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    • highwalker
    • By highwalker 3rd Oct 17, 2:59 PM
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    highwalker
    Hot water system - noise and not enough hot water
    • #1
    • 3rd Oct 17, 2:59 PM
    Hot water system - noise and not enough hot water 3rd Oct 17 at 2:59 PM
    We have a combi system using a BoilerMate 2 on the upper floor that was working well until a couple of weeks ago. The only thing that changed was temporarily shutting off the water in order to repair a leak in some hot water sink piping downstairs.

    1) Initially, the problem was that when running the bath, you got about an inch of hot water before the tap went lukewarm. The boiler didn't fire up until you ran another tap hard for a little while and then you could see that it did fire up.
    2) Most recently, the system has now started making major loud cavitation-type noises associated with the use of hot water: a massive gurgling sound a bit like air bubbles suddenly breaking through some blockage in the water, followed by a long running water sound.

    Any thoughts?: online research suggests that cavitation can be associated with too low pump suction pressure, but what would have changed that?
Page 1
    • Ebe Scrooge
    • By Ebe Scrooge 3rd Oct 17, 3:53 PM
    • 3,928 Posts
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    Ebe Scrooge
    • #2
    • 3rd Oct 17, 3:53 PM
    • #2
    • 3rd Oct 17, 3:53 PM
    Have you bled the system ? Air in the system would be one possibility - especially if you say you've recently had to repair a leak. Try bleeding the whole system - at least it's easy to do and will cost you nowt.


    Also, check that the system is pressurised to the correct pressure ( the manual will tell you what the correct pressure should be, or else it's often marked on the pressure gauge itself ).
    I may not know much about art, but I know what I like.
    • Loanranger
    • By Loanranger 3rd Oct 17, 3:58 PM
    • 1,976 Posts
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    Loanranger
    • #3
    • 3rd Oct 17, 3:58 PM
    • #3
    • 3rd Oct 17, 3:58 PM
    Bleed the radiators then see how it is.
    • highwalker
    • By highwalker 4th Oct 17, 10:31 AM
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    highwalker
    • #4
    • 4th Oct 17, 10:31 AM
    Radiators OK, but problem still there
    • #4
    • 4th Oct 17, 10:31 AM
    Bled the radiators - very little air (and central heating not on yet) Problem still persists. Pump seems to be inbuilt - if there is a pressure reading, it would be behind inspection panel
    • Le_Kirk
    • By Le_Kirk 4th Oct 17, 11:56 AM
    • 2,146 Posts
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    Le_Kirk
    • #5
    • 4th Oct 17, 11:56 AM
    • #5
    • 4th Oct 17, 11:56 AM
    Where did you shut off the water? Main stopcock? Are you sure you turned it back on fully or could it be stuck in the partially closed position? Is it a gate valve or a ball valve? If it is a combi, it won't be to do with the heating as that is a separate system.
    • highwalker
    • By highwalker 4th Oct 17, 1:56 PM
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    highwalker
    • #6
    • 4th Oct 17, 1:56 PM
    • #6
    • 4th Oct 17, 1:56 PM
    @Le_Kirk - following advice re: radiators above - I wasn't sure that it could be central heating as it was the hot water was providing the problem (and the system is combi-like), but the Boilermate does use the CH to heat the hot water store in the Boilermate. If I drain whole system, would probably start with feed into the Boilermate, as main stopcock below the kitchen sink is a little tricky
    • ComicGeek
    • By ComicGeek 4th Oct 17, 2:30 PM
    • 213 Posts
    • 154 Thanks
    ComicGeek
    • #7
    • 4th Oct 17, 2:30 PM
    • #7
    • 4th Oct 17, 2:30 PM
    I've had Boilermates in the past, but have been quick to replace them. Some seem to work really well, and others need constant attention....

    It's the reverse to a standard hot water cylinder and system boiler, with the central heating water within the tank and the hot water feed run through the cylinder coil to generate hot water instantaneously. As a result the cylinder coil can get really clogged in a hard water area - temporarily shutting off the water to the coil can then sometimes cause further blockages as debris comes loose. You can also get trapped air in the top of the coil as well, which could explain the noise. The clogging of the coil also affects heat transfer, so can reduce water temperature apart from the small amount that has had more time to heat up while sat in the coil.

    I would get it drained and then look at the coil.
    • Le_Kirk
    • By Le_Kirk 4th Oct 17, 3:58 PM
    • 2,146 Posts
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    Le_Kirk
    • #8
    • 4th Oct 17, 3:58 PM
    • #8
    • 4th Oct 17, 3:58 PM
    @Le_Kirk - following advice re: radiators above - I wasn't sure that it could be central heating as it was the hot water was providing the problem (and the system is combi-like), but the Boilermate does use the CH to heat the hot water store in the Boilermate. If I drain whole system, would probably start with feed into the Boilermate, as main stopcock below the kitchen sink is a little tricky
    Originally posted by highwalker
    Aha, didn't know it was set up like that. However, I would start with wherever you turned off the water (as per your OP).
    • Alex1983
    • By Alex1983 4th Oct 17, 5:51 PM
    • 520 Posts
    • 294 Thanks
    Alex1983
    • #9
    • 4th Oct 17, 5:51 PM
    • #9
    • 4th Oct 17, 5:51 PM
    I agree with comicgeek, boiler mates are rubbish. Do you have a pressurised system or do you have a header tank in the loft.
    • Phil&Michelle
    • By Phil&Michelle 4th Oct 17, 6:02 PM
    • 74 Posts
    • 43 Thanks
    Phil&Michelle
    Could be air lock trapped in the system. I normally check mine at the time of year getting them ready for winter.
    • southcoastrgi
    • By southcoastrgi 5th Oct 17, 8:50 PM
    • 5,218 Posts
    • 3,035 Thanks
    southcoastrgi
    Google thermal store cause that’s what you have it’s not a combi
    I'm only here while I wait for Corrie to start.

    You get no BS from me & if I think you are wrong I WILL tell you.
    • highwalker
    • By highwalker 5th Oct 17, 9:09 PM
    • 5 Posts
    • 0 Thanks
    highwalker
    Investigation last night managed to reveal that the expansion vessel on top of the thermal store was out of water: so, either the inlet was blocked up (seems unlikely at mains pressure), or the ball valve inside it has got a problem - e.g. grit in it. This could explain some air getting in as the expansion emptied. Topped it up manually to see what would happen - water still in there. However, noise events still present, if perhaps sounding fractionally less harsh.
    • Alex1983
    • By Alex1983 6th Oct 17, 10:51 PM
    • 520 Posts
    • 294 Thanks
    Alex1983
    It’s quite common for the cold feed from the header tank on top of the boiler mate to block, if your header was empty, I wonder if there is airing in the top of the store and it can’t refill because the cold feed is blocked.
    • highwalker
    • By highwalker 7th Oct 17, 8:25 AM
    • 5 Posts
    • 0 Thanks
    highwalker
    Thanks. Conclusion is now that the feed from the expansion tank to the thermal store was blocked, but more importantly the circulation pump had/was dying. This led to cavitation in the boiler that resonated upwards plus variable temperature hot.. Pump now replaced and all running quiet so far.
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