Okay. I messed up - I admit that.I tore out the old shower in our 2008 Tiffin and replaced it with a bathtub. It was a huge effort that took several weeks to complete.And now for the bad news.The new tub fills up with drain water from the bathroom sink because the new tub sits about three inches lower than the old shower. That little bit of difference is just enough to allow the sink to drain partially into the tub which fills up with about one or two inches of water. I have two choices to fix this, as far as I can see. 1: rip out the new tub and rebuild the entire thing. Let’s call that plan “B”. Or plan “Z”. I really, really don't want to do that.2: make the tub drain pipe a bit lower and plumb a new second line to the grey tank. This new line from the tun drain will drop down a few inches beneath the floor and enter the grey tank from the side rather than the top. This will diminish my grey tank capacity a bit but it’s still a hell of a lot easier and cheaper than undoing a month’s worth of work.There are some issues with cutting a new fitting into the grey tank but I’ve see a few methods using ABS fittings and solvent-cements that seem to work well. That part is tricky but surmountable. Otherwise it is a fairly straightforward job.I’m not saying this is a perfect plan (or even a good one) but I wanted to put it out there to see what you all might have to say in terms of other ideas or improvements to the plan.I found a picture of the old drain, and I can see that it sits about three inches higher than my new configuration.NOTE: my diagrams are not all that accurate but I think they illustrate my situation.

where do you camp, how do you drivealways somewhere with hookups, always dump before you move ?i think i would remove the tub and raise it, aka do it rightyou run the risk with your fix, of getting more than just the basin waterbacking up in your tubnear full hard corners, could get some really bad grey water in the tubsure the 'water might drain' on the next opposite turnbut kind of scum would it leave behind in the tub ?

Can't you just leave the tub drain closed when not using it. The water can't back up into the tub then unless your overflow drain is also an issue.

Halmfamily wrote:Can't you just leave the tub drain closed when not using it. The water can't back up into the tub then unless your overflow drain is also an issue.That would work until he went to use the tub. Once he opened the tu drain the grey water would rush/flow in.You could consider a check valve in the drain line.

Where the drain line enters the tank, install a sani tary tee vertically at the tank, have the sink plumbed to go in the top of the tee andd the tub into the side.https://www.nachi.org/gallery/?level=picture&id=2650

Other than the sink draining into the tub, are there any other issues (does the tub drain if the sink is not in use)? If it empties properly with your new setup and the only problem is sink water draining into the tub, why couldn't you give each a dedicated drain line into the grey tank as in your "fix" above, but rather than plumb into the side have the new line go into the top like the original?

Bathtub rebuild drain issues!! | Good Sam Community

4x4van
Explorer III
May 22, 2018
Am I correct in assuming (from your diagrams) that the bottom of the tub is now lower than the drain pipe (that is running along the floor)? If so, then the tub will never drain correctly, even without the sink being in the picture.

If it were me, I would redo it right and raise the tub so that the bottom of the tub is above the level of the drain pipe. Class C's typically don't have an overabundance of grey/black capacity anyway, so doing anything that would reduce that would be a no-go in my book. But if that's OK for you and your use (full hookups rather than boondocking?), then your idea of a separate drain into the side of the grey tank would work, IF you can be sure of getting a good seal at the new entrance into the grey tank.
wolfe10
Explorer
May 22, 2018
I would look into either a ball valve for the shower drain (closed except when showering) or a check valve/one way valve for it.

A plumbing supply house would be my first stop for ideas.
SWFL_FlyFisher
Explorer
May 22, 2018
Other than the sink draining into the tub, are there any other issues (does the tub drain if the sink is not in use)? If it empties properly with your new setup and the only problem is sink water draining into the tub, why couldn't you give each a dedicated drain line into the grey tank as in your "fix" above, but rather than plumb into the side have the new line go into the top like the original?
eHoefler
Explorer II
May 22, 2018
Where the drain line enters the tank, install a sani tary tee vertically at the tank, have the sink plumbed to go in the top of the tee andd the tub into the side.

https://www.nachi.org/gallery/?level=picture&id=2650
Lantley
Nomad
May 22, 2018
Halmfamily wrote:
Can't you just leave the tub drain closed when not using it. The water can't back up into the tub then unless your overflow drain is also an issue.

That would work until he went to use the tub. Once he opened the tu drain the grey water would rush/flow in.
You could consider a check valve in the drain line.
Halmfamily
Explorer
May 22, 2018
Can't you just leave the tub drain closed when not using it. The water can't back up into the tub then unless your overflow drain is also an issue.
MrWizard
Moderator
May 22, 2018
where do you camp, how do you drive
always somewhere with hookups, always dump before you move ?

i think i would remove the tub and raise it, aka do it right

you run the risk with your fix, of getting more than just the basin water
backing up in your tub
near full hard corners, could get some really bad grey water in the tub
sure the 'water might drain' on the next opposite turn
but kind of scum would it leave behind in the tub ?

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