Replacing 100 year old wet return

stevenknaub

I have a low pressure steam system with 100% black piping. My wet return is very rusty and likely somewhat clogged and I want to replace it. Is it acceptable to use copper tubing instead of black pipe? Will copper cause corrosion anywhere? Also, the wet return drops down from the main about 4 feet, then runs horizontal for about 20 feet, then drops down to floor level and runs another 20 feet to the boiler, where it attaches to the Hartford Loop. I would like to run the whole wet return sloped in a straight line from the first drop, instead of running it at floor level, would this be harmful? This would keep the piping away from the floor and eliminate extra bends. I would still attach the return where it is attached now.

Fred

You can use copper in a wet return, below the boiler water line. The temps will never get hot enough to cause a lot of expansion/contraction, the most likely cause for failure, at the solder joints above the water line.
You can run the horizontal return at one level, as long as it stays well below the boiler normal water line and it doesn't have to have any slope towards the boiler. It will be filled with water up to the Boiler water level anyway.

New England SteamWorks

It's probably all right, -but why take the chance? Dissimilar metals always set up galvanic corrosion, and cast iron (your boiler) will always lose to copper.

EBEBRATT-Ed

Copper is ok, just don't use it above the waterline. You don't have to pitch it but for ease of cleaning you may want to (someday) put a tee with a cleanout on each end so you can flush it with a hose

Jamie Hall

All of the above, and re-emphasizing the point of keeping the high end solidly below the water line in the boiler. In fact, it really has to be below the level of the low water cutoff. Is that four foot drop you mention really enough?

nicholas bonham-carter

You should always put a brass or bronze transition piece (even a ball valve), between the iron and copper.
Do not think about using the so-called dialectric fittings, which will give you many leaks.—NBC

the_donut

If you don’t have any leaks, and the pipe isn’t rotten you could try flushing out line or gently augering it without tip.

gerry gill

Many guys use copper for return pipes even tho there is a galvanic cell created. We generally use black but if it goes underground we to will switch to copper for that section. NBC is correct in what ever you do, don't use a dielectric union on a steam condensate system. Temps are to high and it will eventually leak. Saw a dielectric union ruin a 1 year old boiler that way once.

stevenknaub

I replaced the return with black pipe. for the first time since I can't remember, the water line remains stable. This may be the first season I don't have to add water two times per month! Almost certainly I had a leaking return but couldn't see the leak

EBEBRATT-Ed

It was probably leaking under the floor where it couldn't be seen