Laying water return line on top of framing for ceiling (CPVC or PEX)?

[Squeak]

I am in the process of looking at a tankless water heater with a built in recirc pump. I would love to have a dedicated return line for the recirculation, as the heater (Rinnai RUR98i) provides better control with that, versus a crossover.

The outlet furthest away from my heater would be the kitchen sink.

Bad news: My basement is finished with a drywall ceiling, and this line being run would include having to travel about 20 feet in this "finished space"

Good news: The way my basement was built, I have a straight shot in a "plenum" space between my unfinished mechanical room, and where the connection would need to be. Even better, I put in a access panel where the tie in to the kitchen would be, because the shutoff for the ice maker is there.

It would be very easy to run a piece of CPVC or PEX in the space, and be able to make a connection at the access panel.

However....short of having to create more access panels, I would not be able to strap it down for the length of the run, except at the beginning, and at the end. It would have to sit upon the framing members for the ceiling.

Pictures:

1) Access panel at the end of the run

2) Looking from my unfinished utility space down the "plenum" (Note the white PVC pipe hanging as a reference -- that is actually something I ran to fish wires into an interior finished room in the basement. It is not for plumbing at all)

3) Same "plenum" but now looking from the access panel back. Might be hard to tell, but about halfway though this run, the space narrows to only about 6" wide due to beams.

As you can see, getting a pipe through there would not be tough, but it would just be laying on the framing members for that run.

How big of a deal would it be to run this return line in this space without strapping it down? I know it is not ideal, but is it "sort of bad", or "really stupid because of X, Y and Z"?

Better to use PEX or CPVC for this run (current water is all CPVC)? I could also run 1.5" gray PVC as a "conduit" for it to get some rigidity, and run the 1/2" CPVC inside of that until meets the connection.

Thanks!

 

[sirbOOmdotcom]

I would personally have no problem fishing PEX through there so long as it is one single run without a single joint in the pictured area. But I might opt to put hot water pipe foam around it so it doesn't make any noise in the event it moves about.

 

[Sponsor]

 

[Squeak]

I would personally have no problem fishing PEX through there so long as it is one single run without a single joint in the pictured area. But I might opt to put hot water pipe foam around it so it doesn't make any noise in the event it moves about.

Oh, great point...no joints at all in there -- the only joint would be when it hits the water heater. Putting insulation around it to both help with heat loss, and noise, is a great idea.

 

[sirbOOmdotcom]

Not CVPC. That's for trailer homes and, evidently, most of Florida. No offense.

 

[DaveHo]

Do you have enough room to get lengths of PVC pipe up there? If so, you could run the PEX inside that. I see what looks like a nail poking through the sheetrock. PVC would give it some protection.

 

[Squeak]

Not CVPC. That's for trailer homes and, evidently, most of Florida. No offense.

Ha! Well I don't live in a trailer home, and not in Florida, but my entire house is FlowGuard CPVC for water supply (as with most houses around here).

 

[Squeak]

Do you have enough room to get lengths of PVC pipe up there? If so, you could run the PEX inside that. I see what looks like a nail poking through the sheetrock. PVC would give it some protection.

I do, and that is a great idea. Run some 1.5" PVC as a shield. That would be very easy to do, and make it easier to then run the PEX in there.

Thank you!

 

[Reach4]

Not CVPC. That's for trailer homes and, evidently, most of Florida. No offense.

Current codes do not allow PVC for pressurized water indoors.

 

[Cacher_Chick]

CPVC is approved and fine for potable use anywhere in the U.S.
PVC is not approved for potable water suppy lines indoors.

Personally, I would fish 2 sticks of copper through there and hang them properly, but I have a preference for copper.

 

[Worksmarternotharder]

I would highly recommend CPVC for three reasons:

1. Without the ability to properly anchor PEX, it will flop around in the wall causing noise issues and risking hitting a nail; because CPVC is rigid, it wont move around as much

2. PEX is generally not allowed in plenum spaces because it is highly flammable and can spread a fire in an air chase. Technically that code only applies to commercial buildings, but I wouldn't risk it in my home. CPVC is non-combustible and usually allowed in plenums in my area

3. If you look at the PEX installation guides, there are all sorts of warnings about how to use them in recirc lines, I've heard that PEX can fail in a recirc if there is enough chlorine in the city water.

 

[Squeak]

I would highly recommend CPVC for three reasons:

1. Without the ability to properly anchor PEX, it will flop around in the wall causing noise issues and risking hitting a nail; because CPVC is rigid, it wont move around as much

Agree on the flopping around. I was able to get a 2" PVC pipe in that space last night (and it is pretty well fixed in there now), and figured between that, and wrapping the PEX in foam insulation, it should be pretty rigid now.

2. PEX is generally not allowed in plenum spaces because it is highly flammable and can spread a fire in an air chase. Technically that code only applies to commercial buildings, but I wouldn't risk it in my home. CPVC is non-combustible and usually allowed in plenums in my area

I should be clearer. This is not a true plenum space used for air movement (hot or return). I just called it that to better explain it -- in reality it is just dead space in a soffit created to box in the mechanicals in the basement when finished.

3. If you look at the PEX installation guides, there are all sorts of warnings about how to use them in recirc lines, I've heard that PEX can fail in a recirc if there is enough chlorine in the city water.

Do you have any references for that? SharkBites PEX literature doesn't mention it at all, and Apollo's says it is ok:

"PEX tubing is for use in hot and cold potable water distribution systems as well as hydronic radiant heating systems. PEX tubing can also be used in “continuously recirculating” plumbing systems up to 140°F while maintaining chlorine resistance."

http://www.apolloflow.com/_products/docs/IM_PEX.pdf

 

[hj]

If it were REALLY a "plenum" you would have have been permitted to run ANY plastic through it, but fortunately, it is a chase and you can do it. There should not be anything which would cause the line to "flop" around.

 

[Squeak]

Thanks for the advice everyone. I am assuming that 1/2" PEX would fine for this. Final question: Should it red or blue -- I am assuming red due to it being part of that hot water loop, but didn't know if there was different guideline for the back-end side of a recirc loop.

 

[Cacher_Chick]

The PEX colors serve no specific requirement. It would be perfectly acceptable to use red, blue, or the standard opaque. Some use blue for cold and red for hot, but this is only because the option is there.

 

[hj]

quote; Some use blue for cold and red for hot, but this is only because the option is there.

And also sometimes because the installers cannot remember which line is hot or cold unless the are colored.

 

[Jadnashua]

Red/blue/clear, doesn't matter. Also note, verify the minimum distance from the WH where you can install plastic pipe. In most cases, that's about 2' (maybe 18"). IOW, you generally can't connect plastic pipe directly to the WH.

CPVC will burn, but it is fire retardant. It produces a carbonaceous crust, and releases hydrochloric acid. The crust tends to block the rest from oxygen, thus inhibits further burning. But, if the fire is hot enough...

 

[Squeak]

Just to close the loop on this:

- Had a site survey with my plumber this week and we discussed final plans for the install of the tankless. We talked about the recirc line, and he thought my plan was good one.

- Coupled a pair of 10' 2" white PVC pipe with a flexible rubber junction, fed it into the chase without any issues
- Bought a 100' spool of Sharkbite PEX (red), insulated about 20' of it with foam wrap, and was able to fish it through the PVC very easily.

Now I have 6' of slack at the connection with the water by the sink (plumber said he might just drill right up into the kitchen cabinet and make the connection there), and a spool in my mechanical room waiting for the connection when he installs the heater next week.

Thanks again for all of the advice.