Drain down combi system?

[dp]

Hi,

I have a combi boiler on a sealed system (worcester greenstar 25si), I want to remove/replace a radiator but it doesn't have an isolating valve on one side so I have to drain down the system.

Is this as easy as turning off the boilers electrical supply at the switch, connecting a hose to the drain c*ck and then opening up valves for it to drain?

And to refil use the water inlet at the boiler which tops up the pressure and then bleed rads as necessary and fill more etc.

Thanks

[chris French]

In message , dp writes

Yep, that's it. If you want to fully drain down then you will need to open at least some of the bleed valves on the rads. But no need just for doing one rad.

Don't forget to refill with inhibitor. Either use the one that comes in big syringe type affair, use ordinary package stuff and connect a flexible pipe to a rad top tapping and then put a funnel in the end of that and pour in via that, or if you have ladder type towel rad it may have tapping on top, just fill through one of those.

[Ed Sirett]

See the SealedCH FAQ

[dp]

Thanks for the replies!

I'd actually read the Sealed CH faq Ed but it didn't mentioned draining down, only refilling.

Another question I have is I have had the new combi fitted on an old system. A few of the radiator joints have been leaking a little and the pressure drops slightly each day. I know you won't be able to say for sure but do you think if I redo all the compression joints with PFTE tape (As it was a open system before there is none on the current joints) will that be enough or do you think all the pipework should be replaced?

[chris French]

In message , dp writes

There should be no need to replace the pipework. If it is compression joints that are leaking then just nipping them up a little tighter will probably do the trick.

[Ed Sirett]

I suppose I thought the draining down was so obvious that it required no explanation. Anyway it's boiler off and open the required drain point(s). The points will have any or all of the following 'features'.

a) They will be indoors. b) Even if outdoors they won't be over a gully. c) They will be the light pattern type which will leak profusely when you open them. d) Even if they are the heavier pattern with O-ring seals on the spindle they will come apart and leak. e) the washer will have welded itself onto its seat and the button on the jumper will pull out of the washer. This will make the flow only a trickle but if you try to extract the washer you may get a bit wet. f) alternatively the rubber washer will have turned to charcoal and break into two fragments. One of which remains stuck to the valve seat the other will partially block the outlet of the drain point. If you now reclose the valve it won't stop the flow of water. g) The point will not be the lowest point on the system. h) The point will only have been fixed to either flow or return pipes so preventing you from draining half the pipes below the level of the lowest rad. i) The outlet of the drain point will have been installed so close to the floor that it is impossible to get a tray underneath or to attach a hose without it kinking.

A smear of silicone grease or PTFE resin is the best way to improve leaking screwed and compression joints (IME).