Combi boiler sounds like a steam train!!

ferry

Hi all
Looking for some advice here please.Another boiler question I'm afraid.

After flushing the upstairs loo my combi boiler sounds like a steam train until the cistern is finished filling up.
I'm assuming it's boiler related?

Any ideas if this is a problem as I'm due a BG engineer on the 25th and could highlight this.

Thanks a lot
Terry

moneysavingplumber

It sounds like 'water bounce' where the action in the water main when the loo is flushed is interfering with the boiler flow switch. It's usually remedied by installing a double-check valve followed by a mini expansion vessel on the water main. It may just be a loose jumper vibrating in the stopcock that happens to be near your boiler, the boiler would usually fire if it was being affected, but the same action will remedy this also.