DWV Plan for Loft Space

This is my second attempt at major DWV project so I am looking for advice on my design. This is for adding bath, kitchen and compact washer to second floor "loft" space over an existing shop area. Building was built about 15 years ago and never finished. Now looking to make it livable for weekend/vacation get-away. There is no other plumbing in the building.

Floor plan is


DWV Stack is moved to the east wall (where I discovered I had space above a solid beam to get "under" the second floor wall) of plan where VIEW is marked. Design goal was to keep all west to east horizontal drain lines above or very close to joists. All 2" drains achieve this goal except where they enter stack which is OK. W.C. drops below joists but is only a short run to stack. This was necessary to allow 3" vent above the San-Tee w/L&R Entry to angle 45 degree to get into wall cavity. 3" vent above this fitting is dry! New stack plan is


(PDF drawings deleted)

A is 2" drain from washer stand pipe which is vented at far end.
B is 3" drain from W.C. about 14" away.
C is 2" drain from shower less than 5' away from P-trap at shower pan. No venting except 3" stack.
D is 2" drain from lavatory and kitchen sink. Each has its own vent since kitchen sink is about 6' upstream from lavatory.

From what I have read 2" DWV horizontal can handle 8 units. C+D, where they enter stack are 2 units (shower), 1 uint (lav), 2 units (kit sink) TOTAL 5 units (and 2 of them from shower only go a few inches into stack).

There is 3" vent to attic/roof above San-Tee w/L&R Inlet (3x3x3x2x2). Dry above. Stack feeds down to horizontal run going south to exit from building, through concrete foundation. (The exit pipe was preinstalled before they cast foundation.)

Would appreciate expert/experienced comments and suggestions on this REVISED design.

One other note, this building is in western NY state, outside of "big" city code requirements. I had received a comment about some inspectors rejecting the San-Tee w/L&R Inputs but I don't think this will be a problem.

One other note, this has been a great learning experience!

Thanks in advance!

A lot to digest; a 3rd page in your PDF has a third page has even more comments in it. Oscar, I'm going to kick the ball once now, assuming I have understood enough of what you have drawn, and assuming that Master Plumbers will comment after me.

First, a minor point. I assume you meant the diameter of the last pipe to be 3"; you drew it as 2". Second minor point: you have included no information about the existing plumbing in the rest of the building. Why? Now come the bigger questions.


1. Connecting to a new stack

1a.) The plumbing as now drawn, shows a toilet and an unvented shower both being combined and then both sending waste down a stack, all unvented until the Double Wye. Not optimal.

1b.) The washer gets a 2" vent right at its P trap and then a 3" vent before it connects to the stack. More than necessary.

I'd think through a way to balance the use of these two vents more equally, perhaps by using the 3" vent for the toilet and shower before they connect at the stack with that SanTee, so that the stack itself gets vented.


2. As drawn, the pipe for the sinks cuts through a series of 2"x10" joists right against the load bearing wall (where the joist is supported, at the load bearing wall). You could cut holes farther away from the joist end. This reduces weakening the shear strength of the joists. How many inches away depends on how long the joists run between two load bearing walls.


3. Consider making the neo angle shower 2" longer on each of its long walls; it won't bother anyone sitting on the toilet.
3b. - Consider setting the toilet on an angle. Eljer makes a corner toilet whose tank is a triangle, if you wanted to squeeze it back into the corner. Or you can custom build a storage unit in that corner if you turn a regular-tank toilet a full 45 degrees. Then you'd even have space to bring the 3" vent into, and that would let you insulate that outside wall against winter cold and summer heat much better. You can also put the 2" vent in the kitchen-bathroom separator wall if you wanted to insulate the outside wall more at that spot.
3c. - Consider creating a neo angle shape for the bathroom sink and vanity area. Then you can have a rectangular cupboard for linens in the remaining space left over, your vanity takes the whole width right now.


david

geniescience (David), thanks for quick feedback! Unfortunately, my drawings do not fully document the situation. Did find a picture of the second floor "space" which may help.

