[OscarG]

I'm trying to plan DWV rough-in for a second floor "loft" space over a workshop space. Building was built about 15 years ago and never finihsed (interior). Upstairs "loft" is about 900 sq ft and intended as a vacation/weekend retreat. Located western NY state outside "city" limits.

There will be bath with toilet, shower and lavatory, a standpipe for compact wahsning machine and kitchen sink. Floorplan and "view" of stack design are shown below.


There will be 3 inlets to 3" stack San-Tee w/ L&R Inlet as follows:
A - 2" from laundry standpipe, 2" vent at standpipe
B - 3" from W.C. about 14" away
C - 2" from shower, < 5' from trap, not vented (except stack)
D - 2" from lavatory and kitchen sink, each vented

The 3" vent stack above the inlet fitting is dry and has a short 45 degree offset to move it back into wall cavity to reach attic and roof.

My understanding is that 2" horizontal run (C + D) should handle 8 units of drain. The shower (C) is 2 units and only runs a few inches combined with D into stack. Lavatory is 1 unit and Kitchen sink is 2 units making the total for D 3 units. Both lav and kit sink are vented where trap enters DWV system with san-tee.

Stack drops about 9' to sloped horizontal run to 3" PVC vertical drop which exits building below grade through concrete wall. (This was installed when building was built so location is fixed.) There is a 45 degree offset at bottom of stack to create clean-out access.

Please review and comment. Thanks!

SpeedBall1,
Truly appreciate the feedback and you make some good points. I appologize that my "art" makes a combo wye+1/8 look like a San-Tee on it's back. I know that the latter is NG.

... potential for a powerful washer pump to discharge into the lowest fixture, the shower.

I'm a little skeptical of the concern about "powerful washer pump" because washer (compact) discharges into a standpipe creating essentially a gravity fed flow. This is through a trap + san-tee + 90 degere sweep, 10 feet of pipe and another 90 + 45 degree into stack. Lots of friction to slow the flow.

Putting all the "liquid" waste into the stack upstream of the toilet could be a problem. That would drop my ceiling on 1st floor another 6 or 8 inches. Undesirable.

Alternative plan would put a combo wye+1/8 with 2" right inlet at top of wet stack. (Or San-Tee w/ right inlet. 3x3x3x2) This would accept 3" tiolet, 2" shower + lavatory into stack. Shower and Lav would "wash" toilet drain. Below that would be double wye (3x3x2x2). Input on one side would be from washer and on other side would be from kitchen sink. Both these would be downstream of toilet but would enter stack with downward flow. This plan would seperate kitchen and lav flow. It also keeps horizontal runs high (to joists) and vertical piping in the plane of stack, minimizing cieling drop.

I'll try and post a picture when I get back to scanner next week.

Comments? Suggestions?

Took another look at my plan to finish a second floor vacation loft with bath and kitchen. This revision moves the stack to a wall where I can go from ground to attic in a streight run (no jog to get around beam). It is also closer to where drain exits building.

Added a horizontal run of 3" just under joists of second floor. Can drop first floor ceiling below this run easily. Plan below shows the far end of the horizontal run where W.C. and shower connect. Ignore the green line for a moment.



The W.C. drops below joist (2x10) and turns into a 3x3x2 Wye then into a 3x3x3 Wye with 2" side entry (facing up) used as vent. The vent uses 2 - 45 degree bends to jog over in joist space to allow vent to go up inside wall to attic. One end of the 3" wye is a clean out. Other end of the 3" horizontal run enters stack at san-tee.

The 2" drain from shower goes to P-trap and then into 3x3x2 Wye. This run is 4 "pipe feet" to the vent for the toilet.

Alternative for shower drain is to turn the P-trap so it drains to the "west" and intersects a vertical vent/drain in the wall next to the shower. Drain would then turn back "east" to enter the 3" drain at the same place as shown but vented closer to shower. To me, making a U-turn with drain is less desirable than longer arm to vent.

Question 1) I'm assuming the 2" vent, described above, is acceptable for both the toilet and the shower. Correct?

Now for the green line which represents the drain from washing machine stand pipe... If I could use a double wye 3x3x2x2 where the shower drain enters the system, I could also bring the drain from the washing machine in here. This 2" drain would be vented at the standpipe near washing machine. This is a vacation residence and the washing macine is a compact unit (small size).

Question 2) Would this be reasonable place to have washer drain enter the system?

I like this design because drain from both shower and washing machine "wash" the toilet drain close to it's source.

The alternative for wahsing machie drain is to enter the 3" horizontal drain run downstram from where the toilet and shower enter the run, before the stack.

Although not shown, 2" drains from lavatory and kitchen sink are each routed to stack and enter, above the 3" horizontal run from toilet and shower, with san-tees. Each sink is vented indepependanty. (I know 2" is overkill for lav but since all others are 2" why buy smaller pipe and fittings for this short run.)

All drains are sloping 1/4" per foot.

