Draining central heating - vaillant combi boiler

[tattrat]

I have just removed a radiator in the time honoured fashion. However, one of the valves seems to leak from where it joins the pipe. Indeed it would appear that it may have been doing this before. I would therefore like to drain the system so that I can properly cap off this pipe.

The system is a combi system (relatively new) running off a vaillant boiler. It is a system whee everything is in the boiler (i.e. timer and thermostat).

The only cock that I am aware of is the mains water one. Is there another lurking somewhere else? Which do I need to shut off in order to drain the system? I am happy to drain the system and leave it drained for a couple of weeks, when my plumber is coming along to remove and move a number of radiators and rationalise the plumbing. I the mean time, I will, at the very least, need to cold water function, and hot would be handy too. But I have no need of heating for the time being.

Can anyone help?

Thanks in advance.

BRendan

 

[chrishutt]

The Vaillant boiler has isolating valves on the heating flow and return connections underneath. If you can identify these and shut them, and switch off the heating function, you can drain the heating circuits but still use the combi boiler for hot water.

 

[tattrat]

The Vaillant boiler has isolating valves on the heating flow and return connections underneath. If you can identify these and shut them, and switch off the heating function, you can drain the heating circuits but still use the combi boiler for hot water.

Thanks for that! Now for the further questions....

Looking at the boiler there is a little key to open close "COLD WATER MAINS" or "C.H.RETURN".

SO do I close both and then drain system? Do I then need to open mains water to later have just the hot water function?

Thanks in advance.

Brendan

 

[Gasguru]

The cold water valve has nothing to do with the heating circuit.

The flow and return valves are on the extreme left and right pipes. The newer Vaillants are operated with a screwdriver unless they have been butchered (common) in which case 4mm hex key will fit (and does the job better).

 

[tattrat]

Thanks for - Job done!

Brendan

 

[austin1]

I have recently done a similar job to this and thought I would give you my experience of a problem you may encounter when you refill your system. You may find that the radiators do not fully heat and that the boiler pressure remains low. If this happens the solution is to simply look for the flexible pipe on your boiler (if i remember correctly it connects across your heating pipes) that will have a service valve on it. Open this valve to refill the system whilst also monitoring your boiler pressure until it reaches about 1.5bar. This may not actually happen to your system, but it did to mine and it took a lot of phone calls, time and messing about to carryout a very simple thing.

Hope this helps.

 

[tattrat]

Thanks for the tip. Fortunately the plumber will be refilling the system - phew!