Hot water from cold tap??? All aspects of plumbing questions and answers, help, tips and information

[gumbo]

Im getting hot water from the cold tap in bathroom and seems to be getting worse and worse. I seem to remember something on the news about this a while ago and that it can be quite dangerous.
Id guess that the cylinder is getting to hot and the excess hot water is travelling back up to the cold water storage tank but what needs doing to fix this?

[chris_on_tour2002]

the problem that you are referring to and that was well documented in the news was caused by a faulty thermostat on the heating cylinder that failed to tell the boiler that the water was hot enough and no further heating was required.

the water in the hot water cylinder got hotter and hotter as it did the pressure inside the cylinder rose, forcing the hot water up the vent pipe and back into the cold water storage tank. as this effectively created volume in the cylinder, cold water from the tank was drawn into the cylinder only to be heated up. got hot, expanded, went up the vent pipe and, now heated up, back into the cold water storage tank. so the process continues until the cold water storage tank fills with piping hot water. as most storage tanks are only made of plastic they buckle under the heat and ultimately fail, spilling the water into the loft space and down into the room below.

if you have any doubts at all the best thing to do is to turn off you hot water by isolating boiler and call in a professional to asses it. don't use the system until you've had it checked out.

the tragedy of the story in the news is that it was such a basic technical fault with a very simple and relatively cheap fix.

[Dave From Leeds]

Try starting your boiler when the hot water is warm rather than hot, then turn the boiler thermostat right down. If you don't hear the burner shut off it could be that your water is being overheated and a new boiler thermostat may be required.

[nitro23456]

if this is the case, turn you electric immersion to your hot water cylinder off immediately.

Probably a faulty stat on that causing it not to turn off when it reaches temp.

[nitro23456]

get up into your loft and see if the water in the cold tank is hot - if it is you need to act before someone gets hurt or is killed.

I dont want to be alarmist, but this really can be very dangerous especially for the poor soul who sleeps in the room below the tank.

Things to test are:
- get in loft and touch water in the cold tank to see if it is hot
- bubbling noises coming from cylinder in airing cupboard indicating water is getting far too hot
- discoloured water from taps
- touch the vent pipe that goes from the top of the cylinder back up to the cold tank. Touch it at the top of the airing cupboard.... it should never be too hot to hold onto to at the top... although warm is acceptable.

If you are getting any of this, do something about it. Kill your heating and immersion immediately.... you shouldnt need heating on this time of year so it wpn't be any great hardship whilst you get it sorted.

As per my previous post and the others, it is likely a faulty stat either on your electric immersion that sits on top of your cylinder (if you have one) or on the heating circuit itself. This is the actual stat on the cylinder that is visible and shouldnt be set any higher than 60 celsius.

If you manage to identify the problem as the immersion you can just swtich this off permanently and still use the heating circuit to provide hot water.

My final advice would be to get it looked at by a pro if you are under any doubt. The fact that you have hot coming out of your cold and that it is getting worse, suggests that this cycle is well established.

[plumbbob]

There may be several possibilities why a cold tap can run warm, but it is essential to examine the header tank to ensure the problem does not lie there. Get into the loft and feel the temperature of the water in the tank. It should be cold or at ambient temperature.

[htg engineer]

Type of system ?
Cold water storage tank feeding bathroom ?

Any work carried out lately ?

htg

[gumbo]

Thanks for the comments, The system consists of a cold water tank, F &E tank, boiler and cylinder.
When i say the problem is getting worse the hot water coming from the cold tank olny lasts for 20 sec at the most, usually it cold within 10 secs or so.
if its just the stat that needs changing im sure i could manage that

[plumbbob]

Probably the reason your cold water is warm for a moment or two is because the cold pipe lies alongside a hot pipe or runs by the side of the boiler, heating pipes or storage tank and the heat is being transferred between the two.

[gumbo]

[quote="plumbbob"]Probably the reason your cold water is warm for a moment or two is because the cold pipe lies alongside a hot pipe or runs by the side of the boiler, heating pipes or storage tank and the heat is being transferred between the two.[/quote]

Sometimes it is very hot rather than warm

[Mac-the-Wrench]

I would agree with what bob said about the pipes being too close together, I've seen that a number of times. It makes sense if the water runs cold after a few seconds. If it were running hot all of the time, that would be a different problem altogether

Mac