Hot water tap cold after new bath install

yolo1988

After some advice...new bath installed and the hot water tap is coming out cold/lukewarm. Plumber did comment that our water pressure was really high (new build) and the water was firing out of the taps so I wondered if the flow was too fast for our combi boiler to heat, so we ran it slowly and still it would not heat. Plumber is coming back but not till Thursday so wondered if anyone might know what is causing it? Or if we could sort it ourselves? Would really appreciate the advice thanks. 
P.s we have also checked the plumber wired the taps wrong and the cold tap is definitely cold 🤣

jonnydeppiwish!

Probably a silly question but is there hot water coming from other taps? Has the boiler been switched off or the temperature turned down?

plumb1_2

Is there a tmv3 valve under the bath

tacpot12

The plumber might have upgraded some pipework, or inadvertently removed a restriction in the previous supply to the hot tap (or the new taps might have better flow rates), so that the flow through the combi boiler is too great. If this is the case, I think some taps can have a flow restrictor fitted, but you can also get a pressure reducer installed at the point where the water enters the property, and I think I would do this if the pressure is above 4 bar. 

But if this is the problem, your boiler should fire and try to heat the water if the hot tap is opened. With the boiler running, you should be able to turn the tap off slowly to the point where the boiler can heat the flow through the tap. If the boiler doesn't fire when you open that tap, but does when you open other taps, I would talk to the boiler manufacturer to find out what is causing this.  

yolo1988

jonnydeppiwish! said:

Probably a silly question but is there hot water coming from other taps? Has the boiler been switched off or the temperature turned down?

Hi, yes hot water is coming from the other taps so it is really strange. The boiler hasn't been touched either  

yolo1988

plumb1_2 said:

Is there a tmv3 valve under the bath

No idea. We don't want to break the sealant around the bath panel to look just in case the installer thinks we might have fiddled with something. Thanks 

yolo1988

tacpot12 said:

The plumber might have upgraded some pipework, or inadvertently removed a restriction in the previous supply to the hot tap (or the new taps might have better flow rates), so that the flow through the combi boiler is too great. If this is the case, I think some taps can have a flow restrictor fitted, but you can also get a pressure reducer installed at the point where the water enters the property, and I think I would do this if the pressure is above 4 bar. 

But if this is the problem, your boiler should fire and try to heat the water if the hot tap is opened. With the boiler running, you should be able to turn the tap off slowly to the point where the boiler can heat the flow through the tap. If the boiler doesn't fire when you open that tap, but does when you open other taps, I would talk to the boiler manufacturer to find out what is causing this.  

The only thing I remember him saying was that the new mixer taps we had bought struggled with the pressure of the water being so strong, so he said he had turned the water pressure down but it is still really really powerful and fires out the tap! We are wondering if it might be the tap causing an issue but your comments make a lot of sense in regard to pressure/flow. I really hope it is a sortable fix...I want a bath 😅

Mr.Generous

Im wondering if a cold feed has been connected to the hot feed under the bath somehow so the  high pressure cold is bleeding over the hot when you open the tap. A puzzle as to why but ...

Gavin83

Mr.Generous said:

Im wondering if a cold feed has been connected to the hot feed under the bath somehow so the  high pressure cold is bleeding over the hot when you open the tap. A puzzle as to why but ...

If it’s a combi boiler then the hot water should be at mains pressure.

I suspect there might be a tmv fitted and he’s forgotten to adjust it to a reasonable temperature.