28mm drain cock?

[flutterbye]

There is a stuck draincock on the return pipe close to the boiler. The pipe is 28mm.

When I get around to draining down the system in the summer (to fix up a load of things) I want to replace this drain cock but I can't see where to buy a replacement from.

Do I need to buy a 28mmx28mmx15mm tee and then hook up a 15mm drain cock into the reduced tee?

Oh and while I'm here, would anyone mind telling me what I need to search for to replace the stop-end that is currently at the end of a vertical 22mm pipe in the airing cupbaord? I think I need some kind of bleed vent so I can remove trapped air from there but I'm not exactly sure what to buy.

Any advice v gratefully received with thanks!

 

[JohnD]

I am a householder not a pro, but I had something similar. It is an advantage to have a full-bore drain cock, as it is very fast, and the good flow also helps wash out sediment. An ordinary 15mm drain cock has very poor flow. However the heat of a primary circuit tends to make cock washers perish and seize. One way is to have a fullbore gate valve feeding a stub pipe. If the gate is normally closed, the stub will not get very hot, only by conduction a matter of inches. Gate valves do not give a perfect seal, so on the end of the stub you can put e.g. a hose connector, with a capnut to blank it off and prevent drips when not being used, or a ballofix or similar water-tight valve. If you just rely on the gate you will get drips. You could even tee off a stub with no gate, and rely on the length of the stub to prevent it getting very hot.

I used a 3/4" washing-machine valve on the end of the stub, because you can get a hose connector that allows you to drain with a good seal and no drips

 

[TicklyT]

Probably easiest to fit a 15mm drain cock in a reducer, or a 28 X 15 X 28 Tee. Avoid the light pattern type B drain cocks - when opened, most of the water leaks out around the spindle threads. Type A drain cocks have a gland on the spindle, so less chance of the water running up your sleeve.

Same for the bleed valve, use a 22 X 15mm reducer, and a 15mm air vent cap.

http://www.screwfix.com/prods/33206/Plumbing/End-Feed-Fittings/Air-Vent-Cap-15mm-Pack-of-10
Only problem with that one is what to do with the other nine.

 

[flutterbye]

Thanks to both for your suggestions.

JohnD: I followed most of what you said and it made sense except perhaps that the hosepipe is much narrower than the 28mm pipe so may as well tee into (say) a 22mm ?

Also, I didn't understand how you would fit the 3/4 inch washing machine valve on the end of the 28mm stub? I guess there's no chance of a link to the kind of thing you mean? Thanks again though.

 

[JohnD]

You are right, they all seem to be 15mm x 3/4" BSP now. I had the idea you could get them for bigger pipe.

http://www.screwfix.com/prods/25555/Plumbing/Pegler-Brassware/Pegler-Washing-Machine-Valve-15mm-x