About replacing a buried steam condensate return line

schwec

I recently replaced an aging steam boiler which was consuming a lot of water and had to be filled every 24 to 36 hours. The older automatic water feeder attached to the previous unit did not have a digital read out and it was hard to judge how much water was being used. However, the water feeder attached to the new unit tells me that my new unit has used roughly 85gal in one month. We also turned off the boiler, filled It to the top of the glass and noticed the water level drop to the level of the Hartford loop over a period of 12 hours.

My heating system is a one pipe steam with two mains off the boiler header. The mains run the perimeter of the house and meet at the opposite end of the house. From that point, condensate returns travel downward and run into the ground. The return line emerges 44' away from a concrete slab two feet away from the boiler. The house is 85years old and the condensate return appears to be original to the house. The new boiler is rated for 206k BTU.

I am planning to replace the return and have a couple of questions for this group:
1. Is it okay to use copper for the wet return?
2. The circumference of the existing return line measures 6". Is a 1.5" copper return line adequate?
3. The entire return leg is wet, does it need any pitch towards the boiler?
4. Is it advisable to insulate the return line?
5. Any other considerations?

Jamie Hall

Yes, copper us OK below the waterline.
You could use 1 1/2", but 2" would be better.
No, it doesn't need any pitch, but try to avoid sags.
No need to insulate a return
Do yourself a favour and provide clean out Ts and plugs at the ends...

Abracadabra

schwec said:

....

I am planning to replace the return and have a couple of questions for this group:
1. Is it okay to use copper for the wet return?

..

Along with what Jamie said, I'd suggest sleeving the copper the entire length of the underground run. Just because it's copper, doesn't mean it doesn't corrode.

http://www.copper.org/applications/plumbing/techcorner/prevent_corrosion_cu_tube_buried.html

KC_Jones

Does his new return need to be buried? If it runs along the floor (if it's an unfinished basement) wouldn't that work? That would avoid all that digging and concrete work. I am asking as I do not know, but thought maybe the info would be beneficial to the OP.

Fred

I wouldn't think so, as long as it stays below the water line. I think the OP said it is 44 feet long. That's a pretty good stretch across the floor but if it can hug a wall and not cross any stairs, doorways, etc. it should be OK. I was wondering how successful they might be to dig up an 8 or 10 ft. section of floor and pipe and use the old wet return as a chase to feed the new copper. Probably will need a good flushing first but it could work. Then they could dig right at the point where it emerges 2 feet from the boiler to bring it up and make their connection.

schwec

Thanks for the feedback on my questions.

I'm curious why 2" would be better than 1.5". Based on the existing pipe, I thought the 1.5" copper was closest in size. Why is a larger size preferable for the return?

To answer some of the other points asked.. I'm not planning to dig out and rebury the return line. A portion of the basement is finished and I've gotten a bunch of feedback about not burying the return line. My understanding is that buried lines in concrete are more susceptible to corrosion.

Fortunately, I have a fairly clean way to run the return line around the perimeter of the basement about 12" off the ground without interfering with anything.

I don't think that I can use the existing buried pipe as a chase for new copper because I'm nearly positive it has at least one bend.

Fred

1.5" is fine. It is just that 2" is less likely to get plugged up over time with gunk and is easier to clean/flush out. If you are staying above the floor, you will have good access to clean it out periodically. Put clean-outs on each end of the horizontal.

Jamie Hall

1.5 inch is close enough. I was just being conservative. And your tinling that buried lines are more subject to corrosion If you have a good way to run it and that 12 inch height is beow the Hartford loop, that should do. If you have to drop down at a door, provide a way to drain the low point. Whatever you do, do not go higher than a few inches below the Hartford loop, however.

Shalom

My grandfather did this back in the 80s. Had a leak in a buried wet return, they quoted him a couple thousand dollars to break up the concrete floor and relay the pipe. He decided to do it himself; measured for a run of pipe around the perimeter of the basement along the base of the foundation wall, drilling through interior walls as needed. Had a plumbing supply cut & thread the pipes to his spec, ran them (with the help of a neighborhood guy who worked as an assistant to a real plumber), and built a wooden enclosure to cover them, so it looked like it belonged there. Then he cut the old pipes off flush with the floor. Total expenditure was something like $300, besides what he paid the assistant.

It worked perfectly, with one exception: he didn't know that they grease pipes when they cut/thread them, so he didn't remove the grease. As a result, as soon as he fired up the boiler with all that gunk in the water, the house stank so bad we had to move out for 3 days. I can still remember him unscrewing the vents and pouring vinegar into all the radiators to try and cover up the smell...

(No idea whether he skimmed it or not; I didn't know about such things back then.)

Fred

Anytime new pipe is introduced into a steam system, the boiler will have to be skimmed in a week or two when the oils work their way back to the boiler. If using copper (below the water line) there should be much less oil to deal with since a lot of it is used for pipe threading (not necessary with soldered joints but there may be a little flux). in any case, anticipate one or two boiler skims so don't be alarmed when you see the water in the boiler bounce a lot and maybe even drop to near the bottom of the sight glass. Just skim. Shouldn't be much, if any smell.

Abracadabra

schwec said:

..... My understanding is that buried lines in concrete are more susceptible to corrosion....

That's why I said to sleeve it.

nicholas bonham-carter

Just make sure all of this return is well under the waterline of the boiler, or there will be other waterline problems.--NBC