reducing water pressure in worcester bosch combi boiler

humey53 · Posted: Sat Mar 26, 2011 8:39 pm

Visited my mum today and noticed the pressure dial on her Worcester Bosch boiler was reading 3.5 bar, which seems higher than I thought was recommended. I happen to have the same boiler, so am interested to know

1 how do you reduce the pressure (I know how to increase it)?

2 Does it incurr any damage running at this higher pressure?

3 Isn't 1 bar the correct pressure?

powerflushingpro · Posted: Sat Mar 26, 2011 8:57 pm

It's not good. Make sure the filling loop is shut, then bleed a radiator to reduce the pressure it will take a while to get it to between 1-1.5bar. If the pressure goes back up you need a professional to have a look at it.

Bankrupt · Posted: Sat Mar 26, 2011 11:26 pm

Certainly too high - Is it reading 3.5 Bar with the pump running or not running ? Is the key removed from the filling loop ? - If not you may have pressurisation from the mains water supply via the filling loop.

hansthebear · Posted: Sun Mar 27, 2011 12:25 am

points to a faulty pressure relief valve also

bengasman · Posted: Sun Mar 27, 2011 10:56 am

When was the last time the boiler had a full service?

Bankrupt · Posted: Sun Mar 27, 2011 6:10 pm

bengasman wrote:

When was the last time the boiler had a full service?

Why would lack of servicing cause the pressure to be too high ? .

Are you suggesting that lack of inhibitor could be causing corrosion and the hydrogen formed is increasing the pressure ?

rgas · Posted: Sun Mar 27, 2011 9:13 pm

Likely to be the expansion vessel or loop left on, turn the heating off and let the system cool, does the pressure drop? If so its your vessel, if not and theres a constant drip from the blowoff, its your loop or possibally the heat exchanger split depending what type it is. Ive never had hydrogen causing problems with pressure, would normally release itself through the auto air vent. He was asking about servicing as we normally check expansion when we service it.