Flexible DWV

[bobbyt]

Hi,

I have a kitchen remodel where I have to move the sink over 6'. The only way to get the 2" drain line over to where it has to go is thorough 4 2x10 joists.

I can put short segments of pipe in with couplings but I had the idea to use 2" flexible schedule 40. Is this legal? I can ensure that the pipe is straight and graded appropriately.

Thanks,
Bob

 

[Reach4]

I can put short segments of pipe in with couplings but I had the idea to use 2" flexible schedule 40. Is this legal?

No.

 

[Sponsor]

 

[bobbyt]

No.

That's unfortunate. It would be a much smoother flow than for couplings.

Is the concern that the pipe would not be straight enough?

 

[Reach4]

That's unfortunate. It would be a much smoother flow than for couplings.

Is the concern that the pipe would not be straight enough?

You are asking me the logic as to why SpaFlex is not listed in the list of approved materials for drain stuff in the codes. I don't know that. It may be, as you suspect, that it would tend to sag between supports.

I can tell you that if you want to minimize the hole size for 2 inch pipe through your joists, you could use copper pipe, and then solder the couplings into place.

 

[wwhitney]

I have a kitchen remodel where I have to move the sink over 6'. The only way to get the 2" drain line over to where it has to go is thorough 4 2x10 joists.

Hopefully you can do it with just 2 couplings. You can drill up to a 3" hole in a 2x10, minimum 2" clear from the top an bottom of the joist. If you make the lowest hole you need the full 3", with the extra diameter towards the bottom of the joist, you can probably fit a piece of pipe that is at least 1.7 joist bays in length through that hole. 3 of those pieces (2 couplings) would be enough to cross 5 joist bays.

Cheers, Wayne

 

[Reach4]

Four glued couplings would not bother me.

Hopefully you can do it with just 2 couplings. You can drill up to a 3" hole in a 2x10, minimum 2" clear from the top an bottom of the joist. If you make the lowest hole you need the full 3", with the extra diameter towards the bottom of the joist, you can probably fit a piece of pipe that is at least 1.7 joist bays in length through that hole. 3 of those pieces (2 couplings) would be enough to cross 5 joist bays.

Are you suggesting one 3 inch hole, or two?

 

[Jadnashua]

It’s not uncommon for a kitchen sink to be near a window, and that often will mean the outside wall and the end of a joist. There are requirements about how close to the end of a joist that you can drill holes, so it may not be possible to do what you want without dropping the drain line below them, so drilling isn’t an issue. You MIGHT be able to run the drain in the wall, depending on the depth of the studs, then down. Worst case, you run it horizontally at the back, inside of the cabinets before you can run it down, or under them. They all mostly have a toe kick so the bottom of the cabinet has some space there.

 

[wwhitney]

Are you suggesting one 3 inch hole, or two?

Just one. For smaller pipe (which is a little bendy, like 1" PVC), two oversized holes might allow you to do the whole thing without couplings. The second oversized hole would be biased upward rather than downward.

But one 3" hole, biased downward, should let you start with a segment that is a bit less that two joist spacings long at a diagonal through the hole, and hopefully the trailing end clears the rear joist before the leading end hits the subfloor. Then once you've got the segment in those two bays, you can slide it through your normal size holes, and repeat.

Cheers, Wayne

 

[WorthFlorida]

I could not find the max number of holes allowed for the outer 1/3 of a floor joist but up to a 3" is allowed for a 2x10. I found that a general rule a second hole should not be closer than the diameter of the holes. A structural engineer stated, on another forum, that the holes act like an open trust and the strength is not compromised. As long as the inspector agrees(?). One 3" hole in each joist may be enough wiggle room to flex a SCH40 PVC 2" pipe. As WWhitney stated, the first hole angle it to get a start. Note, you can drill holes through joists adjacent to where you need to run the pipe if you needed to get more flex. That is you might be able to flex a 10' pipe with leverage but not a 5' length.

However, jadnashua suggestion to run the pipe under the cabinet along the floor is probably the easiest way to go, just keep a slope

https://joistrepair.com/products/2810hr

 

[bobbyt]

Thanks all fot the good info and suggestions. I think that if I also notch the joist ahead of the one with the first 3" hole, it would give me more angular advantage.

 

[Tuttles Revenge]

You can install 30" sections of pipe between joists.. Send the first piece all the way down then the next and so forth. Best is to run a string line or laser and measure each of your holes from that line rather than measuring from the top of each joist since they could each be out of plane by a a little bit each.

When we open up old homes with lead pipe... where its not supported, its sagged. Plastic would do the same with hot water running through it constantly. To keep lead pipe from sagging they would lay a board between joists or studs to support it in its entirety.

 

[bobbyt]

Tuttles, your explanation for why it's not allowed and your suggestions on how to run the line make a lot of sense.

Thanks!