Big mouth vent installed horizontally — wrong?

wilder0m · October 19

Hello all. I just had an old Hoffman vent replaced with a Barnes and Jones “big mouth” BJ-B3M. The plumber who installed it moved it about 12” from where the Hoffman was, and also put it on a T. The T comes up from the steam pipe about 8”, then the vent is pointing out horizontally from there. Looking at the spec sheet (https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Barnes-&-Jones-BJ-3BM-Submittal-Sheet.pdf) it looks like only their crossover trap should be installed horizontally; main vents should be installed vertically. Will the horizontal position impact its function or performance? It’s on the dry return about 8” above the pipe. It’s the only vent in the system. 2 pipe steam.

Thanks.

Edit to add picture. The white PVC is open at the bottom leading to a bucket. The gizmo at the very top is a vacuum breaker.

Jamie Hall · October 19

It's on a dry return? Then it shouldn't be a problem — since it should never close anyway.

mattmia2 · October 19

but any water that gets in to it may not find its way back in to the main but may drip out

Jamie Hall · October 19

https://forum.heatinghelp.com/discussion/comment/1868471#Comment_1868471

Quite true. A Big Mouth will not close against water…

EBEBRATT-Ed · October 19

@wilder0m

Can you post some pictures?

109A_5 · October 19

I have a big mouth, oriented correctly very near the end of the main on a 1 pipe system. So it sees steam every boiler cycle. The spec sheet orientation is so the condensation from the steam that closes the valve drains back into the system, minimizing system water loss.

Your system being a 2 pipe system, if your big mouth never sees steam, probably not a big deal.

ethicalpaul · October 20

if the big mouth never sees steam, then it should just be an open pipe. That’s a lot cheaper!

Jamie Hall · October 20

https://forum.heatinghelp.com/discussion/comment/1868515#Comment_1868515

That's the weird little secret of true two pipe steam systems! Putting a vent on what might just as well be an open pipe started when people figured out clever patented widgets to occasionally pressurise the dry return to keep the pressure differential between the returns and the mains to some reasonable value — to keep the water in the boiler where it belongs. (The Hoffman Differential Loop, for instance, was advertised as "The Watchman of the Waterline").

Then people realised that if you put a vent there and steam got into the return from, say, a bad trap then it would close and you didn't get steam in the boiler room and the building super didn't get complaints about steam in the basement. Great! Doesn't help the heating much, but… who cares?

Funny world.

wilder0m · October 21

https://forum.heatinghelp.com/discussion/comment/1868466#Comment_1868466

Yes, on a dry return, however, the old vent was spitting *a lot*, so either steam or water was getting to it somehow. Various problems in my system that might be causing that. I believe my radiators are letting steam into the returns because they have missing or faulty steam traps / orifices. Pressure may be getting too high also.

@mattmia2 @109A_5 @ethicalpaul @Jamie Hall Thanks.

@EBEBRATT-Ed edited to add picture in original post. Thanks.

mattmia2 · October 21

the trap is also a vacuum breaker. be better if the trap were turned 180 degrees so the outlet was facing up so that any condensate in it would run back to the return.

wilder0m · October 21

https://forum.heatinghelp.com/discussion/comment/1868607#Comment_1868607

Right, thanks. But would it be even better for the T to be reconfigured so that the vent is oriented vertically and the outlet is pointing out horizontally? That’s how it’s shown in the spec sheet.

mattmia2 · October 21

i don't think there's much difference between the 2

Jamie Hall · October 21

https://forum.heatinghelp.com/discussion/comment/1868604#Comment_1868604

One thing at a time… you'll get there!

109A_5 · October 21

For best performance regardless of the defects present in the system it should be installed as the spec sheet shows, that is 'Best Practice' in this case. Is there a clearance issue ? Why the plumber install it the wrong way ? Having the vent port pointed up invites debris contamination and I would not suggest that.

109A_5 · October 21

Well just saw the picture. You should not need the PVC pipe leading to a bucket.

I'd figure out why you are experiencing

" the old vent was spitting *a lot*, so either steam or water was getting to it somehow. "

You want to minimize system water consumption, if it is loosing water with every cycle, that is not good. Once that is corrected then correct the Big Mouth vent orientation.

" But would it be even better for the T to be reconfigured "

I would leave the T as is.

I would do this; Disconnect the PVC pipe. Then unscrew the union to disconnect the Big Mouth, unscrew the Big Mouth's spud (requires a Hex tool 5/8" (I think) if it is a 3/4 pipe thread) add a threaded nipple and a 90 degree elbow (preferably brass) pointing up, reinstall the spud and reattach the Big Mouth.

Personally I think the vacuum breaker is kind of useless.

Actually I'd probably just remove the vacuum breaker and put the Big Mouth there if it will fit, then plug the other pipe where the Big Mouth is now.

Big mouth vent installed horizontally — wrong?

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