Copper for condensate pipes? Your opinion

We have used schedule 80 steel on occasion, most often schedule 40 steel, sometimes copper type L or M.

The schedule 80 was used at two schools that suffered from rotted returns on a regular basis. Approximately every five years the four inch welded returns would start to get pitted. After using schedule 40 the first time, we switched to 80. Same results... We decided to modify the piping slightly. The modifications helped, that retutn pipe is fine and now over twenty years old.

Today, we often replace rotted steel returns with copper. To date I cannot recall one failure. However, if it is just a small section of rotted steel pipe we will often use steel again.

If using threaded steel on returns, I definitely prefer cast iron fittings over steel fittings.

Galvanic corrosion could be an issue if the connection to cast iron/steel isn’t buffered by brass/bronze fittings. Providing a swing joint for thermal expansion might be a good idea if the run of copper is long enough.

Better in what way? ('m not challenging you, I just wondered what negative you saw from going copper to steel. Did you see a galvanic issue, or is it just something you are concerned about?)

I did mine in steel just because it was easy and very short but really they should all be copper. The steel grows those corrosion bulge things which accelerates clogging (but it takes years). I can't even imagine a copper return ever clogging…condensate is far cleaner than people realize.

Its a hard thing to predict.

Commercial building that use steam in some cases use higher pressures than the typical 2psi they should use. Higher pressure =higher temperatures. In many cases traps are neglected…….the whole system is neglected.

Due to that steel pipe usually stands up to the abuse better. On commercial jobs it was common to spec #80 for condensate piping.

I have seen old jobs with #40 that lasted for years with just normal issues.

I have also seen 15ps steam jobs where the boiler feed pipe between the pump and the boilers were piped with schedule #40 and it rotted out in 2 years and replaced by schedule #80

Copper is fine for residential.

In my experience the largest factor is the make up water. A job that uses a lot of MU water will rot out fast. If the MU water is kept to minimum things are fine. No surprise I guess.

On commercial jobs the boiler feed piping between the condensate or boiler feed tank and the boiler is always the first to go

Not sure what the code is on this. Your not using copper on HP steam condensate that is for sure. That would never pass inspection.

I have never seen stainless on HP steam unless it was some type of food process boiler or something.

Over the years, I have had a few issues with what seemed to be an electrolysis reaction. I wasnt sure what the cause of corrosion was for certain, but when I used a brass nipple transitioning to copper, most of the time the issues went away. I decided years ago to make it a habit. I had customers to answer to, not to mention a good reputation to maintain. I would sometimes use a brass coupling or even a stainless steel fitting that might have been left over from another job. It just worked (s), and that's good enough for me.

ther's high pressure and then there's high pressure.

@Mad Dog_2 I like the reminder of the 95/5 to 50/50 scenario. I haven't carried 50/50 around for years. I'll have to keep that excellent point in mind for next time.