Radiator not Heating

mgambuzza

I've been troubleshooting the 22 radiators at my home one (sometimes a few) at a time to get them all working well again. I've gotten down to my last few and was hitting homeruns until the one in a large bedroom. The USR CORP radiator had a vintage Hoffman air valve that seemed a little loose. I went to screw it out and it fell out - not from shear, but because it was stripped so badly they could wedge it back into the radiator. Obviously a new valve won't go in, and during the period it was out for me to take these pictures and wedge it back in, it was heating.

How and what size tap do I need to use to either re-thread, so I can screw a valve back in. Also - at the top offset of the radiator, there is a screw that looks like the valve could either be top mounted or mounted in the middle. Should I try tap and insert the valve in the middle opening, or seal it and place the valve in the upper opening?

EdTheHeaterMan

Tough to see without a reference like a dime or a ruler next to the hole, but the standard pipe size for radiator vents is 1/8" NTP. That pipe size tap is usually a part of the standard SAE Tap and Die set, or you can purchase it separately at ACE or True Value hardware stores, or Auto parts stores that sell tools. The problem is, there may not be enough metal to take the new threads.


You may need to tap and thread a 1/4" NTP pipe opening and install a 1/4" x 1/8" bushing

Steamhead

First, try the 1/8" pipe thread tap. It may just need to have the threads cleaned out.

bburd

Do not use the upper vent tapping on that radiator. That is for hot water systems. If you use it for steam, the radiator is likely to heat only partially.

The only time it should be used for steam is if two vents are needed to get the radiator to heat quickly enough. That way the top vent will close first once the air is out of the riser, and leave the lower vent to fill the radiator more slowly so that steam and condensate don’t clash violently in the piping and cause trouble.

mattmia2

It looks like the threads may have corroded/sheared off that valve, so you might get lucky and might be able to thread a new valve if you clean it up with a tap. It is hard to tell from that picture. Otherwise you will have to drill and tap to 1/4" and use a bushing as @EdTheHeaterMan said.

mgambuzza

I want to thank all for their input on this. After a VERY frustrating search for a 1/8 tap, I easily found a 1/4. Drilled, tapped, screwed, and inserted a leftover Leader air valve, and voila - heat!! Grateful for the advice, and confidence to do this. This was the last radiator to repair and just in time for the sub 20 degree weather.

Jamie Hall

nice work

ethicalpaul

Nice job. I was gonna say Ed was being a little optimistic thinking a 1/8" NPT tap is available at all those places. But it's easily available at Amazon.