Bleeding or purging is carried out to avoid the possibility of an explosive air/gas mixture existing or forming in your gas appliances.
In the event of a gas-related emergency such as a leakage, bleeding your gas appliances is important as any trapped gas in your appliances could have the potential to ignite and cause a fire. Follow the steps set out below carefully and safely to bleed gas through your appliances. If you’re unable to do this or not confident about bleeding your appliances, please call your gas distributor for help. You can find their details by entering your postcode here.
- Turn on one burner until gas is detected.
- Let the gas flow for a few seconds, then turn off and allow time for accumulated gas to disperse.
- Turn on one gas control valve again and apply a continuous burning flame at the burner until the gas is alight and the flame is stable.
- Continue to purge each burner through its respective valve.
Hot water system
- Switch off the heating system and let it cool for about an hour before moving to the next step
- Locate the bleed valve on the main system tank. This is usually near the bottom. It may look like a standard hose outlet with threading on the edge.
- Cover the bleed opening with a piece of old cloth. This will be used to catch any excess water coming out of the bleed valve. The water will be hot, so make sure to protect your hands with a pair of gloves and cover your eyes with glasses. If your boiler is located in a spot that has flooring you would like to protect, place a bowl or newspapers beneath the valve to soak up any water you miss with the rags.
- Open the bleed valve slowly. You should hear a hissing sound as air is pushed out of the system. Take caution as this air could be very hot.
- When water starts to come out the valve, turn the handle to close it.
- On some systems, you will need to add more water after a bleeding procedure. In general, most boilers need slightly more than one bar of pressure when they are not operating, but some may require more. The usual procedure to re-pressurise the system is to open the valve on the water supply line until you see the gauge on the boiler go over the required minimum pressure.
- Restart the system. Check around the boiler for leaks.
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