Big Mouth vent not closing

Dave_61

We are losing about ½-¾” of water in our sight glass per week. I went around and checked radiators etc and didn’t find anything major. Today, I went down to the basement with boiler running and found one of our 3 big mouths making noise. Two are completely closed but one is definitely making noise, and it’s damp inside the opening. The main is hot. Is there anything to do besides replace it as they’re expensive. It’s probably 3 years old. Thanks 

Long Beach Ed

Call them. They'll help you out.

ethicalpaul

Yeah this is a known fail point I guess especially among the early ones. I took mine out of service, anyone want it, cut you a deal

STEAM DOCTOR

I had many leakers. Some of the early ones, some of the mid generations, some of the later ones. Leak rate was way too high so I stopped using them.

gfrbrookline

I have six on my system, three on each main. One stopped closing about five years ago, they replaced it no questions asked. I haven't had an issue since it was replaced. Still love the venting capacity of these things, much better that a tree of 6 Gortons on each main.

Mad Dog_2

I had good success with them - no leaders but thats been about 3 years.  You could always get replacement capsules and easilt change them. This Old House is ready for some replacements for the Gorton #2 batteries after 22 years. Ill test drive the Big Mouth vents and let you'll know.  The one thing I suggest is directing any spitting condensate downward with a nipple & elbow facing down so you don't get sprayed with scalding condensate.   Mad 🐕 Dog

Neild5

I have 8 Big Mouths on our system,  3 started leaking not long after I got them, they were some of the early units.  I opened them up and the o-ring seal had failed, it looked like the rubber had melted.  I replaced the o-rings with hi-temp o-rings and have not had anymore leaks.

Jamie Hall

One thing to remember about Big Mouths -- they are not intended to close against water at all, unlike most other vents. They are temperature sensitive only -- so if there is any water in the area, they can and will spit or even burp...

Waher

It might have been @New England SteamWorks , but some pro on the forum stated that when they used Big Mouths in lieu of Gorton No.5 vents they were mounting them ~12"+ above mains to help avoid issues with water being ejected.

JUGHNE

These Big Mouths were added on an unused steam drop from an express down feed attic riser, near the EOM.
The idea was that the "dry " returns had become wet and would not vent the main.

Usually you would not put air vents in a classroom, but there was no way to the attic.

After a few years of use the wall paint suffered a little, (building to be demoed soon).

Even with this much riser there was still a little spitting.
The ball valve was added in line in the event the vent really passed water.

I did this in two other places in the building with similar results.
But the system worked much better with the vents.

Dave_61

This wasn’t ejecting water. It was just hissing constantly. This vent was on a loop off the boiler (like an elongated U on its side). The supply is 2” and it loops to a 1” steel pipe that returns to the boiler. The Big Mouth is mounted about a foot above 1”:pipe. Each leg of the loop is about 20-25 feet long. .I replaced the Big Mouth with a #1 Maid o’Mist. Is that sufficient for the loop in question or would I be better off with a bigger vent? By the way, no more hissing and water level on boiler is now stable. Thanks

bmma

I had a similar problem with the Big Mouth. The company was great to deal with, they were very responsive and willing to help me out any way they could but after my third failing vent, I switched to Gorton #2s.

Dave_61

bmma said:

I had a similar problem with the Big Mouth. The company was great to deal with, they were very responsive and willing to help me out any way they could but after my third failing vent, I switched to Gorton #2s.

I'll give them a call. Right now, in order to decrease my steam loss, I replaced the Big Mouth with a Maid O Mist #1. Based on the steam loop in my above entry, is it adequate for now? I see at 3 oz pressure, the Big Mouth vents 3.6 CFM. What is the venting capacity of the MOM vent? Thanks

ethicalpaul

The venting capacity charts are imperfect. What really matters is if the vent is venting fast enough for your particular main in most situations

Since you are handy enough to remove and replace vents, just do this easy test:

Interrupt your boiler in the middle of a call for heat. Leave it off for some minutes. Power it back on and time how long it takes for steam to close your main vent (in your case, the currently-installed #1). If it doesn't take very long, you are fine. If you want, you can do the same test with no vent at all installed to compare times. I think you'll find the times aren't that different.

One thing to remember is, as a main cools (even an insulated one), on the next call for heat, the steam will move slower on startup the cooler the main is, because the steam is getting "used up" by re-heating the main to about 212F.

This means even a single #1 vent can really do an outstanding job of letting all the air out as the steam re-heats the main, even if its capacity seems not large enough according to some chart.

Dave_61

ethicalpaul said:

The venting capacity charts are imperfect. What really matters is if the vent is venting fast enough for your particular main in most situations

Since you are handy enough to remove and replace vents, just do this easy test:

Interrupt your boiler in the middle of a call for heat. Leave it off for some minutes. Power it back on and time how long it takes for steam to close your main vent (in your case, the currently-installed #1). If it doesn't take very long, you are fine. If you want, you can do the same test with no vent at all installed to compare times. I think you'll find the times aren't that different.

One thing to remember is, as a main cools (even an insulated one), on the next call for heat, the steam will move slower on startup the cooler the main is, because the steam is getting "used up" by re-heating the main to about 212F.

This means even a single #1 vent can really do an outstanding job of letting all the air out as the steam re-heats the main, even if its capacity seems not large enough according to some chart.

Thanks Paul. Looks like I have a little experimenting to do! I haven't noticed any significant difference in the balance of the heat in the house with the new #1 installed. This loop in question supplies a wing of the house. The wing has been as warm as the rest of the house and seems to heat at the same rate even since I replaced the BM with the MOM

Dave_61

One further question. We are going away for a couple weeks and I wanted to top off our water level so we don’t have any issues with the super cold weather. 

