help in design of new bathroom

[ridgemount]

I am in need of a little help. I am currently renovating a bedroom to turn it into a new bathroom. I have attached a picture to show my layout. The help i need is will it work the way i desgned it. Some people say i need to tie the bath, shower and sink drain after the toilet and not before it.
Thanks for any help given.

[LazyPup]

Technically a watercloset (Toilet) must always be on the end of a line. You are correct in your proposed placement of the watercloset because you have a Wye off the main line with the closet flange on the end of the Wye branch, even as short as it may be.

You did not mention where you live nor is it posted on your profile so we cannot be sure which code your under.

If you are under the IRC (International Residential Code) an 1-1/2" line to the tub is fine but if you are under the UPC (Uniform Plumbing Code) the tub trap may be 1-1/2" but the drain line must be 2". The reason is that a tub is rated at 2DFU's while under the UPC an 1-1/2" drain line is limited to a maximum of 1 DFU while a 2" horizontal line is rated for a maximum of 8 DFU's.

NOTE; DFU = Drainage Fixture Units, the basic unit of measure for determining all DWV line sizes.

Given that you will have an auxiliary vent on the upstream end at the lavatory both the tub and shower waste arms will wet vent to the 2" horizontal from the watercloset location to the lavatory location.

in your illustration you show the tub drain line beginning at the tub drain opening but that is not correct. The tub is connected by means of a Waste & overflow kit and the tub trap inlet would actually be directly below the overflow riser under the tub apron as I have illustrated in the solution drawing. The trap would then extend in the direction of flow for about 6" from the trap inlet to the trap weir. (The trap weir is the physical point on the discharge side of the trap U section where the water would spill out of the u and into the horizontal drain line.).The length of the tub fixture arm would begin at the tub trap weir and continue to the point where the tub line connects to the 2" horizontal main.

Under the IRC an 1-1/2" fixture arm may run 6' from the trap weir to vent opening which in this case would be the 2" main line.

Under the UPC the line from the trap must be a 2" line and may not exceed 5' from the trap weir to the 2" main.

Under both the IRC & UPC the shower line must be 2".

There is a problem with your proposed offset for the vent line at the lavatory location. We may not run a vent line horizontally until the vent line reaches an elevation at least 6" higher than the flood level rim of the highest fixture served by that vent. Typically we would run the drain line directly to a point below the lavatory waste arm location, then run the line straight up with a Tee at the lavatory fixture arm height and continue the vent line directly up from that point, however considering that you desire an offset I must then assume that you either have a window there or you intend to install a recessed medicine cabinet. If that is the case, there is a simple solution as i have illustrated in my solution drawing.

At the point where the shower drain connects to the horizontal 2" main you can install a Wye & 1/8th bend with the shower drain connecting to the side inlet of the Wye. On the end of the wye you would then install a female thread adapter and a cleanout plug.

At the point where you propose the vent riser you could continue that line straight down, then horizontally and connect it to the shower drain line with a why & 1/8 bend as illustrated.

At the elevation for the lavatory drain you can install a Tee on the vent riser, then extend a horizontal line over to the lavatory drain location and stub it out to the lav trap.

In this manner all the line from the Tee on the riser to the 2" main drain would be classified as a "Combined waste & Vent", and the actual length of the shwer fixture arm would then be from the Wye on the shower line to the shower trap weir, which would put you well within limits for both codes.

[ridgemount]

Thank-you for your fast response. I am going to pick up all the materials and get the job done. I will let you know how I make out on it.

Thank-you once again.