Replacing a Lockshield Valve?

[BearTricks]

I thought, stupidly, that it would be worth taking a couple of radiators off the wall today to prepare for a week of decorating.

I should have known not to do anything plumbing related on a Sunday evening because last time I did a local emergency plumber ended up £150 better off.

It's not quite as bad today. I started draining the radiator, noticed that the lockshield was corroded a bit on the lower nut that connects it to the pipe and my fiddling with it must have knocked something loose because its now dripping very slowly.

All I need to know is how to fix the bloody thing. New valves look about £15 at Screwfix. Can I literally just drain the radiator/system, pop it off and screw the new one on? I've been on YouTube etc but I've found that plumbers are great at fixing leaks but generally terrible at making videos.

Any help would be appreciated. It seems too simple to hire someone to do it but I've learned that there's always something that's not quite as intuitive as you'd think.

 

[jimmy_s]

Pretty much take the old one off and replace. if you have to replace the tail screwed into the radiator then you will need PTFE tape or similar to seal the threads and you might need a radiator spanner to tighten end into the radiator.
Easy enough to do.

 

[sunnybob]

Just make sure once its leak proof to bleed ALL the radiators, its normal for air to migrate from one rad to the next.Start with the lowest rad and work your way upwards.
And check the system pressure on the boiler gauge before you drain and refill to the same pressure.

 

[Rorschach]

£15 you having gold plated ones? :lol:

Should only be a few quid each.

Pretty straightforward job once you have drained the system down. Good opportunity to flush out any sludge too.

 

[Sheffield Tony]

Simple job unless ... it becomes more complicated. The corrosion is on the compression nut on the pipe ? So probably it is the compression fitting seeping, so using the old nut and olive, it may still leak. To fit a new nut and olive means getting the old one off, but if it has been overtightened the end of the pipe may be crushed in a bit, so then you have a soldering job to cut the end off and extend it with a fresh bit. And if the system has not been drained for a while, expect silted up drain cocks, and possibly leaky isolator valves after you have turned the water off and on again.

If this sounds like bitter experience, it is - I replaced my hot water cylinder in Feb, and it took 2 days with all the unexpected side effects !

 

[HappyHacker]

Simple job unless ... it becomes more complicated. The corrosion is on the compression nut on the pipe ? So probably it is the compression fitting seeping, so using the old nut and olive, it may still leak. To fit a new nut and olive means getting the old one off, but if it has been overtightened the end of the pipe may be crushed in a bit, so then you have a soldering job to cut the end off and extend it with a fresh bit. And if the system has not been drained for a while, expect silted up drain cocks, and possibly leaky isolator valves after you have turned the water off and on again.

If this sounds like bitter experience, it is - I replaced my hot water cylinder in Feb, and it took 2 days with all the unexpected side effects !

Tony is spot on: but a dodge to save starting the refitting of your central heating system is to neatly put some PTFE tape over the olive so that it gets compressed on both sides of the olive when refitted.

I once started a simple job on a hot water cylinder, to fix a small leak, and ended up replacing the cylinder and most of the pipework around it.

From experience don't use the blue PTFE fluid sold by one of the main DIY/trade shops, it sets solid and will never come undone.

 

[sunnybob]

There are even two thicknesses of PTFE tape, the thicker one is for gas.
Any minor corrosion on the pipe or fitting can be removed with wire wool, but plug the open end of the pipe before you use wire wool, or the fluff will fall into the system and make a nice ferric sludge.