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Uniform Codes Questions & Answers
Uniform Codes Questions & Answers 

Every week we will be including additional questions and informal UPC and UMC interpretations

Does the plumbing code require that the entire combustion air openings be located within 12 inches of the floor and within 12 inches of the ceiling of the heater enclosure or does the code permit that a portion of the combustion air opening be located within 12 inches of the floor or ceiling with the balance of the opening permitted to be more than 12 inches above the floor (or more than 12 inches below the ceiling)?

Plumbing code language has never required combustion air openings to be entirely within the upper or lower 12 inches of an enclosure. Combustion air openings are required to be located at least partly within the 12 inch space above the floor and partly within the 12 inch space below the ceiling. This rule applies to louvered walls and doors as well as to individual combustion air openings.

There is a discrepancy between UMC Section 310.3 (309.3, 2009) and UPC Table 8-2 regarding condensate pipe sizing. Which is correct? If both are applicable, please explain.

Section (2003/2006/2009/2012) of the UPC states in part, "when the requirements within the jurisdiction of this plumbing code conflict with the requirements of the mechanical code, this code shall prevail," meaning Table 8-2 (2003/2006/2009) of the UPC would prevail. However, it should be noted that UPC Table 8-2 was revised in the 2003 edition to match the UMC requirements.

Can a gas water heater be located in a hallway closet where the hallway opens into bedrooms? The door on the closet has louvers.

Yes. so long as the opening is not directly into the bedroom or bathroom and the intent and objectives of the Code have not been violated.

Should we require our contractors to use metal tape to put their dryer ducts together?

No. The language in Sections 504.3.1 and 504.3.2.1 is prescriptive because of the nature of the exhaust content, thus the restriction about screening and the use of connectors (screws) that would obstruct the flow. The understanding is that a lint buildup could occur. Section 504.0 is referenced for direction on the general provisions that say, among other things, “ducts should be substantially airtight” and then refers you to Chapter 6. Section 602.4 (2003/2006/2009) says, “Joints of duct systems shall be made substantially airtight by the means of tapes, mastics, gasketing, or other means.” The committee sees these code sections as allowing quite a range of materials for sealing dryer exhaust ducts. Metal tape is certainly an option, but it would not be required. Careful examination of the manufacturer’s instructions and listings of its sealing products would indicate those suitable for the prolonged heat of a dryer exhaust.

I understand that for corrosion (electrolysis) to occur, dissimilar metals must be joined together and exposed to wet or damp conditions. The water is the catalyst for the corrosion process. Without the touching of water, steel and copper, there could not be a problem. Is it required to isolate copper piping from the steel hanger?

There is a possibility of either corrosion or electrolysis when a difference in potential exists between metals. Abrasive action caused by expansion, contraction, vibration, and the possibility of condensate generation, may result in a condition requiring some means of isolating the copper pipe from the steel hanger to prevent premature failure. For these reasons, Section 314.4 (2003/2006/2009) 313.4 (2012) 313.2 (2015) states, in part, "Piping shall be isolated from incompatible materials.

Can you clarify for us if a gas-fired steam table requires ventilation via a Type II hood?

Section 508.1 requires hoods above all commercial-type deep fat fryers, broilers, fry grills, steam-jacketed kettles, hot-top ranges, ovens, barbecues, rotisseries, dishwashing machines and similar equipment which produce comparable amounts of steam, smoke, grease or heat in food-processing establishments. The Authority Having Jurisdiction (AHJ) would have to determine if the piece of equipment produces a comparable amount of steam to warrant the installation of a Type II hood. There are several pieces of kitchen equipment available that produce varying amounts of steam. It would be difficult to say that all steam tables require a Type II hood, when there may not be enough steam escaping to be concerned. Additionally, most kitchen and restaurants move a tremendous amount of air that may be enough to compensate for small steam producing units. The decision to require a Type II hood would have to be made by the AHJ taking into account the amount of steam being produced by the equipment and the design of the air moving system serving the space.

Does Section 311.4 (2003/2006/2009),310.4 (2012/2015)expressly prohibit Single Stack Drainage and Venting Systems?

Section 311.4 (2003/2006/2009), 310.4 (2012/2015) prohibits the installation of "single stack drainage and venting systems with unvented branch lines " Section 301.2.2 (2003) 301.2 (2006/2009/2012) 301.3 (2015) states, "The Authority Having Jurisdiction may approve any such alternate provided that the Authority Having Jurisdiction finds that the proposed design is satisfactory and complies with the intent of this Code." It is the intent of this code that every trap be protected by a vent to guard "against siphonage and to ensure air circulation" throughout all parts of the drainage Section 1004.0 (2003/2006/2009/2012/2015) prohibits the use of "S" traps. None of these basic plumbing design provisions are possible when "unvented branch lines" are installed. In summary, modern waste and vent systems have evolved from the one pipe systems of the late 1800's because science and empirical evidence have shown what works and does not work well. Meeting the intent of the UPC and modern plumbing system design cannot be achieved by installing oversized, unvented "S" traps as an "alternative" system. Opting for such systems simply ignores standard plumbing concepts which have been developed and proven during the past 100 years.

Is the exhaust airstream from an enclosed parking garage to be considered “environmental air” or “product conveying air”?

The exhaust from an enclosed parking garage is considered product conveying air since these exhausts routinely convey exhaust products containing carbon monoxide and smoke. Additionally, since garage ventilation systems may also be required to dissipate fumes from vehicular fuel spills, it is recommended that they should be regarded as ducts conveying flammable vapors. See also UMC Answers and Analysis Section 506.9.1, Vent Termination.

When installing a floor sink, which an indirect waste from a commercial sink drains into, should the floor rim flange of the sink be placed on top of the finished floor or set flush with the finished floor?

The UPC does not require elevation of receptors to prevent the tops of their flanges from being flush with the finished floor. Nonetheless, specific conditions may justify local authorities requiring receptors to be installed as to prevent unintended waste collection from other than the intended primary fixture. See also 408.1 and 408.2 (2003) 407.1 and 407.2 (2006/2009) 402.0 (2012/2015)

Section 510.5.2.2 does not permit the use of a flanged with edge weld or flanged with filled weld. Would this method be allowed in the UMC as Figures 5-6 a, b, c, d clearly allow the use of a flanged connection that is no different than the welded flange?

No. The 2006 UMC only allows overlapping duct connections of either telescoping or bell type for welded field joints. The examples used in UMC Figure 5-6 (2003/2006/2009) are to be used only in a duct-to-fan connection. The reason for the limitation is to prevent pocketing of grease in the duct that could result in excessive accumulation of grease.

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