Clearance needed between shower drain bottom and waste water tank?

[musigenesis]

I'm going to be building the tray for my tub which will be projecting below the floor a few inches, and I want to make sure I have sufficient clearance for everything. Right now, I'm planning on having the bottom of this tray be 8" below the level of the factory floor.

I'm planning on having a waste water tank like this one: https://www.amazon.com/Class-Customs-Gallon-Holding-WT-4000/dp/B07NLLQDC1/ suspended underneath the bottom of the tub tray. This tank is 9" high, and the skirt on the side of my bus extends about 20" below the level of the factory floor, so if the bottom of the holding tank is flush with the bottom of the skirt, there will be a 3" gap between the tub tray and the tank.

I was thinking I could just have a pipe connecting the tub drain with an opening on top of the waste water tank, but I think that might be an odor problem. What kind of attachment should I have here, and what kind of clearance does it require?

 

[PNW_Steve]

You need a P-trap at the shower drain to keep tank odor from entering your living space.

There is an alternative to the P-trap that I have not tried. Perhaps someone who has experience with them will chime in.

 

[Danjo-SKO]

P Trap

Figure 8 inches. You might be able to do it in 6 but it depends on how much maintenance you expect to need. I’d get one with a Union if it will be accessible enough. Now if it can be offset to the tank you could do it with as little as 3”

 

[Danjo-SKO]

P Trap

Figure 8 inches. You might be able to do it in 6 but it depends on how much maintenance you expect to need. I’d get one with a Union if it will be accessible enough. Now if it can be offset to the tank you could do it with as little as 3”

 

[o1marc]

No room for a P trap. What you need is a Hepvo valve. It mounts horizontally and has a rubber tube that closes at one end once the fluid has drained, keeping the smell contained. In our application P traps can dry up, negating their benefit.

 

[ol trunt]

Ditto on the P trap.You made me curious so I went out and measured mine--8". I used a 7 gal water carboy with a lift pump up to my grey water tank which is under the stove inside the bus. All the grey water eventually flows into the black tank which looks a lot like what you are thinking about using.
Jack

.

 

[PNW_Steve]

No room for a P trap. What you need is a Hepvo valve. It mounts horizontally and has a rubber tube that closes at one end once the fluid has drained, keeping the smell contained. In our application P traps can dry up, negating their benefit.

That is the Gizmo that I was thinking of. Have you tried one out yet?

I am tempted to try one but I have concerns about debris keeping it from sealing properly.

I have had P traps in all of my RV's and have never had trouble with them drying up. I do have trouble with the P trap drying up in my spare bath at home.

 

[o1marc]

That is the Gizmo that I was thinking of. Have you tried one out yet?

I am tempted to try one but I have concerns about debris keeping it from sealing properly.

I have had P traps in all of my RV's and have never had trouble with them drying up. I do have trouble with the P trap drying up in my spare bath at home.

I have one on my bus, though it isn't in use yet. I have used several in residential construction. They are good for sinks and showers. What kind of debris are you referring to? I plan on screens in my drains to keep solids from getting into the tank.

 

[musigenesis]

No room for a P trap. What you need is a Hepvo valve. It mounts horizontally and has a rubber tube that closes at one end once the fluid has drained, keeping the smell contained. In our application P traps can dry up, negating their benefit.

This looks like exactly what I need, thanks. My bus is probably going to sit idle for long stretches, so a dried-out p-trap seems like a definite possibility.

 

[JDOnTheGo]

As mentioned, a p-trap is what we commonly use here in the USA. I spent a bunch of time in Europe recently and noticed their "bottle traps" which are their common variation of a p-trap. This is an example that might be a solution to clearance issues. They also make a low profile variant, I couldn't find exactly what I saw in Europe but this is fairly close. I think either would work fine on this side of the planet.

 

[musigenesis]

Ditto on the P trap.You made me curious so I went out and measured mine--8".

You also have a shower/tub that projects below the floor? I really need to go through your whole build thread.

I'm going to go ahead and make my tray 8" deep. This will leave me with a 6" lip to step over to get into the tub and 6'6" of headroom in the shower, same as in the center of my lowered floor.

Now I have to work out how to run the drain from my kitchen sink (which will be right next to the tub) into this.

 

[PNW_Steve]

I have one on my bus, though it isn't in use yet. I have used several in residential construction. They are good for sinks and showers. What kind of debris are you referring to? I plan on screens in my drains to keep solids from getting into the tank.

Hair & larger particles . I sometimes get in the shower in a very grimy condition.

I am most concerned about hair.

 

[musigenesis]

As mentioned, a p-trap is what we commonly use here in the USA. I spent a bunch of time in Europe recently and noticed their "bottle traps" which are their common variation of a p-trap. This is an example that might be a solution to clearance issues. They also make a low profile variant, I couldn't find exactly what I saw in Europe but this is fairly close. I think either would work fine on this side of the planet.

That Wirquin low-profile one looks very interesting. This would let me mount the waste tank higher, with something like a 1" gap instead of a 3" gap, since the trap would be flush with the bottom of the 2" of insulation I'll have underneath the tub (I was thinking I'd have a 2" drain extender going through the insulation, and then my p-trap would start from there). I'd have to alter my tray a bit to accommodate it, though (which is fine I haven't started on it yet).

 

[musigenesis]

Hair & larger particles . I sometimes get in the shower in a very grimy condition.

I am most concerned about hair.

Hmm, nobody's seen Sasquatch since camera phones became a thing - is that because he's now living in a school bus? :biggrin:

 

[o1marc]

Hair & larger particles . I sometimes get in the shower in a very grimy condition.

