I have to state publically that lazypup rocks! He sent me this very detailed email, accompanied by the drawing below. I wanted to post it for anyone else who might want to learn a thing or two about plumbing and codes. I know I sure did. His advice: On first inspection your bathroom project appeared very simple, but as I began going over the details it soon became apparent that your project has a number of rather unique problems to overcome, so much so in fact that I intend to add this bathroom to my apprenticeship training program. To make matters worse, the Indiana Plumbing Code is based upon the Uniform Plumbing Code (UPC), which is much more restrictive than the International Residential Code (IRC), especially in regards to venting requirements. For the purposes of discussion let us assume your print to have standard map orientation thus the top is north (N), the bottom south (S), the left side west (W) and the right side is east (E). Let us begin with the shower and watercloset drain (Common name "toilet", proper name "watercloset"- abbreviated WC). The shower enclosure is 36" N x S & 48" W x E with the drain opening centered @ 18" north of the south wall. We have a stud wall running N to S between the shower & WC enclosure and the WC is centered against the E wall of the enclosure. This means the closet flange must be 12" W of the finished E wall and centered between the N & s walls at 18". Problem: Both the shower and WC drains are centered at 18" however the flow from each fixture opposes the flow of the opposite fixture but code requires each to connect to the receiving drain line in the direction of flow. To add further complication, the code prohibits installing a Tee on a horizontal line; therefore we cannot join the two lines over the vertical drain riser in the load-bearing wall with a Tee. WE could come forward from the WC to a point over the LB wall, install a 1/4bend to turn 90deg then install a Wye to connect the shower line but; Code prohibits notching the underside of the joists so we must find a solution that fits within one joist bay. We could install a 3x3x2 side inlet 1/4bend under the closet flange but that would place the inlet too high to permit the required pitch on the drain line from the shower. We have one quarter bend under the closet flange, which turns the closet flange line from vertical down to horizontal. We will need a second quarter bend on the horizontal to turn it down to the riser in the load-bearing wall. The riser in the load-bearing wall is approximately 24" from the E wall, however the closet flange must be mounted at the standard 12" offset. We then have 12" horizontal remaining from the closet flange centerline to the vertical riser centerline, but each quarter bend requires a 4.5" fitting allowance for a combined allowance of 9". There is no fitting that would fit in the remaining 3". The solution is to install a 3" quarter bend on the closet flange then a 3x3x2 side inlet quarter bend on the top of the vertical riser. The finished elevation of the side inlet will be determined by the pitch from the shower drain once the trap and drain line is completed, (see attached illustration). The side inlet can be placed on the north or south side of the closet drain line depending upon how the WC fits in the joist bay. Place the side inlet on the side, which gives you the most clearance. Next install the shower drain basket assembly & P-trap. Keep the p-trap as high as possible and angle the tailpiece of the P-trap at 45deg towards the side of the joist bay on the same side as the side inlet on the vertical drain line. Code requires that all PVC pipe must be supported at not more than 48" increments so in this manner you will be able to install a pipe support on the side of the joist bay. You will need a 2" vent so at the point where the shower drain line passes under the stud wall between the shower and WC enclosures install a Wye & 1/8 bend or a combo with the side inlet pointing up. You will then extend a 2" vent line up through that stud wall to the attic space. Once in the attic space you may continue on out through the roof or you may turn it horizontal and connect to the lavatory vent before going through the roof. From the vent location continue running the drain line towards the vertical drain along the joist until you can make a 45deg offset to the side inlet on the drain line. (Do not make a 90deg offset because code requires we install a cleanout at every change of direction greater than 45deg.). At this point we have concluded the shower and WC drain and we can turn to the lavatory drains. LAVATORY DRAIN; Per industry & code standard lavatories (common name bathroom sink) have a 1-1/4" drain opening and tailpiece. Code also states that the P-trap and fixture arm should be the same size as the drain opening however code will allow us to increase the size of a P-trap or drain by a maximum of one nominal trade size. Given that the lavatory fixture arm and lavatory drain is the only line in a residential structure that is permitted to be 1-1/4 most plumbers have opted to fall back on the code exception allowing us to increase to 1-1/2" rather than maintain a separate inventory of 1-1/4" pipe and fittings for this limited use. In fact, this practice has become so common that it is often now difficult to find 1-1/4" pipe and fittings anywhere outside of a dedicated Plumbing Supply house. Previously I stated that the UPC is a bit more restrictive than the IRC. Under the IRC all structures are required to have one main vent which must run undiminished in size from the building main drain through the roof, then all auxiliary vents may be reduced to ½ the diameter of the line they serve providing the vent is no smaller than 1-1/4". Under the UPC we are not required to run a building "main vent" however all vents are required to be sized from a table in the code based upon the number of DFUÂs on the line served and the combined aggregate cross sectional area of all vents must be equal to or greater than the cross sectional area of the main drain. Under the UPC both a 1-1/4" line and a 1-1/2" line are rated for a maximum load of 1DFU however an 1-1/4" vent is rated for a maximum of 1DFU while an 1-1/2" vent is rated for up to 8DFUÂs providing there are no WC served by the vent. (WCÂs require a minimum of a 2" vent) In this case we are planning to vent both lavatories with one vent line so we will need a 1-1/2" vent line. Beginning at a point directly behind the lavatory on the NW corner of your bathroom mark the point where the fixture arm will stub out to the sink trap (16" to 18" above the finished floor). At that point you will install a sanitary tee with a stub-out from the side opening to a trap adapter to connect the trap to the sink. From the top of that tee you will run a 1-1/2" vertical line into the attic space for the vent. From the bottom of that tee you will install a 1-1/2" vertical drain line down into the joist bay below, Now you will install a 1/4bend turning the pipe horizontal to the west. Remember to keep the quarter bend in the upper 1/3 of the joist bay to allow clearance for the required pitch drop on the horizontal line as it moves to the west. The total length of the horizontal line will be 7 and all lines under 3" diameter require a ¼" per foot drop so the total drop is 7 x ¼" =7/4" or properly 1-3/4". Code requires that all PVC must be supported within 1 of a major change in direction and at increments of not more than 48". Install a pipe hanger within 1 of the quarter bend where the vertical line changed to horizontal under the 1st lavatory. Now move 4 to the west and install another pipe hanger securing the pipe 1" lower than the output of the quarter bend. Continue running the 1-1/2" pipe until you reach a point directly below the proposed position for the second lavatory fixture arm. Make a fixture arm stub-out for the second lavatory the same length as you made the one for the 1st sink and attach a trap adapter on one end. Now attach a quarter bend on the opposite end and connect it to a 1-1/2" vertical drop down into the joist bay. Careful here. The DFU load from the 1st sink is 1DFU and the DFU load from the 2nd sink is 1DFU so the combined load on the tee will be 2DFUÂs. A 1-1/2" tee is rated for a maximum of 1DFU so you will need to use a 2" tee with a 2"x 1-1/2" reducer bushing on the top and side openings to attach the two sink drain lines to the tee. From the bottom of the tee you will install a 2" line and offset it as necessary to the load-bearing wall where you will make the vertical drop to the basement. As I stated previously, code prohibits running a vent line horizontal at any point lower than 6" below the flood level rim of the highest fixture served by that vent, however in this case the vent line is from the attic space down to the tee behind the first lavatory. From that tee the remaining line down to the joist bay and the horizontal line over to the second lavatory is technically classified as a "Vented branch" and it will suffice to "Wet vent" the second lavatory and the vertical drop to the basement. You have concluded the DWV in the bathroom and can now move to the attic to complete the vents. Up to this point we have run two vents into the attic space and under the UPC all vents must terminate through the roof however we may combine both the vents into one before making a roof penetration. Begin at the 1-1/2" vent riser above the first lavatory install a quarter bend and run a 1-1/2" line to the 2" vent above the shower wall. In colder climates where there is risk of frost closure it is best to keep the horizontal connector as close to the attic floor as possible to take advantage of residual heat through the insulation. Code requires that in regions subject to frost closure we must increase the size of the vent pipe to 3" at least 1 inside the attic space before penetrating the roof. That works fine in older homes that have poor insulation in the attic space where the attic will generally remain above freezing, but for modern construction or in older homes that have been adequately insulated in the attic space it is best to make the transition to 3" as close to the attic floor as possible. To make the connection between the two vents you will install a Tee, only this time the tee must be installed upside down so that the radius of flow on the side inlet is upward. The tee must be placed high enough to allow a ¼" per foot pitch downward from the tee to the quarter bend on the second vent line. With the two vents combined you will then use a plumb bob to mark the center of the opening on the roof decking and cut the opening. Extend the 3" pipe up through the opening and install a flashing on the roof to seal the opening weather tight. The vent line must extend a minimum of 6" above the roof, but in regions subject to snow the vent must extend to a point 6" above the height of average snowfall as defined in your local code.

