UNFORM CODES QUESTIONS & ANSWERS

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

A replacement water heater in a residence was installed inside a utility room, located approximately 12 to 15 feet from the building exterior. The building construction is a conventional raised floor with a crawl space. The water heater is installed in a pan. The temperature and pressure relief valve terminates into the pan which is drained into the crawl space. The Code states that the pan shall drain to an approved location. Can the pan drain into the crawl space, as opposed to being piped to the building exterior?
- Discharge piping from any source may not empty into the crawl space beneath a building. All discharge piping shall terminate outside the building or to an approved receptor located within the building. The drain must terminate in a visible location. Note: The pan serving the water heater is not an approved receptacle for the T&P valve. The Code does not intend that a 3/4 inch pressure pipe (relief valve) be discharged into a receptacle which is equipped with a 3/4 inch gravity drain (drip pan).
Do evaporator coolers fall under the regulated air moving systems that may require automatic shutoff under UMC Section 608.1?
- Yes. Evaporative cooling systems used to provide supply air to enclosed spaces of buildings fall under the 2018 Uniform Mechanical Code Section 608.1. It requires an automatic shutoff when the velocity of the supply air produced exceeds 2,000 Cu. ft. per minute (unless the criteria in one of the exceptions listed in 608.1 is met).
Does the UPC allow the use of waterless trap seals on floor drains in commercial and industrial buildings?
Are waterless trap seals allowed in place of trap seal primers?
- No. Each fixture trap shall have a liquid seal. Section 1007 requires that the traps be protected with a trap seal primer.
  By definition a trap seal primer is “a device and system of piping that maintains a water seal in a remote trap.”
  Devices that do not provide a liquid seal, and rely on a mechanical action are not approved for protection.
Why is a ‘refrigeration machinery room’ required to be separated from other portions of the building?
- This requirement under section 1107.5 of the Uniform Mechanical Code provides for a measure of safety based on the potential level of hazard created by the toxicity or flammability of refrigerants used in the equipment within the machinery room as required by the building code.
In Combination Waste and Vent systems, is it the intent of Section 910.0 or Appendix B, to allow for the installation of more than one (1) p-trap on any branch line that would not exceed fifteen feet (15’) in length? If there is not a prohibition on multiple traps on any one branch is there a limit to the number allowed and or a sizing requirement for proper air flow?
- 1) Yes, multiple traps are allowed on a single branch with the stipulation that all traps and trap arms connected to the branch remain within the 15 ft. limitations from the vented main and a cleanout is installed on each branch per Section 910.6 of the UPC. 2) Nothing in Section 910.0 or Appendix B of the UPC restricts the installation of multiple traps on a single branch as long as all perimeters set forth in the aforementioned code sections have been met.
Can the "enclosed spaces" referred to in UMC Section 609.0 automatic shutoffs be reduced, divided or separated by the introduction of a one-hour fire barrier?
- No. Simply reducing, dividing, or separating a space with a one-hour fire barrier does not eliminate the requirement for an automatic shutoff in an air-moving system. The requirement for the shutoff is to prevent smoke from being spread to a different space other than the space where the smoke originated. If a common system is being used there would still be a potential for the smoke to spread through the supply distribution system, regardless of how the spaces are divided or separated.
UPC Section 905.3 requires each vent to rise vertically 6 inches above the flood level rim of the fixture served. In a back-to-back installation, would the horizontal vent be permitted to be run below the overflow of the bathtub, when the horizontal vent is 6 inches above the overflow of the shower pan?
- No, unless prohibited by structural conditions, a common vent that serves two or more fixtures must rise vertically to a point not less than 6 inches above the flood level rim of the highest fixture served, before offsetting horizontally.
What constitutes altering the system to meet present-day standards?
- The UMC in Sections 104.1 and 104.2 (102.1 and 102.2, 2012)is fairly liberal in allowing existing installations to continue their use under the code in effect at the time of the initial installation. However, Section 104.1 starts by saying that all new work on existing systems, whether it is a repair or alteration, shall comply with this current code. It makes an exception in the second paragraph for "minor" changes; these may be installed according to the code in effect at the time of the original installation. Replacement of ducts or rearrangement of ducts with new hangers, and replacing HVAC equipment of any sort is not ‘minor’. Webster’s Dictionary defines "minor" as "inferior in importance, size or degree; comparatively unimportant." The committee felt that duct work to relocate registers, closing and sealing old duct openings, and repair of equipment that was essentially left in place with the duct work attached constituted "minor" additions, alterations, and repairs. The Authority Having Jurisdiction will of course determine the parameters that define "minor" in its jurisdiction, based on many factors. For example, the Authority Having Jurisdiction may decide that a new code provision, such as automatic shutoff for air-moving systems (UMC Section 609.0 (2003/2006/2009) and 608.0 (2012/2015/2018/2021)), is an important enough life-safety issue that it significantly "raises the bar" on what constitutes a "minor" alteration in the hope to upgrade as many installations as possible.
Are floor sinks required by the UPC to be installed with the flood rim above the finished floor?
- No. The UPC does not require floor sinks to be installed with their flood rims above the finished floor. This has been required by some local Health Departments to prevent the receptors from being used as floor drains and from collecting unsanitary debris or dirt.
1. Does the UMC harmonize its provisions for the clearances for connectors as stated in NFPA 211? We have a Peerless sectional cast iron unit (1,200,000 Btu input), AGA listed for use with a B-vent with draft hood, and noncombustible construction. 2. How do we determine and support which equipment class the boiler should be under?
- 1. Yes, Section 801.1 states that low heat appliances shall be vented in accordance with this chapter and that other gas appliances shall be vented in accordance with NFPA 211 or other applicable standards. 2. Generally, the equipment classification will be supported by the equipment listing. This chapter only covers low-heat appliances (appliances producing combustion gases not in excess of 1,000°F under normal operating conditions, but capable of producing combustion gases of 1,400°F during intermittent forced firing for periods up to one hour).Therefore, the flue gases at the appliance flue outlet will determine if this code shall be used or if NFPA 211 is the correct applicable standard. Your boiler is most likely a low-heat appliance, which would be classified under, “listed equipment with draft hoods and equipment listed for use with Type B vents,” as noted in Table 8-2 (2003/2006/2009)or T802.7.3.4(1)/2012.