Questions on PEX re-piping

[ajs317]

I'm in the process of re-finishing my basement, and so I have access to underneath the entire first floor (but not the second floor). Now that the ceiling is open, I've found a few places where the copper supply piping is corroded (likely from mouse urine) and where there are old gate valves that are seeping very slightly. In addition, many of the supply piping is run underneath the bottom of the floor joists, which requires framing out around them. I'm thinking it might make sense to replace the piping in the basement with PEX, which would also allow it to be configured in a manifold setup. Having not worked with PEX before, I have a couple of questions:

-- Can I run PEX up to the point where the supply goes up through the floor above and then transition into the existing copper piping running to the fixtures? Or is there some disadvantage to a distribution system consisting of PEX tied into runs of copper that might range anywhere to a few feet (for first floor fixtures) to over 10 feet (for piping feeding second floor fixtures)?
-- Assuming that plan works, can I transition to the existing copper a few inches below the first-floor subfloor? If so, are there any tips for safely soldering the fitting onto a pipe that runs up into a wood subfloor? I'm not experienced at all at sweating copper so I'm a little nervous working up in the joist bays.

Thanks in advance.

 

[Reach4]

-- Can I run PEX up to the point where the supply goes up through the floor above and then transition into the existing copper piping running to the fixtures?

Yes.

If so, are there any tips for safely soldering the fitting onto a pipe that runs up into a wood subfloor? I'm not experienced at all at sweating copper so I'm a little nervous working up in the joist bays.

Keep water handy to deal with an unexpected fire.

Are you asking if the heat from the flame hitting the pipe 3 inches from the wood is in danger of conducting up into the flooring and causing damage? I don't think so. You do need to keep the flame from hitting the wood. There are heat shields available if there is any doubt.

I am not a pro. I did not char my wood; a plumber did. However he did not have a few inches of space. The stuff I did was away from the wood.

Make sure the pipe has no water in it. A vertical pipe open on the bottom should not have residual water.

Oatey "tinning flux" is nice.

 

[Sponsor]

 

[ajs317]

Are you asking if the heat from the flame hitting the pipe 3 inches from the wood is in danger of conducting up into the flooring and causing damage? I don't think so. You do need to keep the flame from hitting the wood. There are heat shields available if there is any doubt.

Thanks. Yes, I was concerned about fire safety and heat damage from heat conducting up through the copper pipe. I'm confident that I'll take my time and take care not to let the flame hit wood directly, but some of these stubs are off-center in a 16-inch joist so being a non-pro, I won't have expert control. Luckily none of the spaces are all that tight, other than being up in the joist bay. Maybe I'll look into the heat shield you mention just to be safe.

 

[Reach4]

Some sheet metal would serve I think too. I don't know how thick it would have to be.

 

[Mattsplumbing]

Not sure what type of guard you were referring to, but I’ve had good luck with these. It is impressive how little heat gets through the blanket.

https://www.faucetdepot.com/faucetd...4kPD-eo15fnnxDsVbQStvHM1quh6YF2xoC96cQAvD_BwE

If you’re not comfortable using a torch in joist bays, consider using a Sharkbite coupling as a transition fitting between the copper and PEX. I’ve use them to transition from CPVC whenever possible. For copper, I prefer Propress, but you likely don’t have access to that.

 

[ajs317]

I've looked into using Propress fittings. This manual tool claims to be able to crimp Propress at a small fraction of the cost of the power tool: https://www.amazon.com/IWISS-fittings-Crimping-Propress-Elkhart/dp/B01D177WRC

But the bigger issue is that I want to use ProPEX, and I'm not sure if a suitable coupling is available. Uponor has some literature out there about a newly introduced transition fitting designed for copper crimp, but it doesn't seem to be available at the online supply houses (maybe they could special order it). Between having to deal with the tool and a questionable fitting, I decided it's probably easier to just do the sweat connection.

I'm a little nervous about using a Sharkbite behind a sheetrocked ceiling but it would be easy. I'd love for a bunch of pros on here to tell me I'm being paranoid and everyone they know does this all the time.

 

[Mattsplumbing]

I’ve got the Propress power tool, and it works well, but I would still convert to ProPEX, like you want to do. Much easier to work with. If switching from copper to PEX, I use a Press coupling; one side pressed on the pipe, the other side pressed on a ProPEX male sweat adapter.
If I didn’t have a press tool, or even in places where the tool doesn’t fit, I wouldn’t/don’t hesitate to use a sharkbite coupling. I’ve never had an issue with them. Just be sure you chamfer the outside of the pipe, use inserts for plastic pipe, and mark the pipe to ensure the pipe is pushed in all the way.
As a licensed plumber, I wouldn’t plumb my entire house in sharkbite, but it would be more out of cost than the worry of leaks.

 

[ajs317]

Thanks, very helpful.