Water pressure valve ?

Collibosher

This valve was installed after an attic conversion, and runs off the mains water supply to tank.

After the valve it appears to run into the heating system.

The red marker on the dial is set at 2bar, but needle is showing at 2.5bar.

Could someone tell me what the purpose of this is, and is it something that should be looked at.

K.Flyer

It's called an automatic filling valve and its for keeping your central heating system topped up with pressure.
Most good installers do not like or use them as they can mask minor leaks in your heating system which should really be found and repaired.
The red pointer is irrelevant, its just used as a reference point.
The black pointer is the one indicating system pressure.
Yours has been set a bit high, the normal set point would be approx 1.25 - 1.5 bar.

Collibosher

Thanks, most helpful

The control underneath it is turned fully clockwise, so I presume this is for the flow of water into it ?

If there's air in the rads, does this valve let in more water as they are bled ?

K.Flyer

If the black knob is fully clockwise, it is in the closed position, which I believe is the best place to leave it after you have refilled and vented radiators.
The small threaded bar at the other end adjusts the pressure setting, I would back this off a little following the plus - minus marks on the body to reduce the pressure.

Collibosher

That's great, thanks for your advice

pumpit2010

My pressure gauge keeps dropping back to nearly zero within a short time of opening it up to bring the pressure up to 1.

is it dangerous to turn the heating on (just to heat water) while the pressure is so low?

also another quick question. What is the red cylinder for? It has a valve similar to a car tyre?

K.Flyer

pumpit2010 wrote: »

My pressure gauge keeps dropping back to nearly zero within a short time of opening it up to bring the pressure up to 1.

This is a sign that you are loosing water either through a leak or out through the safety valve if there is no pre-charged air pressure in the expansion vessel.

is it dangerous to turn the heating on (just to heat water) while the pressure is so low?

It would be best to have the water loss rectified as soon as possible because you are slowly doing damage to the boiler and your heating system by constantly introducing fresh water.

also another quick question. What is the red cylinder for? It has a valve similar to a car tyre?

That is an expansion vessel. As your system heats up it absorbs the increase of the heating system pressure.
It should have a certain amount of air in it, otherwise problems can occur with the heating system. (See above)

pumpit2010

Thanks k.flyer

Is it a big job to get this fixed?

K.Flyer

If it is a case of no air in the vessel and a leaking safety valve, then its usually not too big a deal.
If the vessel needs to be changed, which can cause the same problem, then it still can be straight forward enough.
But if its a leaking pipe somewhere unknown, then its "How Long Is A Piece of String" unfortunately.