Fitting a drain to a rad.

Why not either solder a boss into the rad and screw a tap into into it, or just solder a tap direct into the rad? By tap I mean c*ck, brass, small, such as available for C/H rads.

Rob Graham

When I take a radiator for repair they usually block the drain off. They then no to work after a while. brass taps seize. plastic taps break.

Having said all that, you could go to a wrecker and get the tap and fitting from an old radiator and sweat that into you own radiator. There is a fitting that is hex bar and brass plug type tap into that. The benefit of that is you can get a spanner onto the body and not twist the fitting out of the radiator when undoing the plug if its tight.

It would not actually be much help: when changing the coolant it really needs a good flow to take out all the crud from the bottom of the rad, a drain tap will not give a fast enough rush of coolant. With modern anti freeze it is only a once a decade job after all.

It would on a classic Mini, ever tried to get the bottom hose off the rad on one of them? ;-)

I was thinking more of a boss and screw in plug. Same really as the filler on the top.

No 'crud' in this all ally engine. And I wasn't thinking of a drain tap - more a plug rather like the filler on top.

As regards the anti-freeze, I'm wary about using long life stuff as it's said it isn't intended for copper rads and heaters, and can damage them. So change normal stuff every couple of years.

why not solder in a 15 or 22mm elbow or a tank connectorand put a lever arm ball valve on, then you could get the tap to a really accessible place and even drain without tools.

I've often pondered about using these, link:

Brass bodied ball valve, various fittings available, you may be able to braze one on.

regards

David

But I'd still need a spanner to open the filler after draining...

I'm not keen on any form of tap as it will be mounted on the rear of the rad not underneath. So quite vulnerable. The brass is quite thin and anything sticking out strikes me as a risk.

so try get a brass bush with a blanking insert from a plumbers merchant.

Would the radiator drain if you turned it upside-down? Someone's made a jig that'll do that in-situ:

Before I posted here I looked at the Screwfix site. Couldn't fine exactly what I'd pictured in my mind. Which was a brass T shaped boss with a female thread and a T shaped plug with washer which screwed into it.

Sounds like a lot of work for something that only needs doing every few years. However if I had to I'd probably make a valve. A little offcut of round brass about 3/4" o/d and 1/2" thick nicely squared off in the lathe, drill and tap that for an 8mm bolt and fit that with a rubber washer or just a metal washer and some silicone sealant. A 1/2" rubber tap washer with the right size hole in it should do nicely. A bolt with a built in underhead washer would be nicest.

If you silver soldered or brazed that over an 8mm hole in the rad it would be nice and sturdy with nothing flimsy sticking out to break off.

Here's your flanged setscrew so you get a nice seal with no separate metal washer to add a leakage path.

that is what I was thinking of too. if you look in toolstation catalogue (often better than screwfix) they have the plug and suitable bushes in various sizes, only pennies each, but their free delivery is on 10 pounds and above. they have a trade counter not too far from you in Croydon.

44643 is a three quarter plug 8667 is a brass flanged back nut or 42593 is a hex bush that might do