Plumbing Question

Why does my combi boiler ignite when i run the cold tap?

I have a Halstead CBX 320 combi boiler that has been serviced annually for the last three years. In the last year I have noticed that the boiler sometimes starts up (ignites) for a few seconds when a cold tap is run? Whilst the plumber that serviced the boiler said that 'this sometimes happens' he offered no solution. Whilst I am content it is not a safety issue, it is pretty annoying; not to mention a waste of very expensive gas! Can an expert shed some light on this issue.

3 Answers

Best Answer

hi, have seen this problem before and it is usually to do with cold water pressure. pressure builds up in pipework and gets released when tap is opened. have water pressure checked and have pressure reducing valve fitted if required. hope this is helpful adrian

Answered 8th Oct 2011


Member since 28 Jun 2008

Its often to do with pressure fluctuations
Fitting a non return valve to the cold main by the boiler normally cures it


Answered 12th Oct 2011

Lambert Plumbing & Heating Ltd

Member since 11 Oct 2011

It's worth having the pressure differential checked to see what is making the microswitch operate. The solution may be quite ample.

Answered 12th Oct 2011


Member since 11 Oct 2011

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