See footnote 2: https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/10/traps-and-interceptors#1002.2Thank you for the reply. I was not aware that the tailpiece before the closet bend was considered part of the trap arm in the 6' limit for the WC.
I don't follow that, as the bore limit is for studs, not the bottom plate. You could cut away the bottom plate completely in a stud bay. Even in a load bearing wall, there is no load on the bottom plate in between studs. [For a shear panel, the bottom plate is important as one of the edge members.]I cannot put the reducer above the cleanout. The reducer butts up against the subfloor. The largest pipe I can run up through that wall is 2" without violating the 60% bore limit.
That is not my understanding. The following sentence is from this reference: https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/9/vents#904.1It is my understanding of the code requires the aggregate area of building vents to be sufficient to vent the building drain. By code, the vent area only needs to be half the area of the drain served.
Toilets are different. The weir is in the toilet. The trap is supposed to siphon out, and then gets refilled.The entire reason for a trap arm length limit has to do with the slope and diameter of the horizontal run of the trap arm such that top of horizontal trap arm at the vent is not lower than the bottom of the horizontal run at the trap weir because that would cut off air flow from the vent to the fixture. The tailpiece has no bearing whatsoever on the matter.
That position is completely indefensible, as R602.6.1 starts off " Where piping or ductwork is placed in or partly in an exterior wall or interior load-bearing wall, necessitating cutting, drilling or notching of the top plate by more than 50 percent of its width, a galvanized metal tie not less than 0.054 inch thick (1.37 mm) (16 ga) . .." So the requirement does not apply to interior non bearing walls; your building department is wrong.I agree with you completely about the bore limits, especially in non-load-bearing partition walls. Alas, the code is ambiguous, and in my experience, the city building department and inspectors always go with the most restrictive and onerous interpretations in cases of code ambiguity. My own city nixed my first DWV plan because they would not permit me to run a 2" vent up the extant 2x4 partition wall (non-load-bearing and not a shear wall) without bracing the bottom and top plates with 16-gauge steel reinforcing plates extending at least 6" beyond the bore on both sides.
I don't think I'm convinced by your argument as to the intention, because for small buildings with 3 or fewer WCs, the minimum required (a modifier you left out) building sewer is only 3", so your language would only require a 1-1/2" vent for the whole building. Which is incongruous with the requirement of a 2" vent for any WC.the actual intent was for it to say "the aggregate cross-sectional area of which shall be not less than that required by the building sewer as determined from Table 703.2."
It does if the house has 3 or fewer WCs. Because the requirement references the minimum required building sewer size, rather than the actual building sewer size. So with 3 or fewer WCs, the building sewer could have been 3", so you only need a single 3" vent.The original house has a 1.5" vent and a 3" vent. Ironically, that does not meet the UPC requirement.
I agree with you. The actual weir that provides the water seal is within the toilet fixture itself, and this is why the IPC explicitly excludes toilets from the requirement that the vent opening not be entirely below the weir of the trap; it is physically impossible for a toilet to meet that requirement. However, the fact remains that the sole reason for a length limit on a horizontal run of a trap arm is to prevent the top of the horizontal pipe at the vent from being below the bottom of the pipe at the upper end. For this purpose, the closet bend is generally identified as the "weir" of a toilet (even though it isn't really). The vertical tailpiece from the flange down to the closet bend has no bearing on the matter since it is not part of the horizontal run; it is the horizontal run that needs to be limited based on the pipe slope. See the linked diagram.
I think when it comes to venting requirements you're a little off on your thinking. The UPC is striving to keep the atmospheric pressure inside of the system. Since air is compressible and a toilet flushing can cause air velocity to change quite a bit, this causing possible vaccum or above atmospheric conditions.
The code is actually the minimum requirement to keep those conditions. The code is based on lab testing and consensus among people in the industry. If you have a trap that's seal is constantly being tumbled and sloshed about the threat of sewer gas is enhanced, let alone just normal trap evaporation under atmospheric conditions.
Further, imagine yourself writing a code. You have to write something (an american standard) that can guarantee public safety and stand up to lawsuits along with being practical. It's a tougher thing than it seems.
I haven't taken the time to track down lab test reports. I can only say that articles available online and written by iapmo will refer to testing done in labs. I can also say that most every time I find a problem in the field, it can be traced,either directly or indirectly, to something that wasn't quite done to code. Someone doesn't use the correct fitting or an improper vent configuration will lead to a drain slowing. Then there's the 1/4" slope. That one often times doesn't get fully implemented. People oversized pipe very often, which isn't most times explicitly prohibited by code, but I find it to underperform.I agree, that is plausible. I am not aware of any lab testing that was done to establish these UPC standards. In IPC, used internationally and by more than twice as many US states as is UPC, there is no such requirement, and the plumbing works without problem, providing an enormous volume of broad-scale empirical evidence that calls the UPC requirement into question. It should also be noted that the conventionally accepted requirement for an oversized 2" vent for a w.c. in the UPC (implied by a table footnote, but not explicitly stipulated) also is not supported by any empirical evidence since most of the world's plumbing systems use a 1.5" w.c. vent (as required by IPC) where that works just fine. I have seen no scientific studies supporting the UPC requirements. If someone has a link to a technical whitepaper with lab results that back up the UPC requirements, I would like to see it. It might be out there. However, having worked in bureaucracies, I am aware that mistaken wording and typos can become formalized as policy and afterword be very difficult to correct. I suspect that may be what has happened with the UPC. Of course, the law is the law, and what is written is written. So even if it doesn't make sense and is not supported by science or factual evidence, we must obey. We have no right to question the law here.
I agree with you. I was outraged by being required to replace the 2x4 wall with a 2x6. It creates a huge mess, it creates a lot of unnecessary waste for the landfill, it adds significant effort and time to the project, and considering that the price of building materials and disposal fees have skyrocketed this year, it adds A LOT to the overall project cost. It also requires a supplemental $50 construction permit (in addition to the separate plumbing and electrical permits) and another plan check fee, so the city makes a tidy profit for itself by forcing me to do it. I'm furious about it. But, lemonade out of lemons, it allows me to move the wall out three inches to have a little more space inside the small bathroom. As it was, the base of the shower violated the 15" standoff to the centerline of the toilet. The glass wall of the shower was clear of the standoff, which I believe should be sufficient since the spirit of the code requirement is elbow room for a person at the toilet, but the city would probably disagree and go with the strictest interpretation of the rule. They're always going to find some nitpicky way to force major reconstruction, no matter what. In response to my objections, the department representative I spoke with said, "It is because of the two-inch vent rule that we mandate a minimum 2x6 wall for plumbing in all new construction." It wasn't going to be new construction to begin with; it was just installing the fixtures into the existing space built in 1986, but now it is a huge ordeal. I really dislike my city. All of the authorities here are jerks about everything, and the fee schedules are outrageous. Tradespeople hate doing any work in this city if it requires a permit. Alas, I'm trying to be above-board and law-abiding. Big mistake!
This is awkward, but...
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