Both pipes feeding new shower mixer are cold.

[DIYlife]

Hi - I’v just installed a new shower mixer valve in my en suite bathroom but it was only running cold water. I initially thought the mixer was faulty but after checking both feeds I realised they are both cold. The basin tap runs hot and so does the shower mixer and basin in the main bathroom.

No pipe work has been changed so I’m baffled as to why both these feeds are now cold. The only thing I’ve had done recently is a new boiler install converting from a gravity fed to a combi system.

Can anyone advise on what could be the issue?- any help would be very much appreciated.

Regards

 

[terryplumb]

What type of shower valve have you installed ?
Has it been installed on original pipework ,that previously worked fine with a mixer ?
Has any pipework been altered since your original shower was in use ?

 

[jeff the gasman]

Probably an air lock

 

[DIYlife]

Yes it has been installed on the original pipework that previously worked fine with old mixer. New shower mixer is a Cruze.

The only work that’s been done is the conversion from gravity fed system to condensing combi. All other hot water outlets work okay though.

Regards

 

[DIYlife]

I thought maybe an air lock but I’ve had both feeds running for a couple of minutes with no change. Plenty of pressure on both of them.
As soon as I open another hot water tap I hear the boiler fire.

 

[Deleted member 267285]

Does the boiler fire up for hot water when the shower is ran?

 

[DIYlife]

It does when the main shower is ran but not the new mixer in the en suite

 

[Deleted member 267285]

Are you able to isolate the cold feed under the boiler?

 

[DIYlife]

The boiler has a cold feed isolation tap yes.

 

[terryplumb]

Close it ,and see if water still flows from the " hot " pipe that supply's the shower valve. Preferably with the shower valve removed.

 

[DIYlife]

Okay I will give that a try thanks.

 

[DIYlife]

I have isolated the cold feed to the boiler and still have water coming out of both pipes that feed the mixer. All other hot water outlets are off as expected.

So it looks like both pipes are now cold mains fed - I can’t understand how this can happen really as surely all the HW outlets are fed off the same pipe from the boiler?

 

[ETAF]

when they changed the boiler , did they remove all old tank amd modify all the pipework for the hotwater
We had a cimbi added a few weeks ago, and all the old tank and pipework removed and capped, in the loft

perhaps the shower had a seperate hot feed from the loft or where ever the tank used to be, and they connected to mains somehow , strange thing to do....

MIXER
is this a shower off a set of taps ?
if so does the hot run OK from the TAP

 

[DIYlife]

Yes they changed the pipe work - I have a main bathroom which has a shower and basin (all working) another en suite with shower and basin (all working) but in this en suite only the basin is getting the hot feed.

The new shower mixer is a single unit which is cold both sides when connected.

The old tank and cylinder has been removed yes. I just can’t understand how this one outlet seems to be connected to the cold feed. It’s a 2005 build house and I would have thought all the HW feeds were coming the same way.

 

[terryplumb]

Yes it has been installed on the original pipework that previously worked fine with old mixer.

I assume you didn't use the old mixer after the combi was fitted / gravity conversion ???
You need to get the plumber back ,as pipework has been done incorrectly upstream of the shower valve.