UNFORM CODES QUESTIONS & ANSWERS

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

Is the removal of a door from a mechanical room in a single family dwelling acceptable in accordance with Section 701.5 of the 2021 UMC, to achieve proper combustion air requirements for combining spaces on the same story?
- No. Simply removing the door is not adequate. The intent of the code is to provide a permanent opening when combining communicating spaces. In addition to removing the door, the casing and door hardware would also need to be removed and the opening should be finished to provide a permanent opening so that the door cannot be readily installed. If the door to the mechanical room is in a bedroom or bathroom the door cannot be removed and combustion air shall be provided from outdoors as required in Section 904.1 of the UMC (2003/2006/2009/2012/2015/2018/2021).
Can a gas shut-off valve be located behind a range or stove, or must it be located in an adjacent cabinet in order for it to be "accessible"?
- Yes. The shut-off valve may be located in, under, or behind the appliance, as long as the appliance can be removed without removing the shut-off valve. Appliance flexible connectors are manufactured to provide for the removal of an appliance (range, dryer, etc.) for access to the shut-off valve.
If the vent connector is required to be "installed within the space or area in which the appliance is located and shall be connected to a chimney or vent" and "connectors shall be short and straight as possible," then that portion of a pipe that leaves the "space or area" of the appliance might be considered a vent and not vent connector, therefore needs to meet vent requirements? If required to be as short as possible, would the length at this vent connector be contrary to that requirement?
- Yes. The code allows a vent connector from a listed gas appliance with a draft hood to pass through walls or partitions if they are Type B or L vents installed according their listings. In addition, single wall metal pipe may be used when installed with a ventilated thimble. The code also allows the horizontal portion of the vent system to equal the vertical height. Note: The UMC limits single-wall penetrations to exterior walls only.
In a commercial building with regularly scheduled restroom mop downs, would the floor drains in those restrooms be considered as having their trap seals adequately protected?
- Regular scheduled mop downs with water may be considered acceptable, provided that adequate water enters the drain and the area is not cleaned with dry chemicals only.
Do I consider fumes from an underground parking garage with a fan-forced exhaust vent as flammable and utilize UMC Section 506.9 for vent termination? Or can you direct me to the correct code section?
- Yes. Garage ventilation systems in Group S, Division 3 parking garages should terminate in accordance with the provisions of Section 506.9.1, since ducts routinely convey exhaust products containing carbon monoxide, smoke, soot, water vapor, and particles of rubber from tires. Because 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.
What constitutes an over-temperature safety protection device? Must the device be a pressure and temperature relief valve or can it be some other type of electrical device?
- An over-temperature safety protection device is installed directly on the water heater by the manufacturer. When the temperature reaches 210°F or higher, this built-in safety device opens and shuts off the fuel supply to the heater. When the temperature falls below 210°F, the built-in safety device closes and allows the fuel supply to flow to the heater. Water heaters that have these devices are labeled to indicate that such a device is included in the water heater design. Standards for the construction of water heaters require this built-in over-temperature device. In addition to this fuel supply cut-off device installed by the manufacturer, the Code requires the additional installation of a temperature and pressure relief valve. Note: This requirement is also applicable to electric water heaters. See also 505.6, 608.0 (2003/2006/2009) 504.6, 608.0 (2012) 505.2 (2015/2018/2021)
Is a spark arrester required on a solid-fuel appliance when it is located under a hood?
- Yes, a spark arrester is required when using solid fuels. The first sentence in Section 517.1.6 of the 2015/2018/2021 Uniform Mechanical Code states that any solid fuel cooking operation requires spark arrestors to protect embers from entering a duct or plenum. The second sentence specifically addresses equipment not located under a hood, and also requires a spark arrestor to minimize embers from passing through a flu or chimney. These two sentences do not contradict one another but compound the requirement for spark arrestors for solid fuel cooking applications whether they are integral to the equipment or not. Please also refer to NFPA 96-14.1.1 and 14.1.7.
Are all direct vent type water heaters constructed with sealed combustion chambers?
- Yes. All properly listed direct vent water heaters are constructed so that all air for combustion is derived directly from the outside atmosphere and all flue gases are discharged directly to the outside atmosphere. Certified or listed direct vent water heaters are required to pass the maximum leakage requirements outlined in the ANSI Standard Z21.10.1 [ANSI Z21.10.1-98 (2003), ANSI Z21.10.1-2004 (2006), CSA Z21.10b-2006 (2009)], as applicable. A water heater is not a direct vent water heater unless it is listed as such and complies with the Code.
Should the termination from a stationary gas power generator be treated as a product conveying duct or as a vent when considering distance to the property line?
- The exhaust pipe for a stationary gas-powered generator is not a product conveying duct and would not be required to adhere to the requirements for termination of a product conveying duct. Additionally, to be classified as a vent, the exhaust pipe must be a listed factory-made vent pipe by definition. Most exhausts for generators are not listed and are manufactured on-site. An exhaust pipe for a generator would most resemble the definition of a chimney per the UMC, but Chapter 8 of the UMC (2003/2006/2009/2012/2015/2018/2021) only covers fuel-burning appliances and refers to NFPA 211 for appliances fueled by fuels other than gas (natural gas). Stationary gas powered generators must be installed per the manufacturer’s installation instructions and NFPA 211, since these appliances do not fall within the scope of the UMC.
Cast Iron horizontal support. Does "Every other joint, unless over 4' then support each joint." Does this somehow mean you cannot butt two fittings together without a pup piece in between to install a hanger for required support?
- Per the UPC, support of horizontal no-hub cast iron pipe and fittings should provide enough bracing to have only minimal weight on the shielded couplings. Support of piping over 4 ft. shall have a hanger on both sides of the shielded coupling within 18 inches of the joint, while shorter sections of pipe and fittings shall be supported at every other joint. The connection between two fittings is considered a joint therefore requiring a hanger on the next joint. Note: The Cast Iron Pipe Institute recommends supporting horizontal cast iron piping by installing hangers on horizontal piping and fittings at sