Shower mixer valve problems

[Mridley81]

My shower mixer valve isn't working correctly. When you turn the shower on, no water water comes out. But if you turn the temperature up to maximum, the shower works but is too hot to use. The strange thing is only this only happens sometimes. Sometimes the shower works perfectly. All the other taps work fine in the house and the pipes running to the shower both have water running through them. The mixer valve is brand new as I replaced the old one because of a similar problem. That mixer valve wouldn't go hotter than luke warm, no matter how far you turned the temperature up. Any advice would be great.

 

[Newboy]

check that H&C connections are to the correct shower inlets

 

[Mridley81]

I'm confident this is installed correctly any other ideas? As I say sometimes it works perfectly.

 

[JohnD]

why don't you want to check?

You can post a photo if you like, and tell us which side the hot pipe goes into.

 

[picasso]

Sticking cold non return valve.

 

[fred1981]

what kind of shower is it?? is it thermostatic, is it an exposed valve? is it pumped ot gravity or off a combi boiler... could be a lot of things.

 

[TeaTime]

Possibility that the filters need cleaning? If all you have done is change the thermostatic cartridge when you 'fixed' the valve last time, there is a chance that the inlets are having flow restrictions due to clogged filters.

Alternatively the NRV might be sticking. Give it a blow through to check.

Finally, are you sure you fully opened the water inlet, when you put the water back on to the shower supply?

 

[longdogs]

If its a bar shower, sometimes the valve spindle unscrews inside, which can cause intermittent problems. Check to see if the valve is operating properly by removing the valve and screwing/unscrewing by hand. Also gunge inside the valve can cause similar problems.