Shower/Tub drain in basement question

[CheezHed]

My house is 3 years old and was rough plumbed for a bath in the basement. I'm framing it up now and I'm wondering about venting and drain location. As you can see in the photo, where the wall hiding the vent is going to be (the darker pressure treated one), it's only 3.25" to the center of the drain where the tub/shower is going to go.

All the shower bases I've looked at need anywhere from 7" to 16" to where the drain center is (from the wall). Even if I put in a tub with a drain on the side I think the drain in the concrete is too close to the outer wall.

Would you build up a base to put the shower/tub unit on so you can run a pipe to the drain? I was even thinking about bumping out the wall to allow for whatever base I pick, but I don't want that bump in the adjoining room. Or would you bust up the concrete and move the drain to fit what you need? Maybe if I dig deep enough in the dirt where the drain is coming out and chip away a little concrete I could still get the drain connected running downhill?

Seeing the vent coming out of the concrete, I'm assuming that both the toilet and tub drain are already connected to it?

Thanks for any advice! If the wife doesn't see progress when she gets home tonight I'm in deep doo doo! I'm really leaning towards a shower down there. I don't think a tub would hold the heat too well with cold concrete right underneath it.

[LazyPup]

You must keep in mind that a tub is connected by means of a "waste & overflow kit". Immediately behind the tub overflow the pipe turns straight down to the trap. The actual tub drain is then Tee'd into that line by the tub waste shoe.

While it appears that the drains are well within the prescribed length limits from trap to vent you would encounter another problem if trying to convert this roughin for a shower stall. It appears that the existing drain line is an 1-1/2" pipe, which is the prescribed size for a tub or tub/shower however a shower stall requires a 2" line. Understanding that a waste line may not be decreased in size in the direction of flow, it would then stand that if you wanted to change this roughin to a shower stall it would require breaking out the concrete and changing the 1-1/2" line to a 2" line.

You must also keep in mind that tub waste & overflow kits are made in two styles, slip joints and glue in. Slip joint waste and overflow kits may only be used if there is a minimum of a 12" x 12" service access either from underneath or through an adjacent wall. When the waste and overflow is concealed you must use a glue in type.

Installing a glue in type waste & overflow can be very tricky because it must be completely set up before the tub is dropped in place and there is no opportunity to change any positioning once it is set in place.

In this instance the easiest method would be to install a Trap adapter on the end of the existing drain pipe, then use a slip joint type waste & overflow kit and provide a service access panel through the framing from the adjacent room.

[CheezHed]

Good point!

I just double checked the drain, it's a 2". So I can still go with just a shower, no tub. Does the drain have to be 'directly' beneath the drain opening in the shower base? Or as long as you have room to plumb it downhill to the drain is everything cool?

And do you suspect that the drain has a trap underground? I don't know how I could verify this.

Thanks for the quick response Pup!

[LazyPup]

There should be a P-trap at the point where that vertical stub changes to a horizontal run.

Remove the cap and look down the inside of the vertical stub. You should be able to see the bend where it changes to horizontal. To confirm the presence of a trap slowly pour a couple quarts of water in the pipe. If that bend is just a normal 1/4 bend the water will quickly flow away however if it is a trap you should be able to see the water standing in the trap.

You may want to add some dark colored food coloring to the water to increase the visibility in the pipe.

Also measure the inside diameter of that pipe carefully. If it is a 2" line you would be able to use it for a shower stall.

While it is customary for a shower pan to have the drain centered there is no hard and fast rule that requires it. You could consider making a "Site built" shower pan with the drain opening on the side. The only requirement is that the floor of the shower pan must be pitch at 1/4" per foot but not more thn 1/2" per foot in the direction of the drain and the door threshold and shower pan curb must be a minimum of 2" but not more than 9" higher than the finished elevation of the drain opening.

I would be very hesitant to install an offset from the drain opening to the waste line because that would make snaking the pipe extremely difficult if the need should arise.

If you are under the International Residential Code the minimum rough pan dimension must be 32" x 32". If under the Uniform Plumbing Code the minimum rough pan dimension must be 34" x 34".

If constructing a "Neo Angle" shower the rough pan must be 39" x 39" and the door must be a minimum of 22" wide. The door must swing outwards.