How do I make this s-trap legal?

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bruceg

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My bathroom sink contains an s-trap, see attached picture.
Is it possible to make this setup legal?
Is an s-trap configuration with an Air Admittance Valve legal?
Other suggestions?
I live in PA.

Thanks,
Bruce
 

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The solution looks simple enough.
The drain pipe coming out of the floor is 1-1/4 inches,not 2 inches.
Do you see any issues.

Thank you,
Bruce
 
918.3 Where Permitted

Individual, branch and circuit vents shall be permitted to terminate with a connection to an individual or branch-type air admittance valve in accordance with Section 918.3.1. Stack vents and vent stacks shall be permitted to terminate to stack-type air admittance valves in accordance with Section 918.3.2.

918.3.1 Horizontal Branches

Individual and branch-type air admittance valves shall vent only fixtures that are on the same floor level and connect to a ''horizontal branch drain'''. Where the horizontal branch is located more than four branch intervals from the top of the stack, the horizontal branch shall be provided with a relief vent that shall connect to a vent stack or stack vent, or extend outdoors to the open air. The relief vent shall connect to the horizontal branch drain between the stack and the most downstream fixture drain connected to the horizontal branch drain. The relief vent shall be sized in accordance with Section 906.2 and installed in accordance with Section 905. The relief vent shall be permitted to serve as the vent for other fixtures.

918.3.2 Stack

Stack-type air admittance valves shall be prohibited from serving as the vent terminal for vent stacks or stack vents that serve drainage stacks having more than six branch intervals.

918.4 Location

Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented. ''Stack-type air admittance valves shall be located not less than 6 inches (152 mm) above the flood level rim of the highest fixture being vented''. The air admittance valve shall be located within the maximum developed length permitted for the vent. The air admittance valve shall be installed not less than 6 inches (152 mm) above insulation materials.


What Diehard submitted will work but is not code. UNLESS the AAV is ABOVE the flood level of the fixture and accessible
 
Sorry frodo but it doesn't say that.

It says, "Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented.

You may have been looking at Stack-type AAV's.

AAV's are located below sinks all the time.
The key is to get them as high up as possible but still be able to access them to change them out if necessary. Ideally they would be above the flood level, but that is not always possible.
 
Is the AAV needed for code if the horizontal pipe for example is 6"?
My sink is approx 3 feet from the main house vent pipe.
upload_2020-2-24_6-15-40.png
 
The problem is, you're dropping down after a trap. Even with a p-trap, by dropping down without a vent, is in itself creating an S-trap.
Diff looking S-traps.jpg
In the absence of a vent, it is possible that a full pipe of water would siphon the trap seal. The whole purpose of a vent for a trap is to prevent that.

If the horizontal pipe (trap arm) that you are pointing at was say 6", you may be less likely to siphon the trap seal but a vent is still required by code.

As @Zanne pointed out, "get them as high up as possible but still be able to access them to change them out if necessary."
 
I understand from your statement "Even with a p-trap, by dropping down without a vent, is in itself creating an S-trap."
Since my house is 80 years old, do I need to update every sink trap to have an AAV?
Also, are you implying that every new house construction with an s-trap has an AAV beneath each sink.

Thanks,
Bruce
 
I understand from your statement "Even with a p-trap, by dropping down without a vent, is in itself creating an S-trap."
Since my house is 80 years old, do I need to update every sink trap to have an AAV?
Also, are you implying that every new house construction with an s-trap has an AAV beneath each sink.

Thanks,
Bruce
There are no S-traps in a new house. Or at least, shouldn't be.
Typically the vent PIPES are in the walls and is a far better design than using AAV's.

In my State, "Air Admittance Valves are not permitted, except with Special-permission from the Board." Although they are acceptable.
 
I am learning a lot from this message board.

My house has two vent stack pipes sticking up out of the roof.
All of my plumbing fixtures are located near the vent stack pipes.

In my house, I have S-traps, P-traps and a drum trap.
  • I plan to change the S-traps to P-traps and add an AAV.
  • I plan to leave the existing drum trap alone.
  • I plan to leave the existing P-traps alone.
    Your statement "Even with a p-trap, by dropping down without a vent, is in itself creating an S-trap." is very powerful and interesting.
    Not knowing what is behind a wall, then I might say a majority of P-traps are pseudo S-traps.
Thanks,
Bruce
 
Yeah it's tough to know if you have a vent pipe in a wall.

If you haven't experienced any sewer smell, which would be the case if a trap lost its water seal, that's a positive thing.
 