I am most concerned about hair.

Get you a drain screen, that will prevent hair from clumping before it hits the drain pipes and valve.

 

[kidharris]

I'm going to be building the tray for my tub which will be projecting below the floor a few inches, and I want to make sure I have sufficient clearance for everything. Right now, I'm planning on having the bottom of this tray be 8" below the level of the factory floor.

I'm planning on having a waste water tank like this one: https://www.amazon.com/Class-Customs-Gallon-Holding-WT-4000/dp/B07NLLQDC1/ suspended underneath the bottom of the tub tray. This tank is 9" high, and the skirt on the side of my bus extends about 20" below the level of the factory floor, so if the bottom of the holding tank is flush with the bottom of the skirt, there will be a 3" gap between the tub tray and the tank.

I was thinking I could just have a pipe connecting the tub drain with an opening on top of the waste water tank, but I think that might be an odor problem. What kind of attachment should I have here, and what kind of clearance does it require?

This is a grew water application so any of the following should work. The pump is more flexible design wise.



If it is going into a grey water tank there should be no smell, so no p trap necessary (if for some reason your grey water tank started smelling a little bleach will take care of it).


I would set the bottom of the shower the height that I wanted and use a pump and transfer the water to wherever I wanted it to go. Again no p trap needed. You could even use a y and a hose bib and a garden hose and water a tree if circumstances allowed.



You could also use a big ball valve (1.25" - 2") in the drain line if draining straight into a tank (elbow first if needed). Use linkage with swivels like you use on a socket set if needed for alignment to turn the valve on and off. This is how a lot of commercial stainless steel kitchen sinks are set up in Vegas. some are set up to use a foot operated spring loaded paddle lever to operate the valve. Again no p trap needed, just shut the valve to stop smells if hooked up to a black water tank/sewer.


In all cases a hair strainer on the drain would be helpful, especially for a pump setup.

 

[kidharris]

You also have a shower/tub that projects below the floor? I really need to go through your whole build thread.

I'm going to go ahead and make my tray 8" deep. This will leave me with a 6" lip to step over to get into the tub and 6'6" of headroom in the shower, same as in the center of my lowered floor.

Now I have to work out how to run the drain from my kitchen sink (which will be right next to the tub) into this.

I think Ol Trunt has a set up with a macerator pump and hose that would take care of kitchen sink garbage. Ask him about it. Probably expensive though.

 

[musigenesis]

This is a grew water application so any of the following should work. The pump is more flexible design wise.

If it is going into a grey water tank there should be no smell, so no p trap necessary (if for some reason your grey water tank started smelling a little bleach will take care of it).

I would set the bottom of the shower the height that I wanted and use a pump and transfer the water to wherever I wanted it to go. Again no p trap needed. You could even use a y and a hose bib and a garden hose and water a tree if circumstances allowed.

You could also use a big ball valve (1.25" - 2") in the drain line if draining straight into a tank (elbow first if needed). Use linkage with swivels like you use on a socket set if needed for alignment to turn the valve on and off. This is how a lot of commercial stainless steel kitchen sinks are set up in Vegas. some are set up to use a foot operated spring loaded paddle lever to operate the valve. Again no p trap needed, just shut the valve to stop smells if hooked up to a black water tank/sewer.

In all cases a hair strainer on the drain would be helpful, especially for a pump setup.

Hmm, some interesting ideas, thanks. Maybe I indeed don't need anything special at all since this is just gray. The ball valve might be good, too.

I don't think I want to deal with a pump for this.

 

[DrDanger]

My solution

I posted a short update here, but I'll go into more detail here for those in the "sunken shower club".


First, I only lowered my floor about 4in which, in retrospect, is not enough for what I wanted. I didn't account for the height I would lose due to the shower pan (because I had no idea how I was even going to do that at the time).

Also, because I didn't plan it out that well, I didn't make it a standard size so I couldn't use a pre-made shower pan. Therefore I made my own shower pan with concrete like you would in a house. I think in the end I have about a 2in step down (maybe 3in in the center where the drain is). Anyway, the question in this thread is how do you drain your sunken shower, so here is my solution.

The tank is from an old basement sump pump. It had the threaded inlet at the top so I put a 2in P-trap on the shower, but had to neck it down to the 1 1/2in inlet. I had a several uniseals left over so I just put the drain on the side (should only leave 1/2in of water in the bottom). In retrospect I probably could have bought a bulkhead fitting to go straight on the bottom of the tank but I was in a hurry. Then I plumbed it into the drain for the gray tank like so...

Theoretically the shower won't back up until the gray tank is 80% full, but I am not sure how fast it will actually drain. I finished the tile and whatnot yesterday so my first test was today. It was draining slowly and backing up into the shower until I went out and opened the drain for the gray tank. I don't know if this means the gray tank was too full, or if I need to put a vent on the shower catch tank itself. More testing to follow.
If this system doesn't work, I have a macerator pump that I will use to drain the shower tank and pump it into the top of the gray tank via a clean-out inside.


The T fitting pointing away from the camera is a clean-out that will allow me to plumb in a drain from the other side of the bus if I ever get around to putting a sink in the bathroom or making a urine diverter for the composting toilet.

 

[o1marc]

You might consider a HepVo valve in place of the "P" Trap. Driving will slosh alot of the water out and heat will evaporate the rest faster than you think, and then stink. HepVo gives you a few more inches of clearance to drop the pan another 3-4".