Power mains question: wire gauge

Dec 28, 2012 175 Replies

I've seen the pipe fitters install hundreds of feet of black iron on jobs with a lot of air in use such as assembly lines. What is wrong with that? Is it too expensive to install to be cost effective? I have been out of the big job work for over a decade now.

Down here black iron rusts up too fast. They even use galvanized for gas.

Black iron is incredibly expensive and impossible to work with.

It's far harder to do and *more* expensive, particularly if you don't do the threading yourself. Copper is getting expensive but it's still manageable and *simple* to work with.

I bet people are using Pex to carry air these days. Pex is displacing copper pipe for residential water service as well. The plumber installing Pex for part of my circulating hot water heating system commented that if one bids straight copper, one does not win the job.

Joe Gwinn

I thought about using PEX, though wasn't sure if it could take the pressure. A faulty regulator can easily dump 120-200lbs into the system. At least it wouldn't shatter like PVC, though. It's an idea, though I think I already have about half the copper I need for the job. ..though that probably means I'm short 3/4. ;-)

My other house has PEX for its water supply. I have no idea if the house is "normal" but I don't like the stuff. Only one of the outside faucets has any volume and the inside faucets are all weak. It seems there is a lot more pressure/volume lost in the distribution than there is in either the copper systems I've had in the past or the PVC in the new place. One big advantage of PEX for water is temperature stability (someone flushing a john doesn't scald the person taking a shower). Another is the manifold allows one to turn off individual appliances. It's handy for turning off the silcocks in the Winter, though I added ball valves to the distribution system (copper) in my VT house to accomplish pretty much the same thing.

Here is some PEX data:

At 74 F, the rating is 160 psi. The installation proof test is 1.5 times that, or 240 psi. That ought to work.

As for broken regulators, if it's a real problem, I would add a simple overpressure relief valve to handle regulator blowout, protecting more than just the tubing.

Sounds like the installer cheaped out and used too small a diameter of tubing/pipe. This never happens with copper pipe. Never....

Joe Gwinn

Depending on the result, it might be something to worry about. With copper, not so much. PEX probably not, either, but it's failure mode would be important. PVC, absolutely!

I've never seen anything less than 3/4" and 1/2" in homes. Sure, I've seen problems with temperature regulation when they cheaped out but never a supply problem. Even 1/2" was plenty for a hose bib or a kitchen sink. ISTM, that PEX has a *lot* more resistance than copper.

The Romans used lead to carry their water and as a result some developed lead poisoning. Plastic is the new lead.

Rick

Utter nonsense. I'd expect as much, though.

No, idiot. They used a lead acetate compound to sweeten their wine.

The inside of PEX is just as smooth as the inside of copper pipe, and there are usually fewer ells needed with PEX (or copper tubing for that matter). Something else is the matter.

Joe Gwinn

looking on the internet I see lots of installations with what appears to be very fine PEX tubing.

Just to be sure, I pulled out an ohm meter to check it and yup, you're right, PEX has a *lot* more resistance than copper.

Rick

There are NO straight runs, either. Anyway, from my experience, it sucks for water distribution. I'm not all that happy with the PVC I have now, either. Copper is so easy...

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required