Galvanized underground condensate return piping

LSF

An owner with a low pressure steam heating system (40 apartments) wishes to replace his buried underground condensate return piping with galvanized piping. His thought is galvanized may hold up better buried in the ground. Anyone have any thoughts on this? I recommended he stay with black pipe but go to schedule 80.

icesailor

Underground Galvanized:

Galvanized steel pipe is just steel pipe that is dipped in a molten zinc bath. It is sacrificial and will wear off.



A posed question.



I have seen galvanized water services that wee 100+ years old and the inside looked like they were just installed. The same galvanized steel pipe in a similar installation is full of holes and the inside of the pipe is full of plaque. What's the difference in pipe and how is it made? The local water company where I worked had a lot of old Wrought Iron pipe mains in the older parts of their systems with no problems.

ChrisJ

Copper

Not a pro but a lot of guys like to use copper for wet returns. I did all of my own below the water line piping in copper as well while sticking to steel and cast iron above the water line. I am aware of galvanic corrosion and I feel I chose the lesser of the evils.

SWEI

Watch out

for corrosion, especially if you're pouring concrete.  The fly ash which is part of most concrete these days will eat copper.  You'll want coated pipe or sleeves where it's in contact with the concrete or where ground water might be present.



I'd seriously consider using Aquatherm for the underground portion.

ChrisJ

Temperature?

From what I've seen Aquatherm is only rated for up to 200F?

SWEI

Correct

Aquatherm is rated for pressure use up to 200ºF.   Short term exposure to higher temps is part of that calculation.  Commercially-available PP resins melt somewhere north of  265ºF depending on the particular type.



I would not even consider using it on a radiator outlet. At the bottom of a system where the balance of the piping is metallic, I would feel safe specifying it.  An up-front discussion with Aquatherm would be required in order to assure warranty coverage for the job, but based on previous conversations I do not foresee issues as long as the system conditions are similar to what I described.

jumper

galvanized inside

Make sure it isn't galvanized on inside of pipe unless you want ZnOH inside your boiler.

Pumpguy

You might want to look at DriTherm International

They specialize in insulating products for underground piping applications.  They are suitable for temperatures up to 480 and 1250 degrees F, depending on the particular product used.