system drain point

[mattmenzies]

I have a top floor (3rd) flat and am unable to find the point at which I should drain the central heating system.
I know it should be at the lowest point but can't find this is it likely that the valve will be hidden under floord etc.

Any hep appriciated

Cheers

 

[Paul Barker]

When I come a cross a system with no drain off (most of the time) I get an isolation valve ready with a stub of 15mm pipe in it and garden hose attached. Lead hose out to suitable drain, shut a rad valve and undo the pipe to it, bang the isolation valve on instead double quick. When drained fit a drain off.

You can look under the floor but unlikely to find anything.

 

[mattmenzies]

Cheers for that.

i'm i right in thinking that the proceedure would then be:

Close the valve to the rising main stopping the expansion tank filling,

then do your trick with the isolation valve. then the system will drain allowing me to carry out any work i need to.

Then connect evrything back together and turn back on the water???

How fast will the system drain, what I really mean is will the water have a lot of pressure behind it cause it would be really difficult to run a hose pipe down the stairs and guess down a sink or toilet is the only way??

Cheers

 

[Paul Barker]

If it's a feed and expansion tank open vent system it'll be fine down the loo, shower tray is better.

Manually open any zone valves/mid position valve, as system starts to drain open upstairs rad vents first then downstairs as you can, helps prevent airlocks on refilling, though some problems refilling are a certainty.

When refilling make sure zone valves manually open, leave as many bleed valves as you dare open a tiny little and try to jump around them fully bleeding one by one. Once some water has appeared in every rad you can close the valves and then go round one by one to finish the job. Bleed pump and any bleed valves associated with dhw cyl (if fitted).

Then start the system with boiler off but allow pump to run etc. keep switching pump between speed 3 and a position between speeds which in most pumps is off, but not all. wait during an off period until you hear air escaping up the open vent/cold feed arrangement. There should be a lot of gurgling and wooshing to start with, but the pump should get it shifted and stopping it and waiting allows the air to escape. Repeat multitudinoud times. Try different pump speeds, and occasionally cheack various bleed points including pump.

If a partticular leg won 't free of an air lock, shut down rad valves of all other legs to force motion down that leg.

If all else fails back fill from mains.

It's a right carry on in most homes, good luck to you.