Dry return lines piped together

Bill Price H.W. price and Sons, Inc. Heating/Air C

I was at a home yesterday that has been experiencing steam heat problems, ie. overheating, banging, make-up water problems, etc.
I found that the two steam supply mains are pitched away from the boiler and at the end of each main the vents are installed properly, but the condensate than drops into separate dry return lines.However, after they drop, someone tied the two together, well above boiler water level, and than the two pipes form one dry return back to the boiler. It is apparent that steam is pushing from one steam main into the other via this cross connection, since it is a dry return with no water trap. My questions are:
(1) Is this right?
(2) Is it correct to assume that both of these dry returns should be separated and than piped back to boiler below water level?
Please reply, and thanks for your help in advance!

patrick linhardt

you are on to something

Hi Bill,

You are correct, the steam mains are cross connected at the dry return connection. It is always good steam piping practice to keep these end of mains trapped separately. When I say trapped, it is with the water seal of the wet return (waterline of the boiler at rest), rather than a steam trap.

I would start with this repair first, since it could be the source of your problems and we know it is wrong. However, there could be more things wrong with this system.

How steady is the waterline? Are you seeing any water dripping down from the top of the gauge glass? If so, this is an indication of oil on the waterline. A good skimming or cleaning would then be necessary.

How clear is the existing wet return? Many make-up water problems are commonly caused by a clogged wet return.

Is the thermostat's heat anticipator set correctly? If not, this can cause overheating.

When does the water hammer occur, at the start, middle or end of the boielr cycle? When it happens can help us understand why it happens.

Can you tell us more about the system, one or two pipe, size, etc.?

Best regards, Pat

Steamhead (in transit)

You're right, that's wrong

There are three ways to get around this. One is to run two separate dry returns back to the boiler room and drop them below water level before they connect. Two, you could change the dry return to a wet return and have both mains drip below water level before connecting to the wet return.

If the previous two would be impractical, you could build a water seal between the two dry returns. One dry return would continue to the boiler room unobstructed as it does now. This makes sure you have leftover steam pressure all the way back to the drip, maintaining your "A" Dimension. The other would discharge into a water seal before connecting to the first dry return. This insures that steam cannot flow between the two returns.

The water seal is a U-shaped pipe which should be as deep as possible. I like to make these seals at least five feet deep. Put a boiler drain in the bottom so you can drain or flush out the seal if needed. Fill the seal with water before starting up the system, or it will bang until it fills.

Here's a pic of a seal that Tom "thfurnitureguy" built. The two dry returns come in from the right (they're actually the very ends of the steam mains, you can see the "trees" of Gorton #2 main vents on top of them), one goes thru the seal, then the condensate continues to the boiler thru the pipe on the left, which drips into a wet return in the boiler room.

Bill Price H.W. price and Sons, Inc. Heating/Air C

More on this system/Here's more info

I appreciate the quick response!
Apparently the previous owner had a large double door installed in the basement on grade, and when they did, they removed the dry return line from one main and instead of rerouting, they just tied it into the other main's dry return. The problem is the main ends on the other side of the basement, and to carry this line(s) back to wet return we will have to run approx. 60' 1 1/2" pipe.
The homeowner may be receptive to this , since the price of natural gas will skyrocket here shortly in the NorthEast, so any dollar spent to improve his system will certainly be well spent.
Also, the entire supply system has been stripped of it's pipe insulation, and I remember a Holahan topic on how the steam is condensing back to water, and than some radiators wouldn't get hot.I am recommending that the steam mains be insulated, and that we run a wet return at/from the point of the steam main drops, and tie both dry returns in BELOW boiler water level, which should prevent backfeed from one main to another.
What do you think? thanks for your help!

Bill Price H.W. price and Sons, Inc. Heating/Air C

Waterseal method

Steamhead...IS that your real name! (LOL)
Thanks for the info and the pic...I appreciate the fast response, and also your consideration to my problem. I am going to save this place on my "Favorites", because there is certainly a wealth of info here!
I will bounce this info off the owner, and let him decide on which way to go...cost effective (Wet Seal), or run new wet return around perimeter to boiler Hartford.(Ex-pensive)
Thanks again, SteamHead...

Steamhead (in transit)

If you use a water seal

and the basement is finished, you must leave access to the seal to drain or flush it- the same way you would leave access to the main vents.

No, my name's Frank- but when I first came to the Wall, there were several other Franks here so I thought I'd do something different. Steam heating is my thing, so I became Steamhead.

Bill Price H.W. price and Sons, Inc. Heating/Air C

SteamHead

SteamHead (er,Frank):

Thanks for your help. I thought I knew what was wrong with that piping arrangement, but NOW I know it was wrong.
I'll keep you posted as to how we make out.
Thanks again!

jackchips_2

A couple of

things, Bill.

1) Please be sure to follow up and let us all know what happened. Following Pat's and Steamheads advice will give you great success and those of us in the background enjoy hearing the outcome.

2) Seeing as your new here, welcome and as a suggestion, especially when you reach a positive conclusion to your problem, hit that symbol at the top that says put a brick in the wall and help keep this site going. You'll feel good after doing it.

Thanks and again, welcome,

Jack