combi boiler / trv's

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Hi, we are changing an old rad valve for a new trv. We have a combi boiler. Do we need to drain the entire system to change the rad valve or can we just let the pressure out of the boiler from the prv?

Many thanks
 
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drain the pressure off the system and turn both rad valves off on the radiator you are changing the rad valve. Drain the rad down remove the old tail from the radiator and replace with the new one. Then put an old towel round the pipe of the old rad valve and swap them over. Make sure you use PTFE on the new tail. nip up and fill up.

Hope that makes sense
 
so i just need to release the pressure through the prv? and not drain the system from the drain off point?

Thanks
 
DON'T use the prv to drain off. Quickest way to cause it to malfunction. Dirt from system gets on to the seating.
 
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can we just let the pressure out of the boiler from the prv?

sure you can then post on here as to why it leaks afterwards :eek:

drain the pressure off the system and turn both rad valves off on the radiator you are changing the rad valve.

close the aav on the boiler as well :idea:
 
can we just let the pressure out of the boiler from the prv?

sure you can then post on here as to why it leaks afterwards :eek:

drain the pressure off the system and turn both rad valves off on the radiator you are changing the rad valve.

close the aav on the boiler as well :idea:

why close the aav? you are undoing one joint to quickley swap a compression joint. Hence the old towel as a minute amount of water will be released.
 
why close the aav? you are undoing one joint to quickley swap a compression joint.

the aav will let air in if the pressure is off

as for quickly swapping a valve if you hit a snag you dont get a flood :idea:
 

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