Old Central Heating problem

[John]

A friend has an old back boiler heating system (Baxi, I think) and an upstairs radiator is leaking - bottom of radiator has rusted through. Due to lack of funds and as the system is so inefficient that they don't use it, they wanted to drain it down or isolate the radiator. All of the radiators have only one regulator valve, the other side being a plain 90 degree union. There do not appear to be any drain points on the system unless on the boiler behind the gas fire. The system appears to be fed from the same header tank as the DHW system and there is no obvious way to isolate the cold water supply to the heating without also isolating the hot water tank - the only visible wheel valve being to isolate the hot water tank. The only idea I have is that it any isolating valves may be below the hot water tank which is in a cupboard above and at the end of the bath, the whole bathroom floor BTW is approx 6 inches higher than the rest of the upstairs floor which makes me think that it is to accommodate plumbing. Apologies for the length of this post. All suggestions gratefully received.

[meow2222]

It is very easy to add a drain point anywhere on half inch pipe, just connect a dracula tap. (Self cutting tap that clamps onto the side of an existing pipe.) The a valve can be fitted, or the rad replaced. Note that even if a crap performer, a sometimes half warm rad still gives out some heat.

However I wonder if your system may be gravity circulation, which would use much bigger pipes.

Fernox leak sealer might give you more time to arrange a real repair.

screwfix.com item 13768.

If one rad has rusted through, it wont be too long before the others follow suit. Your primax cylinder makes it impossible to use any additives to prevent corrosion. The whole system sounds lousy, money will be needed soon.

NT

[John Stumbles]

Sounds like a 'Primatic' system - you may find this on a label on the hot water cylinder. If you've definitely only got a large cold-water tank and no small feed-and-expansion tank then it is this type of system. If this is the case I think you'll have to drain down the system (from the drain-off c*ck on the connection at the bottom of the cylinder) and isolate the CH pipework from the cylinder (capping off the cylinder connections) before you can drain the CH whilst having the HW working again. DO NOT put any additives into the system before doing this - they will get into your hot water!

As meow2222 says you can use a self-piercing drain-off c*ck (or any other self-piercing fitting such as a self-piercing washing-machine connector) to drain off the radiator pipework at a low point.

[gasman pete]

sounds like you have a one pipe system..

[John]

Thanks everyone for the info, I'll pass it on. Indeed, the system does sound lousy.