how to flush out vented central heating system?

[caesarmanager]

I'm planning on flushing it though with mains adapted by a hose. Theres no airing cupboard as the hot water is fed off an gas wall heated not a cylinder. The cold feed to the system exits the bottom of the tank then runs down a wall cavity I think so can't realy get to it to cap it

 

[yerino]

Ah, I see!

Well when needs must maybe a bung is your only option, I however have never trusted one enough to use it and I'd prob jus alter the pipework in the attic to incorporate a form of isolation (somehow!!).

I'll leave it in your more than capable hands

 

[dextrous]

The point about the bungs is that you aren't actually pressurising the system much while you're flushing it through. Even if it did give way, which I doubt will happen, the FE overflow pipe will give you a warning.

 

[caesarmanager]

Thanks how much are the bungs do u no? Could I alternativly just flush out through the FE system. Just letting the system fill through this then drain off repeating this a few times?

 

[dextrous]

Think that pack of bungs was about £17 from screwfix, but yo will probably be able to get a single one cheaper elsewhere (a plumber merchant will be able to determine the right size for you).

As for flushing via the FE on constant flow - now't wrong with it but the pressure and flow rate will be much less than the one you originally intended. Bit like the difference between a hose and a karcher when you're washing the car.

 

[caesarmanager]

Thanks dextrous so to flush through the FE cistern do I let the system fill up til the cistern stops filling ( with the rads shut) then open drain off and repeat til water at drain off becomes clearer? Thanks for your help so far

 

[dextrous]

Don't suppose your plumbing skills extend to relocating the FE tank a bit? 'Cos if you did, you could incorporate that gate valve on the outlet as suggested, and a isolator valve feed teed into this supply pipe afterwards. Would make it easier if you ever want to flush it out in future and if you have a helper to control the isolator, will fill up the system a bit quicker too

 

[dextrous]

Thanks dextrous so to flush through the FE cistern do I let the system fill up til the cistern stops filling ( with the rads shut) then open drain off and repeat til water at drain off becomes clearer?

Just connect the hose to the drainoff point and start draining water. Then go and have a cup of tea or three - no need to start/stop like you suggest. You may want to get some sludge cleaning chemical and run the system with it in for a week or so before you do all this, just to loosen what you can.

PS with a name like yours, don't do any of this tomorrow. Beware the Ides of March, Caesar

 

[caesarmanager]

Thanks will it still get round most of the system with the drain off open all the time? Again thanks alot for your help

 

[dextrous]

Thanks will it still get round most of the system with the drain off open all the time?

Oops, there is that of course. Depends which pipe the drainoff is on.