Heating system drain down

Hi
Often with bungalow pipe work, it's a circuit in the roof, with pipe "drops" to radiators,

Have a look round, do you have pipes dropping to each radiator, or just one and all the circuit is below the floor?

Try to work out, can just isolate and drain the section you are working on

Regards
Peter

 

Hi Steve.

1) I would switch the whole darned thing offski - ie there should be a single switch on an FSU or perhaps a plug that isolates everything to do with the system. You don't want a pump to start running for any weird reason whilst dry.

2) You drain from the bottom. Ideally there should be a draincock on either a rad valve or the pipework. Is there? If not, then now's the time to fit one. If it isn't too much trouble, you could even 'tee' in to the lowest flow and return pipes and take a couple of 15mm pipes through your outside wall (almost certainly below DPC level) and terminate them in draincocks outside - that'll make any subsequent drain-downs very easy . Failing that, add a draincock with serrated hose nozzle on to a pipe feeding a downstairs rad - one near an outside door eg: http://www.screwfix.com/p/chrome-angled-radiator-valve-drain-off/70408

3) Ok, do you want to drain your rads? All of them? Or chust some? If there are any you don't really want to drain, then simple close both valves on that rad fully. (NB - there will be an adjustable valve (perhaps a TRV) and a 'fixed' one called a 'lockshield'. It is important that you count how many turns the lockshield takes (clockwise) to shut off, including part-turns. Note each one down on a piece of paper and stick it to the rad or summat. You can then open each rad to the same amount and hopefully find your CH system is still 'balanced'.)

If you do want to drain every rad, then leave the lockshields as they are and open the TRV side fully.

Shut off the supply to the F&E tank so it doesn't keep filling, attach a hose to the lowest radiator or drain cock and open the cock. Your system should drain out until your F&E tank is empty. To drain the rads you want to drain, start upstairs and open each bleed screw - you should hear it whistle as it draws in air... Just open them all. If the ones on the downstairs have water come out, then wait a while for the top ones to drain first.

4) Refill - make sure all bleed screws are closed and I think I would shut the TRV rad valves too to begin with. Pour your inhibitor in to the empty tank and open the supply to it. let it fill until full. The pipe system should have pretty much filled by now, and you'll only get air locks in poorly-designed layouts (eg with pipe runs which go up and down in wobbles!)

Now start at the bottom floor and furthest away rad - open the bleed screw and air should start to come out if the lockshield was left opened (ie you allowed the rad to empty before). Let the rad fill like that for a couple of minutes so's it's getting refilled from the 'return' side - listen for glugs and gurgles - and then you can open the TRV side to allow it to also fill from this end - you might possibly hear the ejected air speed increase (or you might not - doesn't matter...). Shut off the bleed screw when water comes out. Move on to the next nearest rad on the ground floor.

Then repeat on the upstairs - furthest away first.

5) When all done, turn the system power back on and the CH to 'call for heat'. Expect lots of glugs and gurgles, but that's normal. Depending on your boiler type, it may have an auto air event inside to expel any trapped air, but most air will (should) simply escape up the 'vent' pipe which ends over the F&E tank. Do you have any other air vents on your system? It is quite common to have a short length of vertical pipe with an auto vent on top or even a simple drain cock - this catches air as it flies past the pipe below and it can then be simple vented off (but turn off the pump first or you risk drawing air in!).

6) You should have air locks, but if you do come back on here! What will almost certainly happen is, any air bubbles being pushed around will end up either being vented orf (through the vent pipe) or else end up inside a rad. Ok - important - turn off the boiler and pump before opening bleed screws from now on.

If you find there is an air-lock - eg there's one or more rads which ain't heating up even tho' the valves are definitely open - then shut off (TRV side only) as many other rads as you need to so's you force the pumped water more powerfully in to that cold rad. Shut orf the boiler and bleed.

 

In theory any drain cock will drain the system - provided it's at its lowest level.

The rads with draincocks - is one on the TRV side and one on the lockshield? Chust wondering - it doesn't have to be.

Bear in mind that, after draining using these 'cocks, there will still be water sitting in the pipework below floor level, so be ready to catch this (or simply let it drain on to the soil/ground under your floor.)

You might want to take the opportunity to add a further draincock from the lowest pipe under the floor, and take this out through the wall, terminating in a draincock outside. But, if you find the new rad/pipe changing process isn't a problem, then you might not want to bother...!

If your system is in good order - nice clean water - then by all means shut off all the rads you don't need to drain, and that'll save time and also probably make refilling more easy - you'll then mainly only be draining the supplying pipework, so a lot less volume.

If the water is brownish at all, then I'd personally want to drain it all right down and refresh.

As to which 'cock to drain from, I don't think it matters much. Drain from one, and when the water stops flowing open the other one too - and see if anything comes out .

 

Hardness hopefully shouldn't be an issue for a CH system, as it's the same water that's circulated over and over again - so no extra 'salts' are being introduced.

I was mainly wondering about corrosion - especially internal in the rads. This will show itself by the water being brownish and - if you actually remove a rad - having very black water trickling out when you tip it on its side.

 

Hi,
There might be draincocks fitted below the floorboards. My father's house has two such fitted, the drain hose appears through air bricks, cut off level with the outer bricks.
I've used, with great success, pipe freeze, providing compression fittings (not solder) are used to extend/replace/alter pipework. Screwfix part 20183. Follow the instructions carefully! Saves time and inconvenience on draining down the system.