Let's clarify "illegal" and "not up to current code". Just because you have an "S" trap does not mean you are "illegal"; nobody is going to give you a citation or fine or take you to jail. There are millions of homes in the older housing stock in the USA with S traps, inadequate venting, electrical systems w/o grounds, and so much more. Heck, watch all those HGTV shows and it seems half the homes they work on have "knob and tube" wiring, or collapsed fiber sewer lines or some other inadequate thing that wouldn't be done today...because we've learned as time goes on.

My home, that I lived in for 27 years, had only ONE roof vent penetration; all the plumbing venting for the entire home's set of fixtures came up to the attic and connected to that one vent. It surely met code at that time, and the builder didn't like multiple roof penetrations. Sure it was a bit of extra PVC in the attic but PVC then as it is now is very cheap; roof penetrations are not and are always subject to leaks. The fewer the better; that was the builder's philosophy.

That being said, I made a number of renovations to that home, and always added an AAV. In my second home, when I added a slop sink in the garage, I added an AAV; when I renovated the kitchen, I added an AAV; ditto for the laundry room. I mounted the AAV's as high as possible but accessible. I don't know if they were needed or not, but it cannot hurt to have them. There's no such thing as "too much venting" in a plumbing system, but there sure is inadequate venting!

The "problem" with "venting to code" as it were, is that proper venting generally requires pipes within walls. Unless you have an unlimited bank account, and love to tear down drywall, etc. added venting to code sometimes is nearly impossible in an older home...
 
My house is 80 years and has its share of not up to current code issues (outlets with no grounds, S-traps). I do not have any drain issues other than S-traps in a few of my sinks. I plan to move in a few years and want to be proactive and update what is required to sell my house. From what I read online, S-traps are not legal and should be converted to P-traps with an AAV, home inspectors look explicitly for S-traps.

I plan only to update my sinks with S-traps. Since my sink drain pipe is almost directly above the drain pipe coming out of the floor, I will need to add a few to horizontal pipes to accommodate the P-trap and the AAV. Hopefully there are no issues adding the horizontal pipes.
 
My house is 80 years and has its share of not up to current code issues (outlets with no grounds, S-traps)....from what I read online...home inspectors look explicitly for S-traps.

That may be--but they look for ALL kinds of things that are not up to [current] code and merely report to the person ordering the inspection what these things are. Absolutely, positively guaranteed if you have an electrical system with no grounding that will probably be far more of an issue for you when you come to sell the home. Grounding is one thing, but in many areas things like GFCI and AFCI outlets are required in many places throughout the home--and if you have no grounding you can't really install these effectively. Good work on getting the S-traps replaced, but sit yourself down when that inevitable inspection report comes in about electricity some point in the future!!
 
I was told in the past by a certified electrician my electrical system would be acceptable.
  • All non-grounded outlets are two-prong.
  • All grounded outlets are three-prong.
  • Outlets near water and outside are properly grounded GFCI outlets.
  • Circuit breaker panel
I am addressing my sink trap issue now simply because I saw the following on YouTube.

 
If your sink is only 3' away from the main vent, why not try to tap in to it? You could create a branch vent either in the wall or outside the wall and then go in to the wall and merge with the main vent.
 
From what I read, I believe my sink is installed as a direct-vented plumbing fixture, thus does not usually require its own plumbing vent piping.
Trying to tap into the main vent is way above my skill level.
I would need to remove part of a plaster wall and be able to tap into a cast iron stack vent.
Instead, when I have time, I plan to change the S-trap to a P-trap and add an AAV as suggested.


Definition of Direct Venting of Plumbing Fixtures


Basically,larger piping diameter allows longer distances between a plumbing fixture and its vent stack. If a plumbing fixture is located too far from the main building vent stack, then its own drain pipe must have its own vent stack connection piping.

But if a plumbing fixture is close enough (five feet or less) to the main waste stack pipe (vent), the fixture does not usually require its own plumbing vent piping, and it is considered a direct-vented plumbing fixture.

Of course this rule presumes that the drain piping between the fixture trap and the waste stack is properly installed and properly sloped.

The usual slope on the fixture drain piping is 1/4" of slope per 12" (foot) of horizontal distance or "run" of piping.​
 
Most houses do not have a vent stack. That is for commercial buildings. It used to be, attach everything to the main stack in the house and that was ok. Now you cannot attach a drain to a stack unless it has a vent above the flood level of the upper floor. An example would be adding a bathroom on an upper floor directly above another bathroom and wanting to use the lower floors 3" stack for the drain. Its only usable if you extend the vents from the lower bathroom above the flood level of the upper(new) bathroom.
 

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