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Uniform Codes Questions & Answers 

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

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.

If a 1,200 CFM of makeup air is required to replenish the exhausted air of a Type I hood, can the outside air provided by the HVAC system, which is electrically interlocked with the Type I hood, be used as the makeup air for the Type I hood?

Yes. The outside air provided by the HVAC system may be used as makeup air for a Type I hood.

UPC Section 313.2 (2003/2006/2009) 312.2 (2012/2015) prohibits indiscriminate embedment of piping in concrete or masonry. What is considered adequate pipe protection? Will plastic tape wrapped around ABS provide acceptable stress relief or should some loose material be used so that the piping can move freely?

The variables involved in stress protection of piping obviously preclude fixed code requirements. Remedial procedures must therefore be field-tailored to specific installations. Because the expansion factor of ferrous metals approximates that of concrete, structural damage and settlement stresses have been the prime considerations when embedding such materials. Plastic materials ,having much higher expansion potential, require more careful consideration. Treatment of embedded longitudinal sections of plastic piping should provide for anticipated movement and freedom of branches, risers, etc., from stress and abrasion. Plastic piping passing through walls, footings and slabs should be wrapped or sleeved to provide for commensurate movement. Adhesive plastic tape wrapped tightly around ABS will afford questionable freedom and doubtful protection. Where the passage of moisture or vermin are factors, non-hardening mastic or several thicknesses of tightly wrapped 15 pound felt or comparable deterioration-resistant non-adhesive wrapping should be used. In other areas, reasonable freedom from stress and abrasion should suffice. Installation Standard IS 5 includes further pertinent information regarding thermal expansion.

In the UMC: 1. Does a passageway need 30 inches x 30 inches unobstructed clearance from the attic opening to the mechanical equipment? 2. Does “unobstructed” mean without any box outs or vertical offsets in the passageway and catwalk? 3. Are there any size exceptions to the above questions?

1. Yes, see Section 931.1 (904.11/2009, 904.10/2012). 2. Yes. The passageway must maintain the above stated dimensions but it could make horizontal or vertical offsets. 3. Yes. The largest piece of equipment in question must be able to be removed through this passageway.

Are heat trap nipples considered to be devices that may not allow pressure relief through the building supply, therefore requiring a thermal expansion tank to be installed? If so, the manufacturer's installation instructions specifically state to install the thermal expansion tank on the supply line to the water heater, which would not appear to provide any protection with the thermal nipple installed in the water heater. All information received to date specifies that thermal expansion tanks are to be installed on the cold water supply line to the water heater.

The installation of heat trap nipples should be in compliance with the condition of their listing. Note: There is evidence that similar products have been tested, however, at this time a listed device is unavailable.

1. In the UMC, does "direct exit" imply a separate exterior door from every room in the building? 2. Does "direct exit" imply a direct route of exit with maximum distance to the exterior of the building?

1. Yes. 2. Yes, a direct route would be assumed in the same room or open area within 100 feet of such an exterior door.

Are brass plated closet bolts acceptable?

The Product Certification Committee maintains that closet tank or bowl accessories shall be manufactured of a non-ferrous metal. This excludes the use of brass plated steel bolts or any other type of plated ferrous metal. The terms equally corrosion resistant material in UPC Section 408.3 (2003) 407.3 (2006/2009) 402.6.2 (2012/2015) and noncorrosive in Section 408.4 (2003) 407.4 (2006/2009) 402.4 (2012/2015) are used as general terms. It was never the intent of the Code to establish parameters of acceptable corrosion resistance for copper versus copper alloy, versus stainless steel, etc. By eliminating the use of ferrous metal (plated or not) for closet bolts, nuts, and washers, a reasonably long service life can be expected.

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