Increasing pressure in a combi system.?

Question

We have a Valliant combi boiler that is running at around 1.5 bar. I want to increase the pressure to 3.0 bar, but the boiler won't maintain the pressure.

After filling the system and closing the valve, it only takes around an hour for the pressure to drop back to 1.5 bar.

Is there something wrong, or is it just not possible to increase the pressure? We bought a spa bath that requires a minimum of 3 bar pressure, which is the reason for the need to increase.

Thanks.

Answer 1

I agree with the other 2 posters, but just to let you know, the reason the combi pressure won't stay at 3 bar after you have adjusted it is because 3 bar is prescisely the pressure at which the Pressure Relief Valve (PRV) blows & sends water out side via a kind of overflow pipe.  

Answer 2

You have got the wrong end of the stick. The boiler pressure that you can adjust affects only the water in the radiators. 1.5 bar is about right and is the design pressure. The boiler is venting the excess water when hot to reduce the pressure to what it should be.

The pressure at your taps is dictated by the water company! It is the cold water feed to your property that passes through the combi that arrives hot at your taps. You need to connect a water pressure gauge on a mains tap e.g. your outside hose tap, to find out what the figure is. You can also ask the water company what the figure is for your postcode. They aren't always right, which is why I bought a gauge! (At a Plumber's Merchant's)

Answer 3

The your boiler pressure is a separate system to the hot water supply to your taps. Increasing this pressure will not help you.

You need to check the pressure at you taps this is the mains supply pressure at your stop ****; that is unless you have a pressure regulator fitted after the stop ****.