It would help to know what this looked like before the renovation. My guess is that the drain/vent pipe coming out of the floor used to go straight up through a framed wall, but that wall was moved over to the left and they used this screwy way to handle the offset in the pipe. I will assume the pipe in the wall goes straight up and through the roof. What they could have done is put a long sweep L (I think that is the right fitting for a wet vent) under the floor, and jog that drain pipe over so it aligns with the vertical pipe in the wall. From there you would just tap into the vertical pipe and install fittings for a normal sink drain. To make this change would require opening up the drywall (simple task), and carefully cutting out a couple boards in the floor (a little more complicated). As I said, I'm only guessing, but maybe the previous plumbers can provide more information about the pipe routing. Bruce

Here is what I would do... Keep it about 1" off the ceiling and leave a gap to get light above the fixture to make it look like a feature. Play with the gap between the face board and the angled board until you have a bit of light coming from the top but not too much. You will not be able to see the line set and plumbing pipe unless you are 8' tall. Use some reflective material or mirror effect paint on the angled board to redirect more light down. Use integrated LED tube lights for the light source and attach it to the face board or very high on the silver surface to really hide the tube from below. This is really not an elegant solution but if done correctly it will hide the problem in something that looks like a rational and intentional design decision.

Since the vanity is between two walls, I'd purchase a cabinet with appropriate filler to fill the entire space, then have a counter templated. I wouldn't want the vanity floating in the hole between walls. Build it in, like the current one is. You can still have open shelving or legs on the bottom if that's what you like.