Can someone help me please?!

[Claz21]

Could some kind soul please help me as this is driving me mad.

Full disclosure im an amateur DIY'er. So about a week or so ago the over flow outside my house started dripping and then pouring. I checked the cold water storage tank in the loft and it was over flowing. I found it was filling up from the bottom, and not the bullcock valve. So after a bit of internet investigation i concluded that the problem was probably a leak in the coil within my hot water cylinder. It was very old so seemed plausible.

So i bought a new one on Screwfix and was able to change it over without too much fuss. I was actually very pleased with myself. However to my despair this has not solved anything. The water is still overflowing in the cold water tank when i turn the hot water on. Can anyone advise me what it could be? Could it be the new cylinder is faulty? Or is there something else? I have also replaced the cylinder thermostat with a brand new one. Any advice would be gratefully received. Thanks.

 

[ShaunCorbs]

Have you changed any taps recently?

 

[snowhead]

What taps have you got around the house, any thermostatic mixers?

It's probably crossing mains pressure Cold into the Hot, then pushing water out the cylinder back up into the tank.
It would have to be a mixer tap with Hot and mains pressure Cold that's causing the problem.

 

[Riley]

Mixer

 

[king of pipes]

As above snowhead is probably right the mains cold water pressure is alot higher than the hotwater supply somehow it's pushing up the hot water supply pipework into the cold water storage tank causing it to overflow , either through a mixer tap ? or shower valve ? Kop

 

[Claz21]

Interesting...every tap in my house is a mixer tap. Plus the shower. Is there a clever technique i can use to identify the right one? Thanks in advance all.

 

[king of pipes]

If you can isolate each one individually then yes if not then it's a process of elimination Which is a bit tricky

 

[Chuck]

Run some hot water through the mixer-under-suspicion until the supply pipe gets warm and then shut off the flow. Monitor the temperature of the supply pipe for a minute or two. The hot supply to the mixer that's leaking cold will cool much more rapidly than one where there is no crossflow.

You can skip any mixers that have separate hot and cold valves. Test any that use a thermostatic method to control the temperature.

 

[Phil]

Listen to each one with your ear against it, or a large scewdriver between the mixer and your ear. You will hear one with a hiss.

 

[Claz21]

Listen to each one with your ear against it, or a large scewdriver between the mixer and your ear. You will hear one with a hiss.

Mate can't thank you enough! Think I've found it and its the shower.