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Central Heating Vent Pipe Overflowing Using Ideal Wix Boiler

Postby adrwilliams » Wed Nov 28, 2018 2:27 pm


Ive read several posts on this but none quite seem to fit.

Can anyone advise?



Ideal Wlx boiler (1985 and going strong)

Fortic tank (combination tank) in loft

Vent and fill pipe in correct position just before pump.

F+E tank and larger fortic tank header at a similar height.

No problems for 12 years, then 8 months ago, vent pipe starts overflowing so I turned pump down from 3 to 2. Perfect.

this last week, its started again. I've turned it down to 1 and that's stopped the overflowing vent pipe (for now!) but CH is now suffering.

It does this even when the system is cold and the heating off. Boiler is switched off and completely cold right now and I've just turned the pump on. As soon as I turn pump up to 2/3 it starts cold CH water flowing into the F+E tank.

Ive let it flow for a good while and the water level in the FOrtic tank header hasnt changed, so the HW cylinder doesnt appear to be losing water into the coil?

My thoughts:

Silt in CH system - requires flushing?

Any other thoughts or suggestions?

Thanks in advance!

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