Hi
Hot water turned yellow after I turned the mane valve off to replace an old tap. There is no low pressure or any other sign of airlock and cold water is of a normal quality but hot water looks dirty and fills like it has some particles in it.
What the issue could be?
And how it can be fixed?

How often do you flush your heater? If the answer's never then you've found the problem. You should always flush, not drain, your heater on a regular schedule to get rid of mineral buildup. Let me show you how.



For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule.

Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run untill the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes.

Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back together the same way you took them out. Don't forget to flush it out every month. Your heater will thank you for it. Hope this helps and thank you for rating my answer,

Tom