How to drain CH without a drain valve (to replace TRVs)

[Higs]

I've done some searching on here and think I have worked out what I need to do.

The reason I need to drain the system is to change two TRVs that always seem to be either stuck closed or stuck open.

I've checked all the downstairs radiators and any visible pipework but I cannot find a drain valve.

One of the rads with a stuck (closed) TRV is by the back door.

What I plan to do is:
1) Wind down the TRV on that rad
2) Close off the return valve on same rad
3) Disconnect the return end of rad - catch water coming from rad
4) Fit a washing machine hose to the return pipe, sling the other end of the hose towards the drain outside and open the valve.
5) Have a brew
6) Remove return valve and replace with one with a drain valve (for next time)
7) Replace both dodgy TRVs
8) Reconnect everything and pressure up the system through the combi boiler

I will close both ends of every rad apart from the ones that need the TRVs changing.

Will this work?
What are the pitfalls?

Sorry if it appears that I'm over-thinking this but I don't want a house full of black, smelly water![/list]

 

[TCCHeating]

You're overthinking you have a sealed system.

Close any automatic air vents. Turn off lockshield valve and release any pressure into a container by loosening the nut between rad and trv. If you have closed any auto air vents then a vacuum should be created and water flow should stop. (Should be no need to close valves on the other rads).

When you are finished make sure you open the auto air vent up again before you fill and operate the boiler again.

 

[neiltheplumber]

Have you checked outside the building for a drain off? Sometimes we poke them outside. However what you plan to do is fine, you could put a nut and olive on the hose itself and connect it to the rad valve once you have drained the rad. Once connected, open valve and drain system! Easy but u dont need to close all rads.