Cross Floor Plumbing

[o1marc]

My tanks are on the drivers side with the shower, but I want my kitchen sink on the passenger side. Can a 1-1/2" pvc fit over the frame rail below the floor ribs to the opposite side?

[Jolly Roger bus 223]

On mine it can.
You will have to cut a whole big enough for the long sweep elbow to fit up tight to the floor on that side and let the pipe rest on the second frame rail to have minimum grade if the bus is setting perfectly level.
For a single sink you can change to 1-1/4" pipe which will give you a little more wiggle room for grade.
Or change copper drain and get a little more.
PVC pipe is measured the same as sch.40 steel with 1-1/2" being the ID but the actual OD is 1-5/8"
For copper the size is the OD.
If you have to go the copper route it will be more expensive of course.
They do make copper drain line fittings and pipe.
Have to wrap it with tape or I use old water hose tubing at rub points
And I would do on any pipe near anything harder than it is.
I actually sleeved mine and anchored the sleeves.
I opted out of crossing the frame rails cause I know I won't be parked level all the time and could see it being an drainage issue.
So I changed the layout for all the grey on the same side and ran my sink drain in the wall.
But I furred all of my walls out with sheetmetal studs 1-1/2" from the ribs to accommodate that stuff.
The thoughts I just posted were based off of me pondering and measuring how to do the cross rail thing myself and my decision's are based off of my now 25 years of commercial plumbing and commercial HVAC piping experience as an installer and having to figure out other companies messes left behind.
Hope this helps you Marc

[somewhereinusa]

I actually have two crossings. There is a grey tank on both sides connected together at the bottom. Shower is on the left side just above the left grey tank so the shower drain goes to the right side with a hepvo trap. I cut the floor installed the drain then put then put a patch over the hole. The toilet is also on the left and it's vent crosses to the vent stack on the left. Both sinks are on the right.
The only thing I would have done different is to put two drains in opposite front and rear corners of the shower. One of the places I go often it's just not possible to get completely level.

[o1marc]

Jolly Roger, I like the idea of pulling the connection tight to the floor for slope. Though I can't imagine the slope would be much. I had also planned on having the cross line angle from the drain towards the rear into the tank, so any forward motion will empty the line.

[TheArgobus]

I was going to do something similar. My fresh tank is on the right side along with the water pump, and my grey tank is on the left side.


The sink for sure had to go on the left, and I only had space for one tank per side. So I had to decide which side would be fresh and grey.



I opted to make the right side (opposite of the sink) fresh, and just plumb the pressurized PEX tube across to the left. Originally, I was going to go under the bus like what you're saying, but then I decided to just plumb it through the rigid insulation of the floor.


I figured I'd rather have the pressurized water go across as opposed to draining, because like what others are saying, the slope can getcha, and I didn't want the potential for any blockage halfway across. So the sink just drains straight down into the grey tank.


I HIGHLY recommend the Hepvo fitting, I think PNW Steve originally clued me in to that great contraption. It saves a lot of space and just make things easier.

[o1marc]

I did opt for the Hepvo trap over a "P" trap. It arrived in today's mail. I would prefer to do the crossover inside and not under if possible. I have 1-1/2" rigid on the floor that it could fit in. But I also have Pex running fore and aft for floor heating that I will have to deal with.