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Noth Jersey
06-30-2010, 11:52 AM
Am I mistaken, or does the following language permit the use of an s-trap?:

12.8.1 Venting of Fixture Drains
Fixture drains shall have a vent so located that the vent connects above the top weir of the trap and the
developed length of the trap arm is within the limits set forth in Table 12.8.1.

EXCEPTIONS:
(1) Water closets and similar siphonic fixtures.
(2) Combination waste and vent systems. (see Section 12.17)
(3) Vents may be connected below the top weir of the fixture trap if the following conditions are met:
a) The vertical section of the drain pipe shall be at least one pipe size larger than the trap inlet size.
b) The horizontal pipe connected to the trap outlet shall be at least two pipe diameters long.
c) The developed length of the trap arm shall not exceed the values in Table 12.8.1.

hj
06-30-2010, 11:55 AM
It appears to be what it says, but I would question whether it is what its intent is.

Noth Jersey
06-30-2010, 01:19 PM
What do you think they're going for? If I could drop below the floor before I vent, I could avoid butchering a kitchen cabinet and losing a bunch of storage space. I was thinking I could meet the exception by putting 2" traps on my sink and my disposal, since the inlets would be 1-1/2".

On a different note, can I use the elbow that came with the disposal and put a p-trap on each fixtures, or should I make a straight shot to a sanitary tee connected to the sink tailpiece? I kind of got the impression from something Terry wrote that the disposal elbows should be avoided.

Terry
06-30-2010, 04:17 PM
Most plumbers will use a disposer kit and one p-trap. The disposer kit comes straight off the disposer.
We use the supplied 90 on single bowl sinks.

I worked on a kitchen sink the other day that had three p-traps. The third trap for the dishwasher was so full of gunk that the dishwasher could no longer drain.
I cut out the three traps, took out the supplied 90 and ran everything with one trap. Now she can use her dishwasher.

I don't know why anyone would revert back to old style plumbing. There was a good reason we quit doing things that way.
On the job above, one of the complaints was kitchen smell. Does a smelly kitchen sound good to anyone? Or is it just me?
I like smell containment.

Doherty Plumbing
06-30-2010, 04:47 PM
What do you think they're going for? If I could drop below the floor before I vent, I could avoid butchering a kitchen cabinet and losing a bunch of storage space. I was thinking I could meet the exception by putting 2" traps on my sink and my disposal, since the inlets would be 1-1/2".

On a different note, can I use the elbow that came with the disposal and put a p-trap on each fixtures, or should I make a straight shot to a sanitary tee connected to the sink tailpiece? I kind of got the impression from something Terry wrote that the disposal elbows should be avoided.

You don't need a 2" trap you need the VERTICAL section of the drain (IE after it connects to your vent) to be 1 size larger then your trap inlet size.

Noth Jersey
06-30-2010, 04:50 PM
Terry,

I was contemplating individual p-traps based on this fellow's theory:

http://www.nettally.com/palmk/GDplumbing.html

What's wrong with his line of thinking? Does the baffle in the disposer kit constrict drainage that much?

Doherty Plumbing
06-30-2010, 04:55 PM
Terry,

I was contemplating individual p-traps based on this fellow's theory:

http://www.nettally.com/palmk/GDplumbing.html

What's wrong with his line of thinking? Does the baffle in the disposer kit constrict drainage that much?

If you have two traps wouldn't you either need:

A. Both traps protected by their own vet,
B. Both traps connect to their shared vent via a double fitting so that each trap is connected to the vent symetrically?

I would think with 2 traps tied togeather like that, and one of the traps constantly has rushing water going through it, that you'd tend to siphon the sink's trap dry when the dishwasher is draining.

Up here a setup like that would be against code.

Noth Jersey
06-30-2010, 05:22 PM
You don't need a 2" trap you need the VERTICAL section of the drain (IE after it connects to your vent) to be 1 size larger then your trap inlet size.

