I want to fit a valve to a radiator which is on top floor. The system is pressurised to 2 bar with an expansion tank above the boiler in the garage. The tank is red and is the type that will have a diaphram inside to hold air. If i let out all the air and shut off the controls at each side of the radiator, can i fit the valve without having to drain the whole system? I realise the contents of the radiator will escape but its the in pipe im concerned about. Secondly what is the ideal way to get an inhibiter into such a system?

John, September 2008

Well, i didnt drain the system and i did the job today myself with no problems. Perhaps plumbers would drain the system to make the job last! The last plumber i had here charged 35 an hour and forgot parts so was going to drive about 20 miles return to fetch them all on my time. I went instead. He had even got lost coming to my house. Makes you wonder.

John, September 2008

Thanks Gary. Pity i have to drain buts thats life.
There are 9 radiators upstairs. How will i know how much to drain out at the boiler? To refill the system i will have to turn on a tap until the pressure reaches the current level and bleed the radiators as you say. How can i put rust inhibiter into such a system?
The downstairs has underfloor heating so i assume that is separate from the water in the radiators. The plumber who fitted 4 such valves upstairs in 2006 drained the system and the underfloor system did not appear to be affected.

Vincent, September 2008

hi letting the air out of the expansion vessel wont help you so no need to empty the vessells air !!!!
no matter what u will ave to drain the water from the system if its at the top of the system then ull only need to part drain the systen just enought to empty the radiator and pipe work to the radiator. re-pressure the system and bleed the said radiator

gary, September 2008

I thought the purpose of this site is to find out how to do things!!

John, September 2008

thats not how to do it.
leave the pressurised tank alone.
if i was you i'd get someone who knows what they are doing.

hi-spec plumbing & heating (essex), September 2008