. By the way i am a heating engineer so not just guessing :D

    Er, he had zero flow from the two taps, so how does that work?
    Can I have your number so I know who not to call should I have a plumbing problem :D
  • diplodicus wrote:
    If he has no flow then my earlier post is not the answer. However more often than not when customers say no hot water out of a tap they mean they have water flow but not hot. Rereading it does look likely that in this case it is no flow :oops:

    OP have you any water at all coming out of the basin and kitchen sink tap?


    As you can see I read the first post wrong..

    But nice "cheap shot" carbonator. Carry on :roll:
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