3 of 8 Radiators Leaking at Union Nut in a 1-pipe system

SpencerB · April 7

Hi all,

I got such great help here last time that I thought I'd try to lean on the collective experience here again. One-pipe system with a 3-4 year old Burnham/US Boiler rated for 130 MBH or 534 sqft of steam. I calculated an EDR of 311 for my previous post (https://forum.heatinghelp.com/discussion/200276/balance-issues-in-a-single-pipe-system) where everyone helped me fix my venting situation. The issue I'm looking to deal with now is that 3 of the rads leak at or near the union nut. Two upstairs and one downstairs. This only happens when it's below 40 overnight and the steam is running for a long time during the 6am warm-up. In general, my system knocks but not in a dramatic way. So I'm not sure if we're talking about wet steam or just loosened fittings. Either way, we do expect to move out in the next year, so if I can avoid a thousand-dollar repair bill, that'd be great. Having to empty little deli containers every other day or so is a small price to pay to not ruin the floor/ceiling, but it is an inconvenience…

Here is a video (https://drive.google.com/file/d/1GQdOTfGXTCuxKatLXe1zVFPgeVYk9ofn/edit ) showing the most dramatic scenario. In addition to the nut, you can see water coming off the main rad — this is rare and only happens when we leave for a week and turn the temp down to 55-60, so this is not typical. It may just be running under the rad and dripping from that point.

Any questions or ideas are greatly appreciated!

Jamie Hall · April 7

It will either be very simple — or a bear. So might as well try the very simple… what is needed is to recognize that unions are wonderful, but will not tolerate any misalignment, either laterally or vertically — or angularly. The two pipe must be exactly in line. Also, the two faces must be really clean. So — take the union apart (with the heat off!) . Support the feed pipe wo it can't move! Thencheck the faces for foreign material or scratches. Clean them thoroughly. Then do whatever shimming or moving is needed to bring the spud from the radiator exactly in line with the other half of the union. Be fussy. Then I like to take just a bit of dish soap and smear a very thin layer of it on one of the faces. Some folks don't use anything. Then pull the union nut up. Strong hand tight plus no more than half a turn with a wrench should be ample for steam pressures.

You are not using the union nut to pull things together — just to hold them there.

Try that. If that doesn't work, come back…

pecmsg · April 7

A Little never seize on the back of the nut and threads goes a long way.

Steamhead · April 7

I'd simply try tightening the union nuts first. And if that doesn't work, try @Jamie Hall 's suggestion. Worst case is you'll need to replace the valve, including the spud that threads into the radiator.

Larry Weingarten · April 7

Hi, For what it's worth, I like to put just one turn (or a bit more) of the thin teflon tape on the union threads. This lubricates and lets you snug things up a bit more.

Yours, Larry

Jamie Hall · April 7

https://forum.heatinghelp.com/discussion/comment/1893831#Comment_1893831

Um. Try. But be careful to not overtighten the union nuts. They crack very easily — and then you are in trouble! If you are into feeligg torque, 5 to 10 pound-feet is more than enough.

EBEBRATT-Ed · April 7

Unions are funny animals.

I have had 1 1/4, 1 1/2 and 2" unions frozen together that a 2' wrench with a cheater doesn't work. A couple of raps with a hammer will usually get them to break loose very easily.

Same thing works when tightening a leaker. Use some never seize.

If it leaks have someone give it a few taps. You would be surprised the union you think is tight can be tightened more.

3 of 8 Radiators Leaking at Union Nut in a 1-pipe system

Comments

Categories