First, a minor point. I assume you meant the diameter of the last pipe to be 3"

Click to expand...

I intended as 2" based on 1 unit for Lav and 2 units for Kitchen sink, thinking there was sufficient capacity to drain in 2" pipe.

Second minor point: you have included no information about the existing plumbing in the rest of the building.

Click to expand...

At this point there is no other plumbing. The building is an unfinished shell. Only possible addition would be a slop sink on first floor. The point of exit from building was based on the "stuff" flows down hill rule to get to septic (to be built) and avoid clearing too many trees.

1a) I agree, not optimal but toilet is close to stack and shower could be vented at P-trap. Simply adding this vent to shower would probably improve both and at just under 5' it is at the limit of it's length w/o vent. I don't think there is a problem with too much venting.

1b) Washer is vented at P-trap because horizontal run is well over 5' from stack. It feeds into the 3" vent to avoid cutting/drilling joist or dropping below joist.

2) Actually, the 2" drain (south to north run into stack) hangs just below the joists. Drawing does not show this very well at all. The run from kitchen sink to lav is drilled through non bearing wall 2x6 stuts and does not drop below the joists until very close to the east (bearing) wall.

3a) Absolutely agree with bigger neo-angle shower.

3b) Budget is an issue so very standard toilet is preferable. Width is at least 34" so encroaching with a 2" bigger shower is not a problem.

3c) Full width vanity counter (~6') is my preference. Storage cabinets below and smaller "cubby" cabinets in corners above. (There is also more linen storage planned near washing machine.)

Hopefully this clears up some of the lack of clarity in drawings. Thanks again for comments!

I'm going to have to let master plumbers comment next, as I'm reaching the limit of my specific knowledge. I think they will tell you that prior to turning a drain downhill, it needs venting, unless it's going into a vented stack, not just a stack. So these two drains have to be vented.

OscarG said:

shower could be vented at P-trap. Simply adding this vent to shower would probably improve both and ...

Click to expand...

Whether this suggestion is good, or the best, i will leave that to the next few people who post.

david

Revised Plan

Revised the plan above based on finding a better fitting...
https://terrylove.com/forums/showthread.php?t=13191

Now all seems to be vented correctly!

wow. Oscar, send private messages to a few master plumbers here to see if they will come over and comment. Now that you've edited your drawings, my comments may not make sense but that is fine.

here is one new comment: can you move the corner vent closer to the laundry so that the angle when it all turns to the stack is now 135 degrees instead of 90 degrees? Can you do the same move operation with the other drain coming in from the shower and sink? This makes the last turn a 135 degree bend not a right angle. That's a 1/8th bend instead of a 1/4 bend, using drain fitting terminology.

david

geniescience (David), Thanks again for the comment. I knew my original design was kind of flakey but then found a picture indicating I did have a "pocket" to route the 3" vent into the new location. My recolection was there was a solid beam in this location that forced the vent as I originally placed it. This along with new fitting solved a lot of problems!

can you move the corner vent closer to the laundry so that the angle when it all turns to the stack will be 135 degrees instead of 90 degrees?

Click to expand...

Not sure the location of corner vent has much to do with what you are suggesting. I do, however, recognize your suggestion of using 1/8 bend(s) will "streighten" the flow into the stack. Using 2 pieces of 1/8 I can transition horizontal west-east run to horizontal north-south run into stack while dropping the few inches necessary to get under joist. Good plan ! (...and similar set up will probably work for shower drain too.)

Despite what floor plan shows drain/vents for laundry, lavatory and kitchen will all be vertical with san-tee for ptrap or stub entry. Drains will drop through floor to combos wye-1/8 bend transitioning to horizontal runs (in 1st floor cieling) to stack. Combos are used to install cleanout at high end of horizontal drain runs (even though not required). A couple bucks for fittings is cheap even though they may never be opened.