corroded underground return line

Ehbaseball025 · September 2021

I have a 1 pipe steam system that has a corroded return line that is very brittle. My heating contractor recommended repiping it overhead with copper. I have heard from other contractors that won't work and It needs to be dug up replaced with black pipe and wrapped in foam. Can someone please help.

Jamie Hall · September 2021

Does it go anywhere after that T where it is partly buried? If it's just that short length you have circled, no problem. You can replace that with copper if you like, or with black iron -- take your pick. Don't rebury it, though. In fact, set it an inch or so above the concrete. Neither copper nor iron likes to be in contact with concrete -- that's why it is in such bad shape. I see some handy unions, so it may not be all that hard to do.

Ehbaseball025 · September 2021

it goes from the 2 pipes that connects to a T then down under the concrete for about 12 feet then up to that section that's corroded next to the boiler.

Jamie Hall · September 2021

Replace the whole thing with either copper or black iron, and set it a couple of inches above the floor unless that would make a serious trip hazard.

Ehbaseball025 · September 2021

Jamie Hall said:
Replace the whole thing with either copper or black iron, and set it a couple of inches above the floor unless that would make a serious trip hazard.

yes that will make serious trip hazard and a law suite.

Steamhead · September 2021

I'd use copper underground, wrapped in foam, and backfill the trench with pea gravel to allow ground water to drain away.

Also- that T joint in the last pic needs to be lowered below the boiler's waterline. Otherwise steam can work its way backward thru those pipes, and possibly bang and affect steam distribution.

Last but not least, there appears to be water coming down the back of the boiler. It's probably coming from the chimney, and the whitish color of the tracks is probably sulfur. Have this looked at.

Where are you located?

Ehbaseball025 · September 2021

@Steamhead
The Chimney does need repointing. Is that how the water is running down the boiler? How would the water from the chimney reach the boiler? it's like 4 ft away. Why should the sulfur be looked at? What causing the sulfur on the ground? Im located in CT. Thanks

Steamhead · September 2021

It's probably rain water getting into the chimney, and combining with sulfur deposits therein to form a mild sulfuric acid.

Your system originally had a coal-fired boiler. Coal and (until recently) oil both had high sulfur content, so you'd get sulfur deposits in the chimney. The mild sulfuric acid eats away at mortar joints, which is why it needs repointing.

JUGHNE · September 2021

Is that a patch over where the return line is buried?
If so it would break out pretty easy. And a little dirt digging would give you a new trench.

What ever you bury, I would slip good grade of foam insulation over it, (comes in 6' lengths) with the gravel as Steamhead suggested.

Also a good time to lower that horizontal pipe coming into the tee...well below the water line.

Another idea is if you could run this on the floor around the wall back to the boiler, as long as there are no doorways or if it needs a lot of pipe for this.

Pumpguy · September 2021

If you must keep this underground return line, you might look into using a product called GILSULATE by Gilsulate International. This product, designed specifically for this type of application, is sold as an insulating pour in place material that is hydrophobic, meaning it is non-wetting and therefore prevents corrosion to steel piping.

I have no experience with this product but have been told it is what should be used when buried return lines are the only choice.

Others here on the wall may know of it and be able to comment further.

corroded underground return line

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