Reducing water pressure on a Vaillant 837 boiler?

njhpuk

Hi,
I've got a new boiler and I've overfilled it (it wasn't coming on and I thought it was a lack of pressure - I was wrong, it was something else) so when the central heating is turned on the meter is going into the red. How do I slacken off the pressure?
Cheers.

Canucklehead

Hi.

Either a radiator vent or drain off under boiler. They are on/near c/h flow and return isolation valves. See manual for location.

GSR.

njhpuk

Thanks for your reply. I'm a complete newbie to this...is it a matter of turning a switch or do I need to attach a hose and siphon water out?

TwoEnigmas

Your radiators will all have bleed valves - little screws on the tops, with a nearby hole to let out air/water.

Get a glass/cup, and go round each radiator. Loosen off the screw, wait until any air comes out and it starts spraying water. Turn off.

If the pressure is still too high once you've bled all the radiators, drain off some more water from any radiator - only about a cupful at a time. You'll be surprised how little water makes the pressure gauge go down.

gas4you

On each of the ch isolation valves under the boiler are brass drain points.

Use a 7mm open ended spanner or a small adjustable to open it, with a bowl under it first of course.

Do it with the boiler cold so you don't scald yourself with hot system water.