sounds like an expansion problem.

[moogwai]

Hi guys,
just had this enquiry come through my website...
"Every night the boiler starts banging and the pressure is all over the place, with water pouring out of the overflow pipe outside. The only way i have found to stop this is to turn the boiler off and release the pressure in the boiler but it can start all over again when you switch it back on. Could you give me a quote on sorting this problem out please"

waiting for details on boiler but i'm thinking expansion vessel could be knackered or filling loop is passing. Not been to job yet just wanted your first impressions.

 

[Puddle]

could be the filling loop passing or plate heat exchanger with small split,as water pressure increases at night due to lack of use in area,so pressure creeps up n boiler

Or maybe property built on old nunnery and something more sinister is happening

 

[moogwai]

ahh yes....never thought about that one.....it's a baxi combi by the way,didn't say whether his house was built on a old nunnery so i'm ruling out any dead nun tomfoolery!

 

[WHPES]

Faulty boiler thermostat?