Our boiler is a Weil McLain SGO5. I pushed the button on the VXT feeder and added about an inch of water to the sight glass. It took 20 seconds. What would we be talking about in volume? A gallon or so? The feeder has not had to add any water in several weeks but our level had dropped about ½” with heat on. Thanks 

Long Beach Ed

The VXT's are generally set up to feed at 1 gallon per minute. Fifteen seconds would feed about a quart.
The SGO-5 steam boiler contains 14.2 gallons of water, to the water line.

Here's the VXT installation instructions:
https://hydrolevel.com/wp-content/uploads/2021/06/VXT-24-Instructions-web-0321.pdf

Dave_61

Long Beach Ed said:

The VXT's are generally set up to feed at 1 gallon per minute. Fifteen seconds would feed about a quart.
The SGO-5 steam boiler contains 14.2 gallons of water, to the water line.

Here's the VXT installation instructions:
https://hydrolevel.com/wp-content/uploads/2021/06/VXT-24-Instructions-web-0321.pdf

Thanks Ed. Is the water line you refer to the line stamped on the boiler jacket? The distance between that stamped line and where my LWCO probe is is only about 1.5”. You’d think the probe would be placed lower than that.

Long Beach Ed

The standing water line on your boiler is 26-7/8" off the floor pad, which is where it should be stamped. They don't specify a minimum line or operating range, though the minimum is usually at the bottom of the sight glass. You may wish to call them to confirm the range. The tapping for the low water cutoff appears to be quite high. That's their design, which seems to give you a 3" operating range, which is not unheard of.

A loss of 1/2" of water weekly is not unreasonable, but you may want to check your system for steam leaks at the radiator valve stems and sight glass washers. You may be able to tighten it up.

Checking and adjusting the water line weekly in a residential steam system is normal and expected during heating season.

ethicalpaul

I think a loss of 1/2" per week is unreasonable.

As for how much water it is, what I did was stick a length of masking tape next to my gauge glass, then I drained the boiler to near the bottom of the glass, then I added 1 quart of water at a time and marked the level after each one. My skim port is set up with a permanently installed valve so I can add water or chemicals easily at will.

Now my boiler is very small and 1 quart of water raised the water level about 1/4" on the glass.

If you have a large boiler you might add a gallon or 1/2 gallon at a time in order to be able to measure the difference on the glass.

I don't believe in auto-feeders. Steam homeowners should be looking at their boiler once a week during the heating season to be familiar with how much water it is using and adding makeup water manually.

Gsmith

I completely agree re the auto feeder and weekly checking. We don’t expect our refrigerators to automatically refill themselves with food, or our cars with fuel. But, I admit it’s a little problem if you live in a cold climate and travel away from home for any appreciable time in the winter.

ethicalpaul

Is "a couple weeks" appreciable? If it's more someone should be checking on it (or a wifi thermometer)

Ironman

“Big Mouth not Closing”

At first, I thought this post was about The View.

mattmia2

ethicalpaul said:

As for how much water it is, what I did was stick a length of masking tape next to my gauge glass, then I drained the boiler to near the bottom of the glass, then I added 1 quart of water at a time and marked the level after each one. My skim port is set up with a permanently installed valve so I can add water or chemicals easily at will.

It would be a lot easier to measure as you remove it than to measure as you are adding it.

ethicalpaul

I think you're right--I had a reason for doing it that way but I can't remember it now

Dave_61

I do check it every few days when we are at the house, but we are sometimes not there for a week or 2. Since I replaced the Big Mouth with a Maid O'Mist #1, we have used 1 gallon in about a month. At least, that's what autofeed says. I have had no luck with Barnes &Jones regarding replacing Big Mouth and don't want to spend $125 for a new one. I purchased some o-rings red high temp and am thinking I have nothing to lose replacing the o-ring. I also purchased some red JB weld 31314 to secure o-ring. We'll see how it goes.

Dave_61

Just an update in case anyone wants to try to repair their Big Mouth vent. I opened it and saw nothing obvious except evidence of water inside and running down the outlet in the past. I removed the old oring and replaced with a silicone hi temp replacement along with high temp JB weld to secure it in place. I let it cure for a day or two and reassembled it. So far I feel no steam leakage when the vent is nice and hot. I previously could hear a hissing and feel steam coming out. The bellows did sound like it had liquid inside when I had the vent open. Hope this helps others.

Waher

I wouldn't have used JB Weld. That's going to be difficult to impossible to take apart again.

mattmia2

The bellows are partly filled with some type of alcohol that boils and expands and closes the bellows.

Dave_61

Waher said:

I wouldn't have used JB Weld. That's going to be difficult to impossible to take apart again.

Just their gasket material. Used a few drops on the small oring to hold it in place. Not on vent itself. 

109A_5

Hello @Dave_61,
My Big Mouth came with the O-Ring not properly seated in the grove, you could see it through the inlet port. I believe it would not work correctly as received. I emailed B & J, no response. I hate to return things. So I just bought some used sockets and took it apart (I did not want to use pipe wrenches).
Once the O-Ring is properly installed in the grove it is very hard to get back out.
Additionally, measuring the groove and the O-Ring (curiosity and for future maintenance purposes) I believe the O-Ring B & J chose is actually one size down from the groove dimensions thus aiding to it staying in place with a little elasticity of the ID (Inner Diameter) of the O-Ring.
Since over the years I believe B & J has had various revisions to this product, so others may be different than mine.