Single pipe steam system return pipe reroute

danmasri

Need to reroute the return pipe coming off the main stack which is blocking the doorway. Contractor feels that if we drop the pipe below the floor and come back up to lower level then we started the water will flow around back to the boiler. I understand that water will always pool in the u shaped drop but if no steam in return to cause knocking should this cause any problem? Trying to slope the return at the top of the doorway will be too low to clear doorway. Any advice or thoughts and experience would be appreciated.

Jamie Hall

A wet return -- that is, a pipe which is and remains below the boiler water level -- can go up or down or sideways as many times as it wants. All that it need do is stay below the boiler water level.

Now that said... the wise plumber will put Ts and plugs where it turns corners, rather than elbows, to make it possible to clean the thing out if and when it needs it.

So -- in this case, if the pipe you are wanting to move is below the boiler water level to begin with, and can be routed to stay that way, you're good.

danmasri

thanks for the information. The return pipe connects below the water line and the end of the return pipe will stay that way. But the portion that is rerouted will be above the water line. Just clarifying that as long as the end is below the waterline this will be fine.

Jamie Hall

No. The portion above the water line will empty and you will have quite an interesting collection of possible problems as a result.

If a return is dry -- that is above the water line, it must stay that way until it drops conclusively below the water line with a vertical drop (and most likely needs a vent on it). If a return is wet -- that is below the water line, it must stay that way.

Is the original pipe -- I presume it's the one with the flagging on it in the middle of the doorway in the picture -- actually a dry return or a wet return? At that middle elevation it could be either.

danmasri

How can I tell? Do I just measure the height and compare to the water line in the boiler?

danmasri

It appears to be 4.5ft high and water level in boiler is a little over 2 ft. This pipe then returns to the boiler along another wall which is not exposed. What problems would I have from going below water level and then coming back up.

EBEBRATT-Ed

We could give better answers.....................not sure which pipe is to be relocated

Jamie Hall

danmasri said:

It appears to be 4.5ft high and water level in boiler is a little over 2 ft. This pipe then returns to the boiler along another wall which is not exposed. What problems would I have from going below water level and then coming back up.

@EBEBRATT-Ed 's comment is quite true. However, on the basis of what I can see and what you have said, the pipe in question is a dry return. How it functions in relation to the rest of the system, however, I can't say. Which is to say what particularly problems you will cause by dropping it down I wouldn't care to list. What I can say is that... just doing that by itself won't work.

It is possible that it might work to drop it down, but put a main vent on it before it drops, but without seeing a plan and profile of all the piping I'm not going to say.

danmasri

The u shaped drop was added with a spigot to drain debris as per your suggestion originally. Original path did not have the U so once going below water level stayed below water level. I spoke to plumber in my area who said it might work. It's the only path to go around doorway. If I get water hammer or other issue will break wall of basement and adjust the remainder of the return line to stay below water level.

Jamie Hall

Been around this barn before. That is not, technically, a return. It is an extension of the steam main. Which means it can be treated differently (and, indeed, needs to be).

You should add a main vent -- if there isn't one already -- to the piping before you drop but preferably after the last radiator runout. If there isn't one there already, adding one will help you heating a lot.

Then -- drop the pipe as needed to get below the door -- and then keep it down. Do NOT bring it back up above the water line.

EBEBRATT-Ed

Yes vent it as @Jamie Hall mentioned and you should be fine. You may have an air bubble at the top of the trap to get rid of

dopey27177

Dropping below the floor to unrestricted access for the door is an excellent idea. Because you are creating a U or trap in the piping you should install a T at both ends of the trap and install a 1/2" pipe going up over the doorway and back down to the other T. This will allow an equalization on both sides of the trap.

This is a cheap installation that can prevent problems though rare where some type of pressurization from the boiler may occur causing water from the boiler to back flow and cause a pressure lock at the trap causing a no flow condition.

This method typically is used where condensate goes below a beam, the jump over equalizes pressures that can occur down stream of the trap.

This is shown on page 50 of my book Steam the Perfect Fluid for Heating and Some of the Problems.

Jake

danmasri

So 1/2" is enough to equalize pressure? I will see if I can add this. Confirming problems are rare if I can't do this? 

I found the main vent covered in foam that was sprayed in wall years ago. Will open back up. I have a 2.5"  main with an approximate 50' run. What main vent/vents should I install. Not sure will have clearance for larger vent like gorton#2 so please help with sizing with multiple #1 or #2 options.

dopey27177

A gorton D vent in my opinion is more than adequate. It vents 4 cubic feet of air in 1 minute, Much cheaper and smaller than a 1 or 2 vent size.

Jake