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Uniform Codes Questions & Answers 

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

1. Is an attached garage (unheated and uninsulated space with ventilation from the outside) considered a "cold area"? If so, then would a Type B or Type L vent connector be required? 2. Does the definition of "cold area" include a garage?

1. Yes, the garage is considered a cold area. The UMC requires a Type B or L vent or other equivalent means of insulation. 2. A "cold area" is defined as having or being a temperature that is uncomfortably low for humans and not heated. In summary, the object is to prevent condensation. The interpretation of a "cold area" will depend on climate and the opinion of the Authority Having Jurisdiction.

1. Are the men's and women's bathrooms in a retail store that are open to the public use required to have metered faucets on lavatories? 2. In state or office buildings where there are central bathrooms (men's and women's) which are intended to serve the transient public, are metered faucets on lavatories required? 3. What does transient mean?

UPC Section 402.4 (2003/2006/2009) 403.4 (2012) 407.2 (2015) references "transient public". In this instance the purpose is to distinguish between one element of the public occupancy and another element. Webster's Ninth Collegiate Dictionary defines transient as "temporary; fleeting; passing quickly. Metered faucets are required as the concern addressed by the code is the potential for misuse by the transient public which has no vested interest in appropriate utilization of public buildings or their facilities As opposed to employees who require extended and predictable periods of occupancy.

1. Do the requirements for UMC Section 510.7.2 apply to a building more than one story and one story building where roof ceiling assembly is required to have fire-resistance rating? 2. If yes, is it the intent of the code that other single story buildings that are not a part of Section 510.7.1 shall be governed by Section 510.7.2.1? 3. Would Section 510.7.2.3 still apply if Section 510.7.2.1 is met? (i.e. building is single story and has a enclosure of 1 hour or more and is not a building as defined in Section 510.7.1 or Section 510.7.1.1)

1. Yes. Section 501.7.2 only applies to buildings more than one-story in height and in one–story buildings where the roof-ceiling assembly is required to have a fire resistance rating as addressed in Section 510.7.1. 2. No. Section 510.7.2.1 only applies to buildings defined in Section 510.7.1. 3. Section 510.7.2.3 applies to both Sections 510.7.2.1 and 510.7.2.2. All of Section 510.7.2 applies to Section 510.7.1. If you are referring to a single-story non-rated building where an enclosure is not required, all clearances shall meet the requirements as stated in Section 507.2.1.

Can a bushing (e.g. 3" x 2") be used to increase the size of a drainline?

No. Section 311.5 (2003/2006/2009) 310.5 (2012/2015) prohibits any piping connection which "retards the flow of water, wastes, sewage or air, in the drainage or venting systems in an amount greater than the normal frictional resistance to flow." The shape and design of listed drainage fittings provide a slope when graduating from a smaller to a larger pipe size. This slope accelerates and helps maintain a steady flow of the waste products being transported. Conversely, an abrupt 90 degree drop from one elevation to another tends to dissipate the energy gained during its vertical change in elevation, as a result of the 90 degree impact at the base of the drop. Liquid will flow both upstream and downstream from such vertical impacts (which is why directional fitting are required from vertical to horizontal drainlines), with the resulting likelihood that solids will be left behind, and a greater incidence of stoppages or pipe fouling will occur. Flat-faced bushings or reducers have few appropriate applications in piping systems, whether they be DWV, water, or gas piping installations.

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.

Please explain what is meant by a wye-type fitting in UPC Section 707.7 and reconcile this with Section 706.2 which permits a horizontal drainage line to connect to a vertical drainage line by way of a sanitary tee.

The flow of waste in horizontal drainage piping is dependent on three major factors: adequate slope, reasonably smooth piping, and the proper use of directional fittings having sufficient sweep. To properly serve their purpose, cleanout extensions and their incidental fittings must also be directional and of a radius large enough to avoid abrupt turns and thus facilitate the manipulation of drain cleaning tools. For the purpose of clarifying Section 707.7 (2003/2006) 707.6 (2009/2012/2015) which stipulates that cleanout extensions must be considered as drainage piping and prescribes the configuration of fittings used, a wye-type fitting is any approved fitting embodying a change of direction not greater than a 45 degree angle. This also includes a 90 degree fitting having a sufficient radius to produce cleaning tool access characteristics equivalent to the combination of a 45 degree wye and 1/8 bend or two 1/8 bends. A tapped cleanout tee or a sanitary tee are acceptable as direct points of entry for cleaning tools. Neither of these would be permissible when a branch extension is necessary. Where a stack also serves as a horizontal cleanout entry point, a branch extending from a sanitary tee on such stack is not an acceptable extension. See also 706.2.

When using the 2 opening method in the UMC, does the code require that the entire combustion air opening 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, that is, start 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)?

No. The code would permit the opening to start above or below those thresholds and not be completely within that space.

Multi-story drainage stacks serving less than ten stories of plumbing, need not be served by a parallel relief vent stack. The question is, in a building that is nine stories in height or less, could sufficient pressures develop at the base of the vertical stacks to exceed 1 inch of water column?

While the installation of parallel relief vents for drainage stacks less than ten stories in height is not precluded, and special conditions can be qualified by Section 310.0 (2003/2006/2009) 309.0 (2012/2015), the ten story cutoff point is time-tested and adequately supported. Estimating internal pressures under various loadings in multi-story plumbing systems is difficult. The character of the waste itself, such as temperature, sudsing potential, and the size, loading, and configuration of the balance of the plumbing system, occupancy, all have to be taken into consideration. On-site manometer measurements can provide reasonably accurate criteria. Because the allowable drain loadings shown in Table 7-5 (2003/2006/2009) Table 703.2 (2012/2015), and incidentally in all other recognized plumbing standards, are predicated on only partially filled pipes, and the probability of simultaneous waste discharge decreases as the fixture unit load multiplies, the designed presence of sufficient air to permit free waste movement while protecting trap seals and maintaining system ventilation establishes a built-in safety factor.

Can return air be obtained from a corridor? How about any conditioned air? If a corridor is conditioned, does it require a separate system from the rest of the building?

Yes, air may be returned from a corridor. The intent of this code section is to isolate a required exit corridors air from any adjoining rooms air supply. The duct system could not serve the corridors and other rooms in anyway that "mix" air that could contain smoke with the air in the corridor. A separate system dedicated to the corridor would be allowed because it is not purposely conveying air to or from adjoining rooms.

Do the requirements of UPC Section 910.0 apply to industrial waste systems carrying only deionized or distilled water with traces of dissolved acids?

Yes, Section 811.0 establishes the requirements for chemical waste systems. These systems must conform to standard drainage designs regarding traps, venting, grade, cleanouts, etc. The use of a combination waste and vent that complies with the requirements of Section 910.0 would be allowed.

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