Can plumbers change TRVs without draining the system?

DIYNotIan · 20 Jul 2013

Hi all

I have a plumber coming soon to drain the system, balance rads, change a broken TRV, and add some inhibitor to the system.

We did toy with the idea of changing all our TRVs (as they are quite old). Our reasoning was that "he might as well, seeing as the system is drained". But we based that on the presumption that the system MUST be drained to change a TRV.

If it doesn't, then we might as well only have the broken one changed, and then change any others in the future should they break (and NOT have to pay to drain the system again).

But can that be done?

Cheers guys

Max

newbuildinstaller · 20 Jul 2013

i do but im very fast and brave!! I do mains stop cocks too!!!

If you have tanks in the loft and your plumber is any good he will bung the vent and feed (making a vacuum) and do it live.

If a combi/unvented he will knock the pressure off and again do it live.

If he is a girl he will drain it

DIYNotIan · 20 Jul 2013

We've got tanks in the loft.....

Good to hear it can be done. The plumber coming IS draining the system as he is adding the inhibitor etc. I was asking for future reference should a TRV go later down the line. At least then I can call about until I find a similarly brave plumber!

petit_pablo · 21 Jul 2013

Wouldnt need to drain the full system to inhibit either. Either put inhibitor into radiator after doing the valve or drain off just enough water to empty the tank and airing cupboard pipework

bazdaman · 21 Jul 2013

Easier to bung or release pressure than draining, and systems can fill badly so i always avoid draining where possible.

doitall · 21 Jul 2013

Make sure he cleans the header tank before he drains down, you don't want all the crap in the system, or you'll have bigger problems.

JohnD · 21 Jul 2013

if you have a feed and expansion tank in the loft and are moderately handy, you could bale out the mud from the tank yourself and circulate a cleaning chemical prior to his arrival so that the loosened dirt comes out when he drains it. A plain drain does not get much dirt out. If you find a lot of sediment in the F&E it is a clue that a clean would be a good idea. Make sure it has a close-fitting plastic lid as well to keep dust and wildlife out.

reply if you want to do it, it is not difficult if you have a spanner.

BTW a single TRV change can be done without draining, but if you are doing several, IMO it is less trouble to drain and do them all in one go.

Dan Robinson · 21 Jul 2013

Well experience has shown me that the more you change with a bunged system, the easier it gets working top down.

DIYNotIan · 20 Dec 2014

JohnD said:
if you have a feed and expansion tank in the loft and are moderately handy, you could bale out the mud from the tank yourself and circulate a cleaning chemical prior to his arrival so that the loosened dirt comes out when he drains it. A plain drain does not get much dirt out. If you find a lot of sediment in the F&E it is a clue that a clean would be a good idea. Make sure it has a close-fitting plastic lid as well to keep dust and wildlife out.

reply if you want to do it, it is not difficult if you have a spanner.

BTW a single TRV change can be done without draining, but if you are doing several, IMO it is less trouble to drain and do them all in one go.

Hi JohnD

The months passed, the seasons changed, and I've finally got around to trying to get this sorted. I started a new thread here:

//www.diynot.com/diy/threads/which-of-these-three-loft-tanks-is-for-the-central-heating.421342/

The last post expresses how I'm a bit confused as to what I need to do! If your offer still stands to talk me through it I would appreciate it immensely!

Many thanks

Max

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Can plumbers change TRVs without draining the system?

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