Pex on steam wet returns?

95nick

  What do you all think about using pex on the returns on 1 pipe steam? 

kcopp

I don't.

200+F degree water in tubing rated for 180F... not good.

Gordan

To be fair

Ratings are for pressure at temp. And there's no pressure to speak of...

Mark Eatherton

PEX at 200 degrees F...

Is like a wet limp noodle. Highly not suggested.



Plastics in general shouldn't be used on steam or condensate systems.



ME

Gordan

You make an excellent point

The issue is not so much bursting (80 psi at 200F rating) as the ability to maintain proper pitch and support itself where it's not supported.

Mark Eatherton

To say nothing of its coefficients of expansion...

It would tie itself into pretzel style knots... Thereby impeding the flow of cendensate.



ME

Gordan

Now what about Pex-Al-Pex?

Significantly better on both grounds (though, obviously, still not rigid.)

Mark Eatherton

Same thing...

Dimensionally, it might be more stable, but I've seen it delaminate with just 180 degree F water.



Its still plastic, and not recommended.



ME

archibald tuttle

what is the up side?

at first blush it sounds like a potentially hand idea in a pinch, says the guy who just replaced all the dies for his 12R handle.



Back before the explosion in copper pricing (and maybe I'd even repeat the feat in this market) ran a 30' piece of copper return in a two pipe system in where the steel had been springing leaks and they were putting cabinets in front of the return so it couldn't be accessed. In theory there are differential expansion issues and I know a lot of folks who won't use it on steam feeds (although I have seen it perform flawlessly in some settings that I inheritted). This copper return is 10 years in and happy.



So what does that prove about Pex.  I take Mark's caution about the material seriously and think the hanging and pipe sizing are critical.  In the larger sizes I'm not sure how much more economical it would be, however if you had a leaking return and needed a quick option to run aways without a lot of fitting and it is in an area that the condition can be monitored it sounds feasible.



But I think the cost and hanging of larger sizes and the reasonable emperical concerns about the actual performance over the long haul of these plastics exposed to extreme end of temperature performance curves make me wonder what is gained.



do you have a particular problem or job you're thinking it might help with?

95nick

Pex

The pex would only be used in short pieces on the vertical pipes. It would be replacing Dresser coupling I put in about 15yrs. ago which have now began leaking. I was going to thread the existing pipe use adapter to pex. Btw, the horizontial part of the returns were replaced already.

Mark Eatherton

I'd rather see you rebuild the sission joint...

They make a teflon rope, or even a roll of conventional graphite packing gland compound that can be substituted for the rubber gasket typically used in this type of joint that could make the joint water/steam tight. That, or thread in a regular ground joint union. (I'm hoping there is a valid reason for having had to use the joint you did already, and I suspect clearance between the pipe and the wall or something else is hte reason for using the slip joint).



ME

95nick

Thanks Mark

I am going to thread the pipes and use uinons. To be honest the only reason I used a Dresser coupling was I didn't know any better!

Mark Eatherton

Understood...

Sometime, when we are in a bind, or short for time, we do what's convenient, and it seems like it ALWAYS comes back to bite us in the hind sight :-)



Good for you for doing the right thing. You'll sleep better knowing that you did.



ME

jumper

I'm lazy & cheap

So I would try repacking coupling.

Or, first try, just goober up those soft compression things.

It doesn't have to hold much pressure.

You can even try sealing leak.