Central Heating Drain Valve

chloesdad

Has anyone had experience with installing a self-tapping drain valve for their central heating system? 

My system does have one at the moment but it’s in an area that’s quite hard to access so ideally would like to put a new one in, but without having to drain the whole system down if possible!

tacpot12

I've not put one of these, and I would be concerned about introducing a restriction into the flow of the central heating system. It will provide a point around which crud in the system will collect and further block the flow. 
 
When you need to drain the system, you could fit one then, and then cut out the damaged pipe and fit a tee with a proper drain valve. 

Jeepers_Creepers

I agree with Tacpot - I would consider these only as a temporary measure. 

Can I suggest that you wait until you actually want to drain down your system, then buy one of these and a yorkie type (or even push-fit if it'll look ok where you do the job) of slip-tee & draincock. Fit the self-tapper in order to easily drain the system and then - whilst drained down - replace it with the 'proper' one. As Tac says, you'll either have a 'hanging chad' in your pipework which could restrict flow, or - worse - an actual loose chad flying around...

This video speaks volumes by showing how to replace the self-taper type afterwards... (warning - turn the volume down. I mean, right down. To zero. Or lower if you can.) https://www.youtube.com/watch?v=ycT_osd9Tyg

Alanp

Don’t do it, many years ago I tried the very same thing using one of those self tapping thingys, I couldn’t get it to seal properly despite draining and refilling several times I eventually resorted to bodging it with a fitting I had as I could not be ar#ed going to B&Q to get a proper fitting, I had a new boiler fitted and the plumber had to alter all the pipe work anyway and he put a proper drain in then

EssexExile

The "hanging chads" that JC talks about above are a real problem. The piece of pipe that is cut out during fitting just folds back out of the way, partially blocking the flow. Over time it usually folds back again into the way completely blocking the hole you cut.

DiddyDavies

Depending on how your CH system is installed, you may well not have to drain down the whole system.
In my house, some of the radiator feed pipes in the attic have stop !!!!!! valves in the lines (both the feed and return lines) so in my case, it would only be necessary to drain down a small part of the system.

chloesdad

Thanks all for the comments. Looks like a unanimous no to the self-tapper! 

Jeepers_Creepers

Not as a permanent solution, but fine if it helps you to drain down your system - and then replace it with proper stuff as part of the whole job. You know that Chloe will not be happy if you mess things up :-)

nofoollikeold

Personally I'd say no at any time.  If the copper disc it cuts out comes loose it could wash up anywhere in the system and cause a blockage, or a mind numbingly irritating noise.