Changing TRVs - 2 queries

[John Forbes]

I changed 6 TRVs this weekend. Re the bit that screws into the body of the rad, two of them on the old valves had flats that I could get my wrench onto to get then out, but for the other four I had to insert a large hex radiator key into the body of the fitting and pound hard with a mallet to loosen them. As I was doing this I kept imagining the severe damage I was causing to the body of the rad ...

Touch wood everything seems okay, but was I doing the right thing - should I have had to resort to brute force, or should I have done something else a bit more clever? The old valves seemed to have white putty stuff around the threads.

ANOTHER "did I do the right thing" query from the same job - the copper thingy inside the compression washers attaching the old valves to the vertical 15mm inlet pipes were "stuck" (compressed, I supposed) onto the tops of these pipes. So I cut 3" off each pipe and then connected an in-line shut-off valve and a short length of new 15m copper up to the correct height. Again, should I have done this differently?

I know that asking for advice after the job's over seems silly, but I've still got another 4 valves to do next weekend.

Thanks

John Forbes

[Christian McArdle]

Personally, I just used the old olive and nut on the new valves. I can't see a problem, provided they don't leak in practice and use the same threads. If the olive is damaged, then there are methods for removing them, although even then the pipe may be sufficiently damaged to not allow a new olive to be used, in which case the pipework needs replacing. I'm not sure I'd want isolation valves on show on the radiator tails, though.

Christian.

[Set Square]

Presumably the turned up bit of the allen key was shorter than the spanner which you used on the valves with flats - so you couldn't apply as much torque by hand? Under these circumstances, I would slide a foot of steel pipe over the allen key to get a bit more leverage, rather than hitting it with a hammer.

The white putty will be Boss White. You could have used some more on the new valves, or cleaned up the threads in the rad and used PTFE tape. I hope you one or other - and that the new valves don't leak.

As Christian said, you could probably have left the nut and olive on the pipe, and screwed it onto the new valve. Was the isolation valve a quarter-turn ball jobby, with a screwdriver slot? These are not full bore and do cause a certain amount of flow restriction. This doesn't matter on small to moderate radiators but wouldn't be a good idea on big ones. If you're going to do that, it makes sense to have a drain valve between the isolator and the rad valve. This makes it much easier to drain the radiator in future.

[Big Phil]

Sounds similar to what I did when replacing mine. Didn't have to resort to a hammer, but it was a mighty tug. The white putty stuff was presumabley PTFE tape, which would be advisable to replace when inserting the new inserts.

I presume you mean the olive? I got these off by either using grips to 'wiggle' it free, or by cutting it off very carfeully with a junior hacksaw, then cleaning the pipe up to reuse it.

The big hassle is draining the system and refilling it everytime, unless you're not using it yet. I turned my heating back on last week, but I'm in the freezing north!

[Dave Liquorice]

If you plug the feed and expansion pipes then no air can get in so no water can get out of a *single* hole, in theory. You can get bungs for the feed and expansion pipes, I have a set but have yet to use them for the designed purpose.

So bung up the feed and expansion pipes, close both valves on the radiator you intend to work on, open the bleed valve and loosen the joint between valve and tail of the valve you intend to change and catch the radiator full of yukky water (don't get it on the walls or carpet!). Once drained, change the tail etc and swap the valve heads, I suspect some water will come out of the open pipe but not a great deal (in theory), another bung might be useful whilst you fit a new olive and swap nuts if you are doing that.

[John Forbes]

Thanks for all the advice, everyone.

- Christian; I didn't know you could re-use olives - I assumed they would be mechanically distorted and had to be thrown away

- Set Square; putting a bar/tube onto the end of the rad key to get extra leverage seems an excellent idea. Yes, I used PTFE tape. You've now got me worried re restricting the flow with the shut-off valves .... have to see how the heating works when we get some cold weather

- John Laird; yes, the valves screw into a central bit between the two halves of my double radiators. Thanks for tip re silicone sealant on olives

- Big Phil; absoluteley agree re draining down the system being the biggest pain, especially as I can't figure out how to do this without turning off all the water in the house!

- Dave L; .... am I brave enough to try your method .... don't know!

Thanks again

John

[Neil Jones]

If you have a header tank, can you tie the float valve up so that even when empty it's won'r refill?

[Dave Liquorice]

I'm not sure I am without lifting the carpet in the immediate vicinty. B-) And I have (new) gate valves on both the flow and return of both CH loops so it should shut down very tight.

[John Laird]

Not any old silicone, I should have pointed out. I have a small tube of Fernox LS for this. Be aware that some people will frown on its use ;-)

As the valve tails screw into a strongly-mounted fitting, you should be okay using whatever leverage is necessary to remove them.

[Phil Addison]

Normal in-line shut-off valves (service valves officially) have a very restricted bore and are meant for use where there is a fairly high pressure feed, e.g in feeds to taps. They are not suitable for your central heating circulation which has a low pressure pump, and they can restrict the flow to the radiators. You might get away with it, but at the very least they will upset the balancing - if it was ever balanced in the first place. Apart from that, they are quite unnecessary as there are other ways to prevent water leakage when removing radiators as mentioned further up.

Full-bore valves are available if you really want to fit them (or is that what you used anyway?).

Phil The uk.d-i-y FAQ is at

NOSPAM from address to email me