Hot cold cross over

[sycamore]

Hi
I recently installed a new mixer tap, after a few days i could hear water running and my hot water was cold so i investigated and found the cold was leaking through the tap into my hot line. I know i can fit a non return in line but should i be doing this? Surely the tap is faulty and not fit for use as they do not make them to pass by. Unfortunatley the company i brought it from are saying there is nothing wrong just fit a non return.
is the tap faulty or not?

Regards

 

[lame plumber]

depends if the tap is low pressure use and you have it on a high pressure cold main, fit non return valves to resolve the problem

 

[sycamore]

ok will check on the tap thanks for reply

 

[Best]

If the tap is fully turned off and the mains water is passing through the body and into the hot, then the tap is faulty. A pin hole or tiny crack between the waterways in the body will do that. On these single block taps especially it can happen.
Tell your supplier that they are talking rubbish & they have sold you a faulty tap. A non return valve on the hot should stop the water passing, but this is normally only for when the tap is actually turned on. Ask your supplier to explain how it is okay for a tap that is turned fully off to have both waters mixing?