Change TRV - How to drain system?

[trikster]

I have a Worcester Bosch Greenstar 42CDi combi boiler and I need to replace a TRV on a radiator.

I understand that to do this I need to drain the system, however I don't have any drain valves on any of the radiators and my boiler is pretty much boxed in by kitchen cabinets.

Any ideas how I can drain the system? (and do I need better access to my boiler to do it?)

Regards

Richard

 

[opps]

Have looked outside for a drain down point? Sometimes plumbers poke them out of air bricks.

 

[ollski]

Easiest way is just to put a tray under the rad valve and crack the nut so it drains from there. You'll need to snatch the valve to a point as the auto air vent in the boiler will probably still bo openso it will slow right down but not stop....have some towels handy

 

[trikster]

Have looked outside for a drain down point? Sometimes plumbers poke them out of air bricks.

Thanks for the reply.

Yes, unfortunately nothing out there apart from the condensate output pipe from the boiler.

 

[trikster]

Easiest way is just to put a tray under the rad valve and crack the nut so it drains from there. You'll need to snatch the valve to a point as the auto air vent in the boiler will probably still bo openso it will slow right down but not stop....have some towels handy

Hi ollski, thanks for the reply.

I did consider this and can still follow your suggestion. I think I will then have a different issue of refilling the system if inhibitor needs to be added but this is a different topic

Richard

 

[trikster]

Easiest way is just to put a tray under the rad valve and crack the nut so it drains from there. You'll need to snatch the valve to a point as the auto air vent in the boiler will probably still bo openso it will slow right down but not stop....have some towels handy

I presume this also the same solution if I need to swap a lockshield valve on the other end?

 

[ollski]

Yes same thing, presume the rad tails don't need changing?

 

[opps]

Another alternative is to use (new) bin bags to drain down an existing ground floor rad (after closing both rad valves). Once you have taken it off you can Frankenstein some half inch fittings and a length of hose pipe. Connect it to the rad valve, run the hose pipe out of the front door, open the valve, and drain down the system. Once everything has been drained down you can then replace the valve with one that has a drain off point built in.

https://www.screwfix.com/p/chrome-angled-radiator-valve-drain-off-15mm-x/70408

 

[trikster]

Yes same thing, presume the rad tails don't need changing?

I have fitted a new Rad which came with new tails but wasn't brave enough to tackle replacing the TRV and Lockshield at the same time

 

[flameport]

I understand that to do this I need to drain the system,

Not necessarily.
If the other valve on the radiator is closed, it's really only the water in the radiator and a small amount from the pipe that is drained, most of the rest will stay in there.
Just make sure only one valve / pipe / other is open at a time - any auto air vents will need to be closed.

 

[Elkato531]

This kind of job is very straightforward if you know what your doing and would take a pro about 15mins. You may have to pay for a whole hour but it would be done quickly and cleanly without the need for draining the system or removing radiators. Cleaning the carpet will cost you more if you get it wrong.