As for vents, all go to attic and combine with 3" stack which exits roof. I assume this single vent to the outside is acceptable.

Is this a reasonable, compliant design for western NY state (farm area)?

[speedball1]

For openers you can't use sanitary tees in a horizontal position. Use a combo or wye. Would it be possible to move the toilet downstream, or the other fixtures upstream from the toilet? Having everything discharge into one fitting bothers me. Too much potential for a powerfu7l washer pump to discharge into the lowest fixture, the shower. Another thing that disturbs me is the kitchen sink and the lavatory using the same line. This arrangement might work just dandy for the first year or so but with the bends and the extra long run coupled with hair matted with grease from the soap from the lavatory plus the food particles and grease from the sink I can see nothing but blockages with this configuration in time. I can see you put a lot of time and thought into laying this out and, indeed, it's professionaly presented, but go back and think like drainage. "If I were draining down this pipe where would I hit a bend, slow down, and drop what solids I'm draining? How much backpressure or partial blockage could I take before I backed up into the shower?" Think like that and send me another lay out. Regards, Tom

[speedball1]

"I appologize that my "art" makes a combo wye+1/8 look like a San-Tee on it's back. I know that the latter is NG."

I was referring to the fitting that you have marked 3" San Tee with 2" R&L side inlets.


"I'm a little skeptical of the concern about "powerful washer pump" because washer (compact) discharges into a standpipe creating essentially a gravity fed flow. This is through a trap + san-tee + 90 degere sweep, 10 feet of pipe and another 90 + 45 degree into stack. Lots of friction to slow the flow.

We have had problems with the newer washers because of their more powerful pumps overloading the drainage systems. You show a washer discharging into a side inlet san tee and directly across from that inlet is another leading to the shower. My concerns are valid ones

I look forward to the new drawing. Regards, Tom

[speedball1]

Question 1) I'm assuming the 2" vent, described above, is acceptable for both the toilet and the shower. Correct?

No! Code forbids discharging a major fixture p0ast a unvented minor one and that's just what you're doing.
I would bring the washer in downstream from the shower. You're going to hafta vent the shower or configure the drain so it's wet vented. The washer wiil have its own separate vent won't it? Regards, Tom

[OscarG]

No! Code forbids discharging a major fixture past a unvented minor one and that's just what you're doing. You're going to hafta vent the shower or configure the drain so it's wet vented.

I see your point. Shower p-trap is now turned to the internal wall, entering a vertical 2" pipe with san-tee. Above is vent tied to others in attic, below is combo to horizontal run, cleanout at end of combo.

Will the now vented shower drain "wet vent" the toilet, allowing me to eliminate the vent circled in red? Shower vent to 3" wye at toilet is 6' horizontal run.

I would bring the washer in downstream from the shower. The washer wiil have its own separate vent won't it?

Yes, washer has its own vent, tied to others in attic. No problem, just a few extra feet of pipe and a 3x3x2 Wye. Done!

[speedball1]

Everything looks good to go to me. Unless the 2" vent downstream from the toilet's already in place there's no need for it as the shower and washer will wet vent it. Or did you plan on using it for a lavatory drain and vent. Regards, Tom

[OscarG]

Tom,
Thanks so much for your help and patience! Final design is pictured below.

The 3" stack was moved south to a wall where it could be streight from first floor to attic. Then 3" horizontal drain just under joists of second floor takes flow from W.C. shower and washer to stack. Lavatory and kitchen sink each go direct to stack for drain on separate lines. This is mostly because of your discouraging but practical remark about mixing kitchen and lavatory flow. Three extra feet of pipe and san-tee are CHEAP compared to aggravation of cleaning the drain lines just once!

Posted by Speedball1
Another thing that disturbs me is the kitchen sink and the lavatory using the same line. This arrangement might work just dandy for the first year or so but with the bends and the extra long run coupled with hair matted with grease from the soap from the lavatory plus the food particles and grease from the sink I can see nothing but blockages with this configuration in time.

The four fixture vents will tie together with the 3" stack in the attic. Only the 3" stack will penetrate the roof for vent.

As a final clarification, Tom, I think we had a misunderstanding early on... In your May 26 post you refer "to the fitting that you have marked 3" San Tee with 2" R&L side inlets" as being a san-tee on it's back, which is not allowed. This puzzled me until last night when the light came on... duh. Apparently I was not clear about the drawing being an elevation and not a floor plan. It is a view as if you were standing on the first floor (under the shower) looking east at the stack.

All in all, your comments and recommendations have moved me to learn more and arrive at a design I consider preferable to my first attempt. My original desire to keep as much as possible in the joist pockets, for esthetic reasons, was not the best thing for the plumbing. Glad to have had the benefit of your wisdom.

[speedball1]

Ya nailed it my friend!
Your plan looks good to go. You're correct I looked at the san tee as a floor plan and not a elevation one. Good luck and if we can ever be of service don't hesitate to click back in. Best of luck, Tom