UNFORM CODES QUESTIONS & ANSWERS

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

Are domestic clothes dryers allowed to terminate vertically through the roof to a “tee top” flashing without a back-draft damper?
- No. Sections 504.3.1 and 504.1 (2003/2006/2009/2012), 504.4 (2015/2018) of the UMC both state that exhaust ducts shall be equipped with back-draft dampers.
What is the required vent size under the sink (not the foot vent)?
- Per Section 909.1 of the 2015 and 2018 UPC, pipe sizing for island drains “shall be as elsewhere in this code”. Sizing requirements for drainage and vent piping may be found in Tables 702.1 and 703.2. A domestic kitchen sink drain has an assigned drainage fixture unit value of two, requiring a minimum 2” waste line and 1-1/2” vent.
  Note: The 2015 Illustrated Training Manual, Figure 909.1B shows a code compliant drawing of an island sink installation.
1. When two type 1 hoods are joined end to end over a long cook line, is it required in the UMC the seam created between the ends of two adjoining hood tops be sealed to prevent the accumulation of greases up and on top of the hood where no suppression systems exist? 2. Is there a specific material used to make the seal?
- 1. Yes, all seams, joints, and penetrations of a hood enclosure where grease vapors could accumulate shall be sealed. Although the joint between the two hoods is not within the enclosure, the joint provides a place where grease vapors could accumulate and must be sealed. Section 508.7 of the 2015 Uniform Mechanical Code states that Seams, joints, and penetrations of the hood enclosure that direct and capture grease-laden vapors and exhaust gases shall have a liquid-tight continuous external weld to the hood’s lower outermost perimeter.
  2. No specific material is recommended but any material/product used must meet the definition of liquid-tight in Chapter 2 of the UMC as “… not to permit the passage of liquid at any temperature.” Guidance can also be found within Annex A of NFPA 96 which defines a continuous weld as: Welding is a fabrication technique for joining metals by heating the materials to the point that they melt and flow to form an uninterrupted surface of no less strength than the original materials.
I have a 23 story building with a 2' wide canopy that runs along the entire length of the building at 1st floor ceiling height. The canopy itself is only 304 sq/ft total. The vertical outside wall above the canopy is 259' high by 152' wide, which equals 39,368 sq ft. Do I figure 50% of the vertical wall surface or less? What tables should be used for determining the size of canopy drains?
- The calculation for a single side wall would be 50% of the total square footage area. This would be added to the roof square footage area, or “canopy” square footage area for which the rain from the wall would collect and be drained away. Using Table 11-2 (2009), 1101.11(2012), 1101.12 (2015), 1103.2 (2018), 1103.1 (2018), use the column of rainfall rate for their area (see Appendix D), then follow down the column that is equal to or exceeds the calculated square footage area. Next, follow to the left column to determine the roof drain and vertical piping sizing. The size of the horizontal drain should be determined by Table 11-2 (2009), 1101.7 (2012), 1101.8 (2015), 1103.2 (2018).
In the UMC: 1. Would a building having an air-moving system in excess of 2,000 cubic feet per minute with no enclosed spaces require an automatic shutoff? 2. What is considered an enclosed space?
- 1. No, as long as the exits are direct and do not exceed 100 feet. 2. Enclosed is defined as, "surrounded." Enclosed space would, therefore, include occupied rooms that do not have direct access to the exterior. This would also apply to interior rooms that only exit into the hallway.
Are trap primers required for floor sinks: 1. Under a sink located in a meat cutting area of a small general store? 2. Located outside a freezer box for a drain for condensate from the freezer? 3. Under a long chest-type, frozen food container or a chest-type cooler for cheese and deli products?
- 1. Each jurisdiction has the option of how to enforce Section 1007.0. Trap primers are usually not required if the plumbing fixture in question receives an adequate supply of water to maintain the trap seal. 2. A floor sink that receives condensate discharge normally would not require a trap primer if the condensate flow is continuous year round. 3. See answer for #2.
Is a UL listed tape required to seal ducts?
- Yes. Section 602.4 of the UMC states that "duct joints shall be made substantially airtight by means of tapes, mastics, gasketing, or other means." Closure systems for rigid air ducts and plenums shall be listed in accordance with UL 181A, Standard for Closure Systems for Use with Rigid Air Ducts and Air Connectors. Flexible air ducts shall be listed in accordance with UL 181B, Standard for Closure Systems for Use with Flexible Air Ducts and Air Connectors. (See Chapter 17, Part II.)
Can soft annealed copper which is enclosed in a wall cavity or above a ceiling be considered to be in a raceway?
- No, a wall cavity or ceiling in a building is not considered a raceway. Walls and ceilings are always subject to cutting or penetrating in some shape or form. A raceway is an enclosed channel designed expressly for holding the annealed copper.
How many total hangers would be required on a 100' straight run of 10' lengths of No Hub Cast Iron pipe?
- Per Table 313.3 of the 2018 Uniform Plumbing Code, Hubless Cast Iron, installed horizontally, shall be supported at every other joint unless over 4 feet, at which point it has to be supported at each joint. Additional requirements referenced in the footnotes include: 1) the adjacent joint must be supported within 18 inches of the joint; 2) a brace must be installed at least every 40ft. to prevent horizontal movement of the pipe; 3) a support must be installed at each horizontal branch connection and; 4) hangers may not be placed on the coupling.
  
  A no-hub coupling, much like a threaded iron pipe coupling, consists of two joints. One half of the coupling creates a water tight seal for one piece of pipe or fitting while the other half serves a similar function for the connecting pipe or fitting. Per Table 313.3, a hanger for hubless cast iron needs to be installed within 18 inches of the joint. Since a no-hub coupling consists of two joints, a hanger would be required on both sides of the coupling.
Does section UMC 510.1.3 Duct Installation, regarding sloping of exhaust ducts with "not less than 2 percent slope on horizontal runs up to 75 feet and not less than 8 percent slope on horizontal runs more than 75 feet", pertain only to the sloping of Type 1 grease exhaust ducts only, like it had in the previous edition of the code?
- No, Section 510.1.3 of the 2018 Uniform Mechanical Code does not pertain to Type 2 ducts. Section 510.1.7 of the 2018 UMC pertains to Type 2 duct systems. Type 2 exhaust duct used with a moisture related process such as a dishwasher would be required to drain back to the hood.