How to re-pressurize a gas heating system

mullmick

Hi:
I have a (hopefully) quick question about re-pressurising a gas heating system currently experiencing low water pressure in the system. Apologies if this is a "dumb" question- I am a first time home owner of 25 yr old property.

A little history for possible diagnosis:
When decorating rooms after moving in, we had to remove radiators from the walls to get old wallpaper off. We followed a number of DIY guides on the successful removal and reattachment of the radiators. Although we filled them up again slowly before opening up the system, water pressure overall fell to almost zero... and the gas burner cut out as pressure fell to almost zero.

We got a pumber in who refilled, and rebalanced the system- and explained to us the best way to remove and re-attach radiators going forward (we were doing it "correctly" anyway). He didnt seem to think our radiator removal had been a problem. He also attached automatic vents to the system. However water pressure dropped again upon reattachment another radiator, although the system continued to work fine.

We have been keeping an eye on the water pressure given our history of problems/errors. I noticed in other posts that people have "repressurised" their water system- can advice on how to do this? Do you think it will help as an interim measure to "check" the system? And finally, any advice on how to best avoid this problem when doing further decorating where the radiator has to come off?

Corkey123

Mullmick

There should a pressure gauge close to the boiler. It is likely to be at zero due to the radiator work. Beside the gauge there should be a valve to pressurise the system again, the gauge should be allowed to go up to 1 and a 1/2 bars.

Each time you remove the rad and refill it, it will release the pressure in the system, so you will need to re-pressuise it again. There's no way around ths that I know

Have a look around the boiler for a gauge and value. The gauge may well be in the boilder housing.

mullmick

Many Thanks Martin- I will give this a try this evening!

crosstownk

Every time you let water out of the system air takes its place. When you refill the system with water you must go to each rad and open the bleed valve to let out the air. Then you open the filler valve again. Repeat this process untill only water comes from each radiator. I assume you have identified the filler valve. Fill the system to 1 bar when cold. Every time you bleed the pressure will drop somewhat so keep an eye on the gauge. The system in my house is 17 years old and the gauge is above the boiler in the garage and the filler valve and pressure vessel are in the attic beside the water tank. Be careful not to over-pressurise the system - if you do you can open a radiator bleed valve to relieve some pressure. I'm not a plumber but I've done extensive work to the heating system in my house and I've found that this is the best way to remove air and pressurise the system correctly. Additionally, you will need to ensure that all the radiators are warm in a week or so as small pockets or air in the system now will gather with time - it may take several weeks/months to erradicate all of it. My system took about 6 weeks but its been perfect for the last 4 months. Best of luck.

joemc99

On topic, so I'll use this post!

Right, need to remove rad upstairs and move to different wall. This involves cutting back the pipes. Problem is, I am unable to locate the flush cock anywhere? There is one at the bottom of the hotpress (upstairs), but surely this is not it!

All indications point to a sealed system, pressure vessel, pressure valve, etc. Can I remove the rad as normal, shutoff water to the CH system, and relieve the pressure from the rad valve? Then I can cut the pipes back and not too much water will come out?

I have seen on some sites that a sealed system should only be touched by a pro as refilling is a problem! Any advice would be great!

jabaroon

joemc99 wrote:

On topic, so I'll use this post!

Right, need to remove rad upstairs and move to different wall. This involves cutting back the pipes. Problem is, I am unable to locate the flush cock anywhere? There is one at the bottom of the hotpress (upstairs), but surely this is not it!

All indications point to a sealed system, pressure vessel, pressure valve, etc. Can I remove the rad as normal, shutoff water to the CH system, and relieve the pressure from the rad valve? Then I can cut the pipes back and not too much water will come out?

I have seen on some sites that a sealed system should only be touched by a pro as refilling is a problem! Any advice would be great!

If you dont have a drain valve, drain the system by finding the lowest placed rad in your house. close the rad valves (at both ends!). Remove the rad with some delecate and quick use of fingers to plug the holes at both ends of the rad (two man job).

Remove the rad and drain into a bucket / outside in the garden. Hook a hose upto one of the valves, run out to a drain (lower than the valve), open the value and the system will drain.

Reverse the process when you are done.
Jab