Copper-to-PEX transition below floor surface or PEX-in-Attic re-pipe?

[pollymath]

I've got a daisy-chained copper setup in my on-slab master bathroom that I'm remodelling.

The 3/4" pipe comes from the manifold at the hot water heater approximately 10' away. It then branches, above the slab, with a 1/2" line to the garage sink, about 7' away.

The problem is that this 3/4 and 1/2 setup is right in the middle of my bathroom, right where my future shower door will be. Four pipes total, with a reducing tee on the 3/4" lines, then an elbow onto the 1/2" line.

- I cannot bend them enough to get them into the wall, 12" away.
- If I put a transition fitting on them, I'll still need fittings below the floor surface, and I'll need to cover such a void in a way that could be tiled over.
- If I transition them under the slab to PEX, I'll still need to run the PEX over the wall and through the bottom plate.
- As a novice copper sweater, I'm not confident in my ability to make these transitions. I could, in theory, cut off the existing tee/elbow combination and use couplers to sink the whole setup below the floor level, then transition to PEX above. That'd limit the number of connections.

- If I hire a plumber to do this, it's doubtful I'll be able to find someone to braze these connections especially below the slab. I'll have to work with a void in the slab either way, and routing the PEX over to the wall via a shallow "trough".

- My hot water heater and mechanical closet is 10' away, and I live on a single story slab house where my 1" main water line feed has survived 22 years without freezing. PEX seems like the easy button.

 

[Breplum]

1. To meet code, any under-slab connections must be brazed/silver soldered.
2. Most jurisdictions allow Viega ProPress connections under slab now, and we've been doing it that way for a decade. I even have a Viega print out that states that it is allowed.
I do not think copper to PEX under the slab is the best way to go (and not code approved). I would use the PRoPress to PEX adapters and sleeve the section for protection with a piece of PVC Sch 40 pipe. But would rather do all copper pressed until out of the slab.

 

[Sponsor]

 

[Jeff H Young]

1. To meet code, any under-slab connections must be brazed/silver soldered.
2. Most jurisdictions allow Viega ProPress connections under slab now, and we've been doing it that way for a decade. I even have a Viega print out that states that it is allowed.
I do not think copper to PEX under the slab is the best way to go (and not code approved). I would use the PRoPress to PEX adapters and sleeve the section for protection with a piece of PVC Sch 40 pipe. But would rather do all copper pressed until out of the slab.

that is a lot easier than brazing makes things easy didnt know pro press takes place of braze joints underground

 

[pollymath]

So if understand you, you'd advocate for copper-to-copper via Viega ProPress until above the floor (in the wall) then switch to PEX in the wall.

To minimize fittings, I'd probably extend the 1/2" and 3/4" pipes the whole way to the wall, then tie them together.

I'm not wild about trenching to the wall and through the bottom plate but at least it's not far.

 

[Jeff H Young]

not fully following you but why not run overhead for 10 foot and eliminate the underground lines? Im not advocating or putting down running pex any where but if you have pex thats working for you then why mess with it? I think your question is for breplumb but thats some of my though on it. good luck!

 

[pollymath]

Running PEX overhead would require tearing apart the existing copper manifold in the mechanical room, which doesn't have great access (I actually have to access it from the bathroom via drywall removal.)

I'm still trying to determine the pros and cons of each approach.

My mechanical closet is packed full of copper, but I'm going to need to replace two water heaters in the near future: a 55gal DHW and 55gal Commercial HWH for my hydronic system. Going to PEX would allow me more DIY customization if I want to go to a dual-loop wall mounted boiler in the garage or something.