Swing Joint on steam main

Gateacre

Hey everyone. I'm thinking that I may need to rebuild this crossover assembly as well rebuild the F&T. The main is 5" for most of its ~70' length and 4" for the last ~30'. One of the 3/4 nipples is leaking slightly at the threads and others don't look so hot. I don't know how long the flex hose has been part of the design but I know it's been replaced a few times I wonder if a threaded swing joint would be a more robust option for expansion control. Space isn't a concern.

delcrossv

Yes, a swing would be better. Just make sure you maintain pitch away from the trap

EdTheHeaterMan

Is this high spot a problem? Or is this high spot low enough below the trap to drain properly?

Gateacre

Good point. My thought is that the flex will lie flat when the main expands and pulls it taut. This photo was taken when the pipe was cool but I should look again when it's hot to see if that's the case. The trap is not functioning and the strainer is blocked so currently, nothing is getting through there anyway. I honestly don't know when the last time it worked was.

EdTheHeaterMan

This might be a better design, just keep everything sloping back to the boiler return.

Or perhaps a different trap will work.

Gateacre

https://forum.heatinghelp.com/discussion/comment/1827979#Comment_1827979

Wow. Thank you. You've just set off a light bulb for me, I think. It's hard to see in the photo but there are two 90s and a close nipple creating a slight offset in the discharge from the trap. They blend in with the drip leg behind them. I wonder if their purpose was to allow the trap to rotate slightly around its inlet connection and accommodate extension. If so, the flex hose (certainly not original to the system) is just preventing the swing joint from working.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1828017#Comment_1828017

Needs to be offset from the axis of expansion. Like @EdTheHeaterMan 's.

EBEBRATT-Ed

So your steam main is 100 feet long and it's going to expand a lot going from say 50 or 60 deg to 212. The pipe can expand in length about 1 3/8" depending on hangers/anchors

Yes you need swing joints. The condensate return will also heat up but not as much as the steam so you will still have a lot of expansion between the two

When you come out of the tee you have a union and then a 90. Where the 90 is you need the swing joint there. Turn the existing 90 down then put a close nipple and another 90.

That is the only way to keep the trap from pulling on the flex.

Gateacre

https://forum.heatinghelp.com/discussion/comment/1828044#Comment_1828044

Ok. I just want to make sure I'm clear on this (I'm not a plumber or pipe fitter, just enthusiastic and charged with maintaining this old building). Are you saying I need a swing joint at both ends of the crossover (the section with the valve and strainer). Phrased another way: a pivot point in line with the ends of both the main and the return so that the whole assembly can 'rack' as the main lengthens relative to the return? This makes sense to me as it would seem to greatly reduce the strain on that first 3/4" elbow (on all the 3/4 pipe really). So… assuming I'm correct so far, is this sufficient? Bearing in mind that I'd like to get rid of the flex hose, are these two points of rotation adequate or would I still need something like Ed drew? Essentially a small section after the trap outlet that can 'unfold' and allow the return side to lengthen.

I really appreciate everyone's guidance on this.

delcrossv

If I were doing it, I'd use 4. Trap to street going down , street to 90 , to short nipple transverse to long pipe to street going down, street to 90 to long pipe.

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1828044#Comment_1828044

I have to assume the main isn't 100 feet in a straight line. So some of that expansion is going to be a lateral direction, not as big a deal.

And I have to think that at least some of it is in 180 degree opposition, canceling out some of the expansion. Even in my tiny system the boiler is in the center and the main makes 4 turns becoming a rectangle shape so any expansion is almost completely offset in both axes

Gateacre

https://forum.heatinghelp.com/discussion/comment/1828140#Comment_1828140

Ok, that's what I thought. I'll need to raise the 2" Tee to keep things pitched properly. Thanks for your help.

Gateacre

https://forum.heatinghelp.com/discussion/comment/1828143#Comment_1828143

Actually it is just a straight run with the exception of 1 small rise in elevation of about 6 inches.

The boiler is in line with the border of the yellow and red buildings at the far right and the line ends in the basement below the sidewalk of the second storefront.

ethicalpaul

Gnarly. It makes me like the flex line!