Big plumbing and drain issue

[deprived]

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.

[awol50]

Your fix sounds like the only solution short of raising the bath tub or lowering the grey water tank and redoing the drains. Just remember your bathtub will become your grey water tank overflow as it fills to the top so you will have to drain it before it completely fills. Not much of a problem though considering the alternatives.

[db7512]

At least your tub will hold more grey water before spilling out on the floor. I am trying to give you a positive thought. I would not try to redo the tub.The new plumbing line sounds like it should work.

[Larry]

The only proper way to fix it is to raise the tub, otherwise the top of the gray tank will always be backing up in the tub. Only other option is to lower the gray tank or install a shorter gray tank so you can keep the original plumbing set up.

[ThePowells]

Your plan to add the second line will work, but the level at which the gray will back up into the bathtub will be lower so you are going to lose a little gray capacity.

[DrPhil]

Has a tight fitting tub stopper been considered. If that works (could be used perm.), then what about a strategically placed check valve? Also wondering why the tub just doesn’t drain after slightly filling, so have your vent pipes been checked to make sure they are open and clear to roof?

[DENSHER]

One other option. Install a Back Flow/One Way Check Valve between tub drain and where sink tee's into line.

[charliez]

Plan C Worth a try. Cut into the new tub drain pipe and add am upside down U inline before it meets back up with the existing drain pipe. Maybe that will force the sink drain towards the gray tank. Not sure how the tub will drain tho. Or plan D. Put a plug in the tub when not using it. I'd probably try plan D first.

[bldrbob]

Instead of tapping on the side I would run a new drain into the top of the tank. According to the drawing the drain goes under the floor so the new tub drain should fit and not affect the capacity of the tank.

[Campasaurus]

Would a backflow valve for a sump pump be a low cost fix?

[Bob_C]

I hard plumbed my kitchen dump valve, is under slide, to the front grey/black tank dump connection......using the right glue is the trick......and as a safety, apply a little silicone around the glued areas...

[deprived]

I ended up doing, as some suggested, running a new line to the top of the tank. Since the photos were taken I reinforced the connection with marine epoxy which sticks nicely to both the PVC pipe and ABS tank.

It works great.

Thanks for the replies!

[Ray,IN]

Originally Posted by DENSHER

One other option. Install a Back Flow/One Way Check Valve between tub drain and where sink tee's into line.

I agree,
This is the simplest and most cost effective solution. Hepvo valve

[eddndee]

If it is possible for a backflow event to occur I would definitely include some sort ofbackflow preventer.