Hot water system - noise and not enough hot water

highwalker

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?

Ebe_Scrooge

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 ).

Loanranger

Bleed the radiators then see how it is.

highwalker

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

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

@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

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

highwalker wrote: »

@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

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

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

Could be air lock trapped in the system. I normally check mine at the time of year getting them ready for winter.

southcoastrgi

Google thermal store cause that’s what you have it’s not a combi