Couldn't I just make everything downstream of the trap 2"?

Whatever the case, does this code provision sound practical?

Based on the exception I could run the drain down through the floor (long sweep, sanitary 1/8, sanitary 1/4?) and jog horizontally to the vent as long as:

1) I size up the vertical drain one pipe size
2) I make a 3-4" (twice the pipe diameter) horizontal run out of the trap outlet before turning down
3) I keep the developed length (whatever that is) of the trap arm under 8 feet for a 2" drain and under 5 feet for a 1-1/2" drain (see table 12.8.1 in http://www.phccweb.org/files/Depts/Technical/2006NSPCNonIllustratedWeb.pdf)

Terry
06-30-2010, 06:39 PM
Plumbers don't run two p-traps on the same trap arm.
We wouldn't be able to sneak that by a plumbing inspector. And there is a good reason why.

As a side note, if your disposer isn't grinding well enough to drain through a baffle tee, it's old and worn out. It's time to replace the disposer.

Noth Jersey
06-30-2010, 08:15 PM
I'll refer the author of that page to this thread. So, the idea is that water rushing through the wye from one fixture would siphon out the p-trap on the other, correct?

Any thoughts on the s-trap exemption in the NSPC?

Doherty Plumbing
06-30-2010, 09:37 PM
I'll refer the author of that page to this thread. So, the idea is that water rushing through the wye from one fixture would siphon out the p-trap on the other, correct?

Any thoughts on the s-trap exemption in the NSPC?

Correct.

As to why they all s-traps who knows....

Noth Jersey
06-30-2010, 10:14 PM
Going up a size and tying into the vent within about four feet should prevent of siphoning, right? Would you size it up just one size, or would you go to three inch on that vertical piece? :) Thank you for the invaluable information!

MACPLUMB 777
07-01-2010, 06:00 AM
The proper way to run pipe is 2" vertical with a 2"x11/2"x11/2" tee on top !

That way you have 11/2" for trap arm and 11/2" vent up with a 2" drain out

Noth Jersey
07-01-2010, 06:42 AM
The unfortunate framing of my kitchen area would end up killing a lot of cabinet space in a small kitchen (2x4 framing, sink under the window, rim joist close to the center of the bottom plate, difficult spacing of the stud bays). If I can design an S trap that won't break the p-trap seal under the worst conditions, we'll be in good shape. I'm sure a 6" drain would do the trick, but I'll bet the threshold at which siphoning takes place is at least a couple pipe sizes smaller. I'm counting on giving up most of the space in my sink base, so I don't mind running a large drain if necessary.

My main question is whether or not an increase of one pipe size and proximity of the vent would provide a viable system. The code doesn't appear to present a problem in this case, but siphoning would be unacceptable.

The reason for the 2" vent is to accommodate the washer and laundry tub in the basement.

Update: I just got off the phone with the inspector. My interpretation of the code is correct except for the size of the trap. If I don't want to go up to 3" for the trap arm and the rest of the drain, I need a 1-1/2" trap, sizing up to 2" on the outlet. The 1-1/2" size trap means that I have five feet to hook into the vent. For anyone else in New Jersey or Maryland (the only two states that have adopted the NSPC), this information should come in handy. According to the inspector, a 2" trap arm/drain is sufficient to avoid siphoning on a 1-1/2" p-trap. Can anyone corroborate with a real-life anecdote?

Terry
07-01-2010, 08:17 AM
What you describe on the framing is normal framing. We manage to plumb correctly under those circumstances daily.
A plumber would have it done in less time that it takes to type this. It's that easy.

Do you want pipes coming up through the cabinet taking up space?
It seems a shame to cut up a new cabinet for a pipe that shouldn't have been there.
The finish carpenter is going to love you for making his job harder.

It sounds like you have it handled with the inspector though.

