Check valve on condensate return line - failure to close

Fishin_Rod

I am a homeowner with an old two-pipe steam system and no condensate pump.

Recently, I was in the basement near the boiler and heard the main air vent valve start hissing shortly after the burner on the boiler kicked on. I thought, "That's weird, I wonder what is going on?"

I put my hand on the vertical return line, and it was hot all of the way up to the main air vent. I then looked at my configuration and thought, "Dang it, the check valve is being held in the open position."

[Dumb item #1 - I wish I had observed the system running for a few more minutes. I could have then determined if my air vent would have shut off when subjected to enough live steam.]

I turned off the furnace, and came back to disassemble the plumbing when things were cooler. I did find a small amount of debris in the check valve.

My system has two condensate return lines that are plumbed into the Hartford Loop. On the other side of the boiler, there is a manifold that brings three return lines together, and then drops them down to the inlet into the bottom of the boiler reservoir. There is a horizontal brass swing check valve installed at that very low level. It does have a 3/4" valve on either side of the check valve so I can periodically flush the check valve. However, having the valve at this very low level seems like it is located in the place most likely to hold debris.

I have no idea how often my check valve gets stuck in the open position, nor have any idea how many cycles it will remain stuck open before the debris may clear on its own.

I believe this is a horrible efficiency loss? If my steam rate through the condensate return piping is less than the "exhaust rate" on the main air vent valve, then I am wasting live steam into my basement. If my steam rate is greater, then I am wasting live steam, AND no air from my steam supply lines and radiators is being pushed out of the vent on the return side, so therefore very little steam is actually condensing in my radiators.

I assume at some point I will notice the excess humidity in the house? However, our furnace room is located in a separate room from the rest of our basement.

Question:

Would it be wise/worthwhile to install another check valve at a higher elevation in one of the other vertical pipe runs that is still below the main air vent valve? That would kind of make a belt plus suspenders approach to keeping my pants up, and I wanted to see if the experts thought that would be worth the parts plus labor?

Jamie Hall

First question. You mention condensate return lines. Are these lines wet returns, that is located below the water level of the boiler? If not, are the dry returns or are they steam main extensions? That is a critical question. If they are wet returns, it doesn't matter how they are manifolded together. If the are dry returns, then the MUST be connected above the boiler water level — and usually there will be a main vent there. If they are steam main extensions (often mis-named dry returns) the must NOT be connected together above the water line, but drop below it before connecting, and each one may or may not have a main vent.

Now you mention check valves. If your system pressures are under control and there are no condensate return pumps or boiler feed pumps check valves are not required on most systems. There are exceptions, but not many. In general check valves on wet returns are a good deal more trouble than they worth — and if the system pressures and piping are correct they don't do anything anyway.

I am not sure to what you are referring as the "vertical return line". If it is, in fact, a return, it should be cool and likely remain cool or just sort of warm throughout the operation of the boiler. If it is hot, something is not piped correctly. You also mention that it was hot "all the way to the main air vent".

Nope.

Can you either make a drawing showing the piping and relative elevations, or can you take a bunch of photographs which clearly show how the piping is arranged?

Minor things… the vent should shut off immediately when steam reaches it. I suspect yours does, but if it doesn't it's toast and you need to replace it.

You mention steam rate through the condensate piping. If these are wet returns, there is no steam there. If these are true dry returns and there is steam present, somewhere there is a failed trap or the system pressure is excessive and there is a blown water seal. If these are steam main extensions, then the corresponding vent should close. In any of these cases, there should be no "steam rate" or steam flow in a return.

Fishin_Rod

"First question. You mention condensate return lines. Are these lines wet returns, that is located below the water level of the boiler? If not, are the dry returns or are they steam main extensions? That is a critical question. If they are wet returns, it doesn't matter how they are manifolded together. If the are dry returns, then the MUST be connected above the boiler water level — and usually there will be a main vent there. If they are steam main extensions (often mis-named dry returns) the must NOT be connected together above the water line, but drop below it before connecting, and each one may or may not have a main vent."

Newbies talking to experts frequently get the lingo and definitions incorrect.

I thought "dry returns" and "wet returns" referred to different ways that the plumbing of the system was configured. Based on my comprehension of what you just wrote, a "dry return" is the portion of the condensate return line ABOVE the water level in the boiler and the "wet return" is the portion of the same line that is BELOW the water level?

