The Jones-Stephens standard two-hole
schedule 40 PVC bath waste kit schematic shows a height for the
elbow that fits under the tub drain of 3 1/8 inches. How
much of that is below the tub?

I took that 3 1/8, added the measurements for a sanitary tee and
p-trap from the Charlotte Pipe catalogue, drew a schematic, get
7 5/8 inches - and that's with the trap flush with the tee,
nothing allowed for the connecting pipe. I have 6 1/2 below the
top of the floor. I'm considering a tub with a drain height of
1/2, which would leave me 5/8 short. I've also considered a
tub with a drain height of 1 3/8, which would give me an extra
3/4. The tub's already on a pedestal. I could lift it a bit
more.



Edited 1 times.

They make street sanitary tees, if this will help with alignment.

Does it? The 1 1/2 san tee measures 1 3/4
+ 11/16, 2 7/16. The street san tee measures
2 1/2. If I can connect the trap to the
san tee with a 1 3/8 piece of pipe, thus
flush, it's 1/16 shorter.

I really want to know how much space I need.

These are dimensions for Charlotte Pipe fittings in 1 1/2" PVC. The overall length of the street tee is 1/8" longer, but 5/8" of that length is inserted into the next fitting, so it's installed length is 1/2" shorter. Are you referring to the tee that picks up the overflow and tub drain?

Finished floor to bottom of joists only 6 1/2”
What size are the floor joists

Have you looked at "above floor drain" bathtubs?

The only length that matters in this case is
the length from the middle of the horizontal
arm to the bottom of the vertical arm.
I just checked my catalogue again: that's
2 1/2 inches for the street, 1 9/16 + 11/16 =
2 1/4 for the regular. Because the trap arm
goes 11/16 up the street, that places its top
at 1 13/16, so that would seem to get me an
extra 7/16. I miscalculated.

Yes, it's the tee that connects the drain and
overflow to the trap.

6 inches

Yes. They give me an additional 3 inches and
cost a lot more because they're specialty
products.
My bathroom is plumbed above the floor. The
old tub was a custom-made product that one
can't buy.
To replace it I had to build a pedestal.
I made a frame of 2x6s and an extra stringer
that support a piece of 3/4 inch OSB floor
sheathing. Because this made it about 1 1/2
higher than the old tub I thought I was in the
clear. Now that I've measured it closely to
make sure I'm not so sure anymore. The old
one drained sluggishly, even after I snaked it
I don't think it had the right slope.
Rather than use an AFR tub I could raise pedestal
with some 1x boards.

are you saying even the p-trap needs to stay within the 2X6 vertical space (actually 5.5" of your pedestal? No room to "sink" the U-bend into?

I could be wrong, but the sanitary tee that connects the vertical overflow and the horizontal tub drain is usually a tubular plastic tee, so that should be smaller then a SCH40 fitting. If the trap is accessible from your pedestal, I wonder if you can use a tubular p-trap and switch to SCH40 until the outlet of the trap, that may save you more fractional inches just tubular is smaller and thinner. I always use SCH40 traps for tub/shower but that is because I have slab homes and there is no access to the trap without breaking concrete later on.

It is actually 6 1/2 inches because I glued
a strip of PVC lattice to the bottom of the
2×6s and put a layer of 3/4 OSB floor
sheathing on top.

When installed the plumbing won't be
accessible so I don't want to use tubular.
I don't even think it would be allowed.

Even installing it is tricky because I have
only a small hole in the side of the
outer-most 2×6. I think I'll have to use
a piece of rope to hold to the horizontal
arm of the trap when welding it. Maybe I'll
pull the whole thing out then slide it back in.

To determine how much of the 3 1/8-inch height of the elbow fits below the tub drain, you need to subtract the measurements for the sanitary tee and p-trap.

If your calculations based on the Charlotte Pipe catalogue show a total height of 7 5/8 inches, that would be the combined height of the elbow, sanitary tee, and p-trap. However, this measurement does not account for the connecting pipe.

Considering you have 6 1/2 inches of space below the top of the floor, you would be 5/8 inches short if you use a tub with a drain height of 1/2 inch. If you opt for a tub with a drain height of 1 3/8 inches, you would have an additional 3/4 inch of clearance. However, this would still leave you 5/8 inches short. If raising the tub a bit more on the pedestal is an option, you may consider doing so to accommodate the required clearance.

--

Caliber Plumbing, LLC
Hollywood, FL

You misunderstood. I am not asking about the
whole waste kit, just the elbow that attaches
to the drain hole in the tub. The Jones-Stephens
catalogue gives it a measure of 3 1/8, from
top to bottom. Some of that is above the
bottom of the tub. After thinking about it,
I think it doesn't matter. 1 1/2 PVC pipe has an
OD of 1 7/8 and I want the distance from the
bottom of the tub to the middle of the horizontal
arm of the elbow, so I can just subtract 15/16
from 3 1/8

Thanks