One-pipe convector - cracked vent tap

hbock

I noticed my bathroom convector has been increasingly noisy this winter. I replaced the vent (1/8" using the side tap), but noticed it was spinning almost freely in the tap. Turns out the tap, which juts out about 1/4", is cracked pretty good in two places. I put lots of tape, screwed it in as far as it would go, and hoped for the best - but it leaks like a sieve. Turned off the supply valve and the leaks have stopped.

Is it a DIY job to replace? It's an ARCO convector, about 26" wide. Unlike traditional radiators, convectors seem hard to find - old or new. It looks like Governale makes one that would be an equivalent replacement. I'd need a 1 1/4" straight union supply valve, some reducers for the venting to go from 3/4"->1/8", and some NPT plugs for the redundant tappings.

AFSupply has one as well (https://www.afsupply.com/cast-iron-convector-element-4-w-x-27-l.html), but they don't give any hints for the tapping sizes or any other useful specs, other than physical size.

Another option I might try, since the supply valve works, is to try and fix it. One idea is to plug up the old tap and open the other 3/4" one on top (my 3 other convectors are set up this way). I'm afraid it won't budge, since it's probably been plugged for 90 years! If I did go this route, would JB-Weld / SteelStik be an option to close up the old tap and cracks? e.g., insert a 1/8" NPT plug, and epoxy around it? Worst case, I have to replace the damn thing anyway.

As you can probably tell, I know enough to be dangerous but not enough to be useful. Let me know if I'm in way over my head!

ethicalpaul

Photos?

hbock

That would be a good idea. Some photos of the convector, the crack, the top tap, and the supply.

ethicalpaul

OK. Honestly I would wrap the vent with a lot of blue tape and put it back in there. Or is it actively leaking from the crack? How high is your operating pressure? I like your floor.

hbock

Cut-out is about 1.25 psi, IIRC. Could probably stand to go lower, I have a vaporstat.

Yeah, it's actively leaking if I were to open the supply. I could put more tape, I only did 4-5 wraps, but I don't think it's going to make it all the way through that crack. Isn't tape more a lubricant than a sealant?

My coworker is suggesting to drill out the end of the crack if I do fill it, since it will just continue to get worse due to the mechanical stress.

Thanks, too bad the floor's going to be ripped out soon. The installers did a poor job (it's only ~10 years old!) and there are nasty cracks and failing grout everywhere.

Jamie Hall

I think -- but with no guarantees -- that I would see if I could use that top tap as the vent location. If I could, then I would -- as your coworker suggests -- drill out the end of the crack -- including the end; it's important that the hole actually includes the real end! -- and fill the hole and crack with JB Weld. And I'd do that in two stages -- first stage, to get a foundation plug on the inside of the hole, and second stage to really get a good seal. Use some force (but not impact) to get the stuff will in there, and cover out to the edges of the boss. Be sure to get all the rust and crud you possibly can off the metal first -- otherwise the epoxy won't adhere.

hbock

Thanks, I appreciate all the quick responses. I'm fine with no guarantees, I've come to terms with that after buying an old house. This convector has lived a very long life and hopefully can be made to live more, but if it has to go, it has to go.

So if I understand your suggestion, the *only* thing filling the hole will be the JB Weld - don't put e.g., a steel NPT plug in first, and fill around that? Perhaps that would only serve to stress the crack more.

EBEBRATT-Ed

I would take it out so you can work on it. Don't take the big plug out, leave it in and drill and tap the big plug 1/8 npt for a new vent

Then you have 2 choices for the crack. grind it down clean it up and JB weld on it or you could take it to a radiator shop or welding shop. I would screw an 1/8" plug in it loosely just to fill the hole and braze it with bronze brazing rod

hbock

My worry about leaving the plug in is there's not a lot of vertical space to put the vent even without it. The square end of the plug subtracts more.

I also like the idea to braze it shut after cleaning it out, but worry flux would be corrosive if it got into the system.

mattmia2

What about brazing a close nipple and coupler or an "extender" in to the hole? i suppose there a re flanges you could braze over the hole as well

Grallert

I think that after a good cleaning and a good smear of JB Weld or something similar you will add many more years to that radiator. I would do the above then wrap a single wrap of tape on the vent and screw it in, don't over tighten. let it set and open the valve. This is a simple repair with no unreversable results. Has worked for me many times. Good luck

hbock

Is a penetrating lubricant/PB blaster a bad idea if it could get inside the convector? My 18" pipe wrench wouldn't budge that top cap (which actually might be 1 1/2". finding reducing bushings is going to be fun, if I ever get there). I have a few mechanical ideas first (cheater bar, bigger pipe wrench, heat...).

mattmia2

you might have to cut/drill that plug and cut a little wedge out almost to the threads to get it loose without breaking something else. Be somewhat careful of where the sections are clamped together with push nipples, enough prying could cause a leak there. the whole thing looks to be rather thin and fragile cast iron as well

mattmia2

you could also try jb welding a nipple and an ell in to the side tape, work the jb weld in to the cracks but don't block the nipple and screw a straight vent in to the ell

hbock

That might be the best idea. Good point about breaking the sections. Maybe I'll use a small metal bit to drill out the point of the cracks, JB in a nipple and an ell. I have a spare hoffman 41 I can use for a straight vent.