Ok to put Stainless Tubing in concrete?

McMaster

I read plenty about the PH affects of putting copper and steel in concrete. Is there any issue you are aware of with putting stainless steel tubing in the concrete for purposes of splicing joints? Most splices will be covered with shrink tubing, but I am considering some longer splices where I just put the stainless in the concrete and just heat shrink the ends. By long, none will be longer than 12", most would be in the 6" lengths. It's 304 and I'm machining barbed ends on the stainless like sharkbite fittings.

Thanks

McMaster

Expansion

BTW, before it comes up, I calculated the thermal expansion at 120* T rise:

1" = .00116" 

3" = .0035"

6" = .007"

12"= .014" 

So I don't think small pieces will break the concrete if I encase in heat shrink tubing that has some 'give' to it. But I'm more worried if there would be any ph affects on the SS tubing. My thinking is it should be impervious to the PH.

Your thoughts?

Thanks.

Jean-David Beyer

But I'm more worried if there would be any ph affects on the SS tubing.

I do not know about 305 stainless, and its reactions to pH. But 316 stainless is said react badly to color bleach chemistry in photographic darkrooms. Problem said to be the chlorides in the bleach.



This stuff is mild enough you can put your hands in, though that is not a good idea. The 316 is tough enough if you wash the stuff after each use in an amateur darkroom, but it will not tolerate commercial full-time use.

Paul Pollets

Why??

Why would you use a stainless splice? If you're trying to repair a pinhole in copper tubing within the slab, be prepared for ultimate tubing failure. Levitt systems have a life expectancy. The slab heat will have to be abandoned at some point.

Copper splices should be silver soldered, for longevity and expansion strength

McMaster

clarification

I think you misunderstood my question: I'm repairing and existing PEX system (mine). My question is if there would be any reason to be concerned about 304 stainless in contact with concrete (I can't think of any). Only copper will be the crimp rings, which will be protected by heat shrink. My question is about stainless and concrete.



Thanks

Paul Pollets

Couplings

I'd be using a press fit "pure flow" coupling (Viega) rather than a home-made item. We wrap the splice in 3 mil tape, although it's probably not required. If you don't have the pressfit tool, you'll have to find another method.

McMaster

Here's what they look like

Did not see 3/8" couplers in the Viega PureFlo line.

Here's what one looks like compared to a Sharkbite coupler:

Paul Pollets

Couplings

Viega makes 3/8" and even 5/16" press couplings. I've used the barbed fittings with SS bands. They work OK.

hot_rod

if it is dry

I don't see a problem with stainless in concrete. If moisture is present you might have a problem with corrosion. There are plenty of copper tubes and crimp rings in concrete. The ones that fail are the ones that are wet from ground water, typically.



I put some naked CSST tubing in a concrete radiant sculpture about 20 years ago, still running leak free



I've also worked on 50 year old black iron radiant slab jobs. As long as the pipe is encased in the slab and kept dry, no corrosion.



No doubt a heat shrink sleeve would be a good idea.



Where did you find that stainless coupler? I like the thinner walled look of it. I suspect it could be a much thinner wall than a brass fitting, and had the same or additional strength.

McMaster

Stainless Couplers

Where did you find that stainless coupler? I like the thinner walled look of it.

Thanks for the feedback on your experiences with SS and other tubing in concrete, Hot Rod. The concrete will be dry and I WILL heat-shrink the joints. 

As for the couplers, I milled them out on my mini-lathe. With 3/8" PEX in the slab, I want to preserve as much flow as possible in the repairs. 

 

I didn't know about the Viega couplers, but I think I'll continue down my current path. In some cases I will make 3" and even 6" to bridge the gaps of a few repairs, so I'll probably mill ends on SS tubing as required.



Any other thoughts or suggestions are appreciated...  Thanks,

McMaster 

SWEI

stainless

A couple years back, Wilo told me they were going to build the potable version of one of their new pumps in stainless rather than bronze -- because it was cheaper.



Viega rep told a few months back that thinwall stainless ProPress pipe & fittings frequently cost less than the copper equivalents.

hot_rod

stainless pump volutes

I think all the small re-circ pumps are switching to stainless from brass. I think Grundfos uses a cast stainless? Much thinner and lighter than brass bodies.



I've used some of the Grundfos 15-100 with stainless bodies, a great drainback pump.

Kent_3

leaks

How come your pex developed leaks?

McMaster

It froze

Building was unoccupied for a couple years (upper midwest). The oft touted idea that PEX can't break in concrete, doesn't take into account real world irregularieties such as tubing that may have gotten stepped on during installation and touches the foam board (can break out the bottom where there isn't concrete), or where it's fastened by a zip tie to rebar, and an air bubble might exist under the zip tie. Of course it can freeze by the manifolds too.





The integrety of the tubing, where not frozen, appears to be just fine.

 

Kent_3

OK,

sorry to hear that.  I'm still surprised that it split.  What brand/type (a,b, or c) is it? 

McMaster

PexB

It's Pex B. It stretched quite a bit until it broke, but I guess not enough. I knew before I bought it, there could be problem. We're sorting them out one by one, though. Problem is, there are like 14 zones just in the downstairs alone!