Noth Jersey
07-01-2010, 08:58 AM
What you describe on the framing is normal framing. We manage to plumb correctly under those circumstances daily.
A plumber would have it done in less time that it takes to type this. It's that easy.

Do you want pipes coming up through the cabinet taking up space?
It seems a shame to cut up a new cabinet for a pipe that shouldn't have been there.
The finish carpenter is going to love you for making his job harder.

I am the finish carpenter. :) I'm actually interested in learning the proper technique for my personal edification, so if I've missed an easy solution, I want to learn.

Plumbers typically aren't interested in doing small increments of work, and rightly so, without charging me a hefty flat fee per service call. The nature of my remodel is such that the plumbing, flooring, and the drywall must be done in small increments.

With a standard installation, I would have to punch a hole into an adjacent cabinet, saw a large hole for the 45 degree vent (I need to offset because I can't shoot straight through the sill plate without cutting a 1" deep channel down my rim joist), and punch a hole for the drain line through the bottom of the adjacent cabinet.

I could also run the trap arm through three cabinets and into a bearing wall, but I believe this wall sits directly on the main girder.

Going straight out the back of the sink base cabinet is not possible because the window sill is built up with horizontally stacked 2x4s to accommodate a window that was significantly shorter than the original rough opening. Even if we had cripples below the window instead of solid wood, I'm not sure I could get the vent up to 42" before going horizontal. I would also have to put a 2" hole through 2x4 king and jack studs, which would require some sort of Simpson tie reinforcement.

If I'm missing a really obvious solution, please let me know. I would prefer to keep all the pvc in one cabinet and drill a single hole in the cabinets.

Ian Gills
07-01-2010, 09:00 AM
a 2" trap arm/drain is sufficient to avoid siphoning on a 1-1/2" p-trap. Can anyone corroborate with a real-life anecdote?

A lot is to do with the distance between the trap and the vent. I have a 1.5 inch p-trap on a 1.5 inch pipe for my laundry tub. But it is just over 42 inches away from the vent. The trap gulps after the tub has drained. I am going to have to shorten the distance.

If you have just shy of five feet of pipe between your trap and your vent then you will need 2 inch pipe. Any more than 5 feet and you will run into the same problems as me.

Although Table 12.8.1 shows something different. Where am I going wrong here?

Noth Jersey
07-01-2010, 09:30 AM
Well, the table specifies lengths based on the trap arm size (1-1/2" in my case). A 1-1/2" trap corresponds to a developed length of five feet. If the drain is horizontal until you hit the sanitary tee for the vent, you should still have 18 inches to remain code compliant. In fact, according to the table, 42 inches should be fine for 1-1/4". Are you dipping below the crown weir before you tie into the vent? You can have up to 3 DFUs on a horizontal drain, and I believe a standard laundry tub counts for two. I'm not a pro, so I'm not the best one to help you troubleshoot, but I would make sure your vent is clear of obstructions and that the p-trap is not reversed.

MACPLUMB 777
07-01-2010, 11:23 AM
I would follow terry's recommendation come out of the top of the tee 90

over below your

stacked wood, then outside the window space 90 up though the roof is

how real plumbers would get it done,

or install aav on top of the tee as high as possible

Noth Jersey
07-01-2010, 11:54 AM
Mac,

The trouble is those stacked 2x4s start at about 38 inches above the finished floor. I'm pretty sure the inspector will not allow me an exception from the requirement to keep that horizontal vent six inches above the flood rim of my fixture. In NJ, we have to have an engineer design the AAV. He might allow me to augment the combination waste-vent type installation, but I'm a little reluctant to introduce a mechanical vent that will one day fail and introduce sewer gas into the house. Do you know of an AAV with some sort of fail-safe, i.e., it automatically closes off when it fails?

