Hot water venting cold water header tank

[ANGLER]

Increasing issues. Hot water from the emersion tank venting into the cold water tank, causing the water to level to reach the overflow.
Hot water only used for kitchen and bathroom

 

[Daveydub]

Is your heating tank fed or sealed system?

 

[ANGLER]

The tank is a indirect tank. The tanks are only used for kitchen and bathroom tap use.

We have electric storage heating system.

 

[Daveydub]

The tank is a indirect tank.

So nothing is connected to the coil in the cylinder?

 

[oldbuffer]

Assuming the hot water is heated only by the immersion heater (not by a boiler) then, if the hot water is extremely hot, the thermostat in the immersion heater may have failed, allowing the water to heat up too much. It then expands into the cold water storage cistern (CWSC), and will cause it to overflow.

If it is this, then it needs fixing as a matter of urgency, or the CWSC could collapse and pour very hot water through the ceiling.

 

[ANGLER]

Last night I replaced the Immersion element & thermostat.
Yet again warm water was being expelled out the overflow on the cold water header tank.

 

[terryplumb]

There is a vent pipe that comes up and over the top of the tank ,and points down Into the tank ,is that where you have seen water coming from ? That's unlikely if you have just replaced the immersion element AND a new thermostat. Are you sure its not the float valve allowing water Into the tank when it shouldn't.?

 

[Daveydub]

So nothing is connected to the coil in the cylinder?

 

[terryplumb]

Do you have a mixer valve ,shower or tap ,that is fed cold from the mains. Possible cross flow into gravity hot water system ?

 

[ANGLER]

So nothing is connected to the coil in the cylinder?

Nothing connected to the coil

 

[ANGLER]

There is a vent pipe that comes up and over the top of the tank ,and points down Into the tank ,is that where you have seen water coming from ? That's unlikely if you have just replaced the immersion element AND a new thermostat. Are you sure its not the float valve allowing water Into the tank when it shouldn't.?

Haven't seen water at present emerging from the vent pipe, but the water being expelled outside is warm. Also contents of the cold water tank is also warm. Ball valve also replaced as a precaution.

 

[terryplumb]

Mains cold water is getting into the dhw system if nothing is coming out the vent pipe.

 

[ANGLER]

Do you have a mixer valve ,shower or tap ,that is fed cold from the mains. Possible cross flow into gravity hot water system ?

If this is happening, how can I prevent this?

 

[terryplumb]

Establish where the cross flow is and eradicate . common on single handle lever taps, thermostatic mixer valves on showers ,bath fillers ,etc pumped hot to shower and mains cold to same. Its a process of elimination really.

 

[ANGLER]

Just let everyone know. The issue went away, when we upgraded our bathroom toilet. The previous toilet had an EYE wash attached, with a cold and hot water feed. The cross over must of occurred here.
The toilet and upgrade was not done for this reason.