If that is incorrect, please clarify. Because I hate to confuse other newbies that might later read this thread.

For more information for you to address my incorrect terminology: I believe I have a two pipe radiator system. I have valve handles near the top of each radiator on the "live steam" side, and steam traps near the bottom of the radiator on the "condensate return" side. I call all of the lines from the traps onward, the "condensate return pipes". (Please provide the proper term, if there is a more correct descriptor.)

We are lucky to have a very deep basement. The original (coal) boiler was even built into a large sump that is 8" below the floor level of the rest of the basement.

All of the condensate return pipes enter the furnace room near the ceiling. Two lines come in horizontally, and each one has a tee with and turns down in a vertical pipe to connect with my Hartford Loop. There is an air vent valve on the top of each of these tees.

There are then four other condensate return pipes that also enter horizontally near the ceiling and manifold together before the tee and the down vertical to the other side of my furnace. The main air vent valve is at the top of that tee. However, that down vertical is NOT straight down - it has some 90 ells and a lower vertical section before dropping into another down vertical that then ells into the short horizontal run that contains the check valve and enters into the bottom of the boiler inlet.

That side of the furnace also has one "wet return". A condensate return pipe enters along the floor of the furnace room. It then has a riser and enters the return piping (I just described above) a little above the horizontal leg containing the check valve. I have no idea where this return comes from. I can see many of the other returns running just below the ceiling in the other rooms of our basement.

[I apologize for the verbose description. I have a significant hand tremor and can no longer make legible drawings - which would be much clearer for you.]

Further complications: Our original boiler (1918) finally failed about 16 years ago. Everyone recommended the same heating and plumbing company in our city as the only people that still did steam radiator systems. I think they were good plumbers and followed the schematic in the owners manual for our new boiler. However, a whole house system is always more complicated than the plumbing immediately adjacent to the boiler. The new system barely worked at all. They finally had to call an old employee out of retirement to make a bunch of plumbing changes and get the system working. I therefore suspect our steam system plumbing is only "pretty good" and definitely NOT optimal as if it had been installed by steam experts that still installed 20-30 systems per year.

Can you give a quick clarification on lingo? I will then respond to the other questions in your reply in an attempt to keep this thread "readable".

EBEBRATT-Ed

Post some pictures of the piping around the boiler and the air vents etc so we can see what you have.

All we can do is guess at this point.

delcrossv

Your terminology is correct, re. dry vs wet returns. Pictures of your boiler would help determine if it's piped correctly.

Fishin_Rod

My daughter now effectively "owns" my digital camera.

I will get it back from her and post some pictures - since each one is worth a thousand words!

P.S. Is there a forum thread on "how to post pictures" that I can find using the search function? My tech skills are roughly on par with my steam system skills.

Jamie Hall

Well let's see here.

In a two pipe system with traps, such as yours, it's really pretty simple.

You have steam mains. They originate at the boiler header and wander around the place and have runouts and risers to the radiator. They carry steam — and a very small amount of condensate from the pipes themselves (more on that later). They are either main vented (at the distant ends) or are connected to the dry returns through "crossover" traps, which allow air to pass — but not steam.

Then you have dry returns. These usually follow the steam mains pretty closely, and are connected to the radiators through the traps. They carry condensate from the radiators (which really isn't all that much volume), but they also carry the air vented from the radiators. If all the traps are working properly, they never carry steam (or are even much more than warm), and they must be main vented. What you are calling condensate return pipes are, in fact, dry returns.

Then you have wet returns, which are located below the water line of the boiler and are, therefore, always full of water. They will be connected to steam mains or dry returns at any low points in either of those. Those more or less vertical pipes are called drips — and it doesn't matter if they aren't perfectly vertical or even have elbows or whatever in them.

A return is either going to be dry or wet; they can't change one into the other along their routing — if done properly. There is an occasional problem when a new boiler is installed; if its water level is lower than the original, some returns which should be wet become above the water line — and they will give all sorts of problems, depending on where they are located. I am a little concerned given your vey deep basement and the original location of the boiler that one or more of your true wet returns may be above the water line of the boiler. Can you check that?

As I said earlier, unless there is something really weird happening you don't need any of the check valves.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1823727#Comment_1823727

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