draining a system boiler

[GedDIY]

Need some of your expert advice please. Just moved into our new place. System boiler with a hot water cylinder. The radiators have been changed but i want to put some TRV's on them.

How do i drain down the system. Previous place had a combi and i just isolated the heating flow and return and used a drainoff. Do i do something similar here??

Advice and tips appreciated.

 

[namsag]

if by system you mean pressurised then , Yes close down auto air vents release pressure and do one valve at a time and there should be no need to do a full drain down...

 

[GedDIY]

its gravity fed ( i think). System boiler downstairs with a hot water cylinder. Pipes from this go into the loft to a couple of tanks

Was ok in last house with the combi. Just need some help with this. Do i have to drain down the whole system to change all the trv's???

 

[Dan Robinson]

You don't really need to - I changed 8 (or was it 9?) trvs the oother day and only took 12 litres from the system.

 

[namsag]

The term System boiler refers to a pressurized boiler what you have is a standard boiler. Better to just fully drain it down. There is a way to do it without draining using bungs but thats not really for diy

 

[Dan Robinson]

aaah go on... it'll be fun .

 

[namsag]

Not as much fun as snatching them and being the wrong thread..

 

[Dan Robinson]

Thats why the lord high plumber in the sky gave us ten fingers and ten toes..

 

[GedDIY]

Tell me how to use bungs. I feel pretty confident.

Dan. how were you able to change all those TRV valves without draining down

 

[Dan Robinson]

Twas a sealed system so everything naturally holds back under vacumn (although this was a four zone system which made things a little tricky)

I use a Dewalt battery powered hoover and work effing quickly.


With bungs you blocked the feed and vent pipe in the attic then you generate a vacumn in the system by draining off (remembering to tighten up the point at which you drained).

Close off the lockshield side of the rad (counting the turns needed). This can only be done one rad at a time and you always get a bit of seepage so this needs to be taken up. Never try and do more than one vavle at a time.

This is a simple enough process; and I have left a system under vacumn for over an hour (bought the wrong valve ) but you need a game plan and to know what you are doing otherwise things could go horribly wrong.

The more someone proclaims their competence/confidence, the more I worry. There is a thin line between confident and cocky