Overflow problem

[amanda pearson]

I am having a problem with my central heating.I have an old boiler which heats the water and stores it in the cylinder.I recently had a new shower and taps so all the water was turned off.When we turned it back on,after a week or so,the overflow started running,but stopped when i ran the hot water.We checked the ballcock in the hot water tank and expansion tank both of which were fine.Also the radiators upstairs are boiling hot and it takes about an hour for the downstairs ones to get hot.
I had a new radiator about a year ago and the plumber who fitted it said he was having a problem with the valve that switches from central heating to hot water.Could this cause the problem? Any help appreciated.
It's definately not the ballcocks,I have checked.Also turned off cold supply to mixer shower but it still overflows.whatever is happening takes two hours for the overflow to start.Radiator problem started at the same time.Black bits come through hot tap into bath and the hot water pressure is not as good as before the new shower and taps

 

[prs1]

your radiators could need balancing ie the lock shield valves need adjusting to ensure an even flow around your system.Water always tends to take the shortest route hense some rads being hotter than others!
And as for your dcw tank it shounds like you ball valve is passing slightly
Replace the ball valve and see if this cures the problem.
Both simple jobs to do !

 

[Bernie2]

Hmm!

Check the water level in the store tank is not to high.
Also check thermostats both on any immersion heaters and the dhw cylinder. It may be that a temperature control is faulty somewhere. It's highly dangerous for hot water to be flowing back into a stored water tank especially if its plastic.

When a cylinder gets hot, the water partly expands up the cold feed into the stored water tank but it should only get warm not hot. So if you feel the cold water pipe going into the cylinder getting hot, look around for the cause of the water over heating. Also check for any dhw air locks.

The cause of your radiator problem, without knowing the system, is mostly likely pump, control valve, air or sludge related, balancing the valves will also help.

 

[stevetheplumber]

if either of the showers or mixers are mains fed it could be those causing the overflow downstairs cloakrooms are often mains fed

 

[WHPES]

Sounds to me like uneven hot / cold pressures to a mixer. Are any of your shower / mixer taps fed from unuequal pressures (i.e. does the rising main feed the cold to any of them?)

If so then it's probably a faulty non-return valve and possibly a plumbing error.