what's this for..... mixer shower flow issue

[ja5599]

Hello,
Can anyone advise? No cold coming to my shower (since combi install).

Have adjusted everything I can see/reach/adjust but nothing working.
The thermostatic mixer has these two screws on each water feed (see picture).

Can anyone tell me what they adjust? The one I can turn seems to make no difference to flow, temp or anything. The other has a kncekered head- before I begin taking it apart, would nbe good to know what this is.

I am a bit out of my depth, but would appreciate any help or advice.

THanks
J

 

[danielp]

is the cold still fed from the tank

 

[Bernie2]

Danielp is right.

The hot will be at the new combi mains pressure the cold still at the old tank pressure probably.

 

[ja5599]

thanks daniel, bernie
but how can i tell if its the tank or the mains?

 

[Bernie2]

Please remember we are guessing a bit here, as we don't know what sort of system you had in before you got the combi.

Its only a suggestion that the shower cold was tank (cistern) fed from the loft and the shower hot was fed from a hot water cylinder, which was fed from the same tank in the loft as the cold for the shower.

If that is the case, then we suspect that when the combi was fitted the cold supply to the shower was not reinstated off the same mains pressure pipe as the new hot supply from the combi, giving both shower supplies near enough equal pressure.

If the cold shower supply is still fed from a tank in the loft, then it will probably be at a far lower pressure than the hot. In effect the hot is possibly forcing the cold away from the shower and back toward the tank in the loft.

The thing is, we don't even know if you have a tank in the loft and if you have whether its still got a water supply to it.

Did for instance, the combi installer go into the loft and link the old cold mains tank water supply to the cold shower supply?

If there is a tank and it is empty, then they may very well have forgotten to link your shower back up to the mains water.

If its full then the cold may very well be at a much lower pressure than the hot.

To try that theory:

Turn the combi off electrically, then turn the cold water supply off to the combi hot water, its usually a tap under the combi. Once the hot is off the cold should come out of the shower.

If it doesn't then you would have to investigate further where the shower cold feed comes from. If its from a tank, then easiest way probably is to connect it up to the mains water supply, to give you near enough equal hot and cold pressure to the shower.

Don't forget to check your shower can take mains pressure and you have installed nrvs as required by the water regs. And turn the water back on to the combi as well as the electrics.

Object is to make sure the shower is getting a balanced pressure from both the hot and cold water supplies. And checking to see if shower is suitable for mains water pressure

 

[ja5599]

Thanks again Bernie. YOur guess at my system is pretty spot on. I have a full tank in the loft. My boiler fitter said this was now redundant (even though still full). Wehn the boiler is off, the cold water pressure in the shower is fine.

Does this suggest my boiler fitter is not being 100% truthful? I have spoken to him about this and he suggested it was my mixer. It worked fine before the boiler, and inspecting it and cleaning it, all looks ok (to my eye).


I think I will have to call another plumber - wasn't sure until you responded whether it was a job big enough for someone to take bother with.

Thanks again,
J

 

[stevetheplumber]

what color was the last plumbers horse ?

 

[ja5599]

don't get it

yes i do, but slowly

john wayne right?