Terry
07-01-2010, 05:11 PM
Which ever way you go, could you post some pictures when done?
Terry

SewerRatz
07-01-2010, 05:42 PM
Hi guys. Here in Illinois it is against code to run the disposal into a end waste and use a single trap. Each fixture has to have its own trap. The way we do it is a 2" line in the wall come out with a 1 1/2 double Wye. The center of the double Wye would be the clean out, then each side of the double Wye would have a trap. So the picture here is not that far off base to what meets the Illinois plumbing code.

http://www.nettally.com/palmk/DoubleSinkDrain.jpg

Noth Jersey
07-01-2010, 07:14 PM
Which ever way you go, could you post some pictures when done?
Terry
If I'm ever done, I'll gladly post some pictures. :)


Hi guys. Here in Illinois it is against code to run the disposal into a end waste and use a single trap. Each fixture has to have its own trap. The way we do it is a 2" line in the wall come out with a 1 1/2 double Wye. The center of the double Wye would be the clean out, then each side of the double Wye would have a trap. So the picture here is not that far off base to what meets the Illinois plumbing code.



Terry and Doherty tell me the type of installation in the picture will result in siphoning. Have you ever experienced this phenomenon with your double wye configuration?

SewerRatz
07-02-2010, 08:53 AM
If I'm ever done, I'll gladly post some pictures. :)


Terry and Doherty tell me the type of installation in the picture will result in siphoning. Have you ever experienced this phenomenon with your double wye configuration?

Nope never had an issue. As I said its allowed here in Illinois. Its best to check with your local plumbing inspector to see what meets the code by you.

Noth Jersey
07-02-2010, 10:53 AM
Why not disconnect the p-trap at the union for a cleanout? What's the benefit of the double wye?

Terry
07-02-2010, 11:00 AM
There always needs to be a cleanout on a kitchen sink.
The double wye makes sense too. One trap doesn't run by the other like in the first drawing, it's more like a double fixture fitting in that the arms come in equally and not by each other. The cleanout in the center would be the same in other codes as the clean out either on the arm or on the vertical below.
Kitchens need cleaning out more then most other fixtures because of the grease, and from the disposers.

Noth Jersey
07-02-2010, 01:34 PM
Here's a related thread: http://www.terrylove.com/forums/showthread.php?36767-Single-to-Double-Sink-Vanity-%28again%29

Here's the relevant NSPC excerpt on the other thread:
http://www.terrylove.com/forums/attachment.php?attachmentid=10860&stc=1&d=1277066914

I believe exception number 3 indicates that the end outlet continuous waste fitting is acceptable.

Terry
07-02-2010, 01:42 PM
It would seem to be true, however we always have to look at the local inspector and please him or her.

Years ago, I plumbed seven meat markets for a large chain. Since the stores were located in different cities and counties, I had to meet with each local inspector to find out how I was going to pass inspection. Everything was supposed to be UPC code, however I wound up plumbing each one differently.

Noth Jersey
07-02-2010, 02:30 PM
Those prima donnas. :D

Noth Jersey
07-12-2010, 01:14 PM
I think the branch vent below is very dubious, but how does the rest of the sketch look?

11009

Noth Jersey
07-12-2010, 08:41 PM
The inspector didn't allow that connection below the flood rim, even though the ejector would prevent a backup in the event of a clog. I guess a foolproof system is the way to go. I'll just have to tie into a different vent group where I can connect at an appropriate height above the flood rim.

The inspector also told me that he wanted a 2" vent for the ejector, but I think the applicable code says 'the sump for macerating toilets shall be vented with a 1-1/4" pipe.' (NSPC 11.7.10) The manufacturer's guideline for my pump is 1-1/2", and my system is a self-contained SaniFlo unit that is designed to sit above grade. The inspector is the type of guy who seems pretty open to feedback, but I don't want to risk burning any bridges on a fairly minor issue. I may need to rely on his generous spirit if I ever try to expand my septic system.

Noth Jersey
07-19-2010, 07:28 AM
The inspector ended accepting the manufacturer's instructions (1-1/2" vent) becaue the SaniFlo is more like a macerating toilet than an ejector pump.