Re-use black pipe?

PatrickO · October 2020

I have a 1 pipe system with dry returns. Lots of issues that I'm working on and one of the (many, many) solutions I'm tossing around is getting rid of the dry returns and switching to wet.
One reason is because I believe it's ok to use copper for wet returns, correct? That would save a ton of money. The other reason is because I would then have more than enough black pipe taken out to perhaps re-use to change one of my radiator supplies to black pipe as it should be instead of copper which it is now.
Would that be possible?

Robert O'Brien · October 2020

In the scope of the project the cost of black pipe is minute

PatrickO · October 2020

If I'm doing it myself then the cost of black pipe is pretty much my only cost, and at something like $2.50/ft that kind of adds up quick.

JUGHNE · October 2020

If you read much here you will find that wet returns are a curse for many people with older systems.
Especially if buried under the floor.
Wet returns tend to sludge up as they are always full of water.
Flushing is recommended every few years.

You would have to relocate your main air vents to the end of the steam mains just before the drop into the wet return.

Would you bury the wet return piping?

PatrickO · October 2020

Considering I only have 2 non-working main vents (big mouth's on order) that's not too much of an issue.
I wouldn't bury, just run along the basement floor.

Jamie Hall · October 2020

It certainly is feasible. Are your steam mains parallel flow? I presume so, since you are referencing dry returns -- by which I presume you mean that the steam pipe continues on back to the boiler. No traps between the steam mains and the dry returns, and the dry returns do not pick up returns from any two pipe radiators...

If you do go to wet returns, be sure that you create some handy way, such as plugged Ts, to flush them out.

mattmia2 · October 2020

I think the cost of large diameter copper and iron pipe and fittings are comparable...

Steamhead · October 2020

If the iron pipe is in good shape- not rusted or pitted inside- it could probably be re-used in the way you describe. But inspect it carefully to be sure, you don't want to have to replace it in a few years.

And yes, run your new copper wet returns a few inches above floor level and provide a drain for flushing.

Are the existing dry returns in the way, for example where people can bang their heads on them?

MaxMercy · October 2020

I'm not a pro, but when I replaced my boiler at home three years ago, the plan was to reuse the black pipe, and my brother and I using two huge pipe wrenches couldn't budge it, even with heat. Instead of taking the whole day trying to reuse the old pipe, I measured what I needed and had the local plumbing supply cut and thread everything I needed. Time is money, plus there were no leaks to deal with.

nicholas bonham-carter · October 2020

You could save some money, reusing the elbows, tee's, and couplings.--NBC

Re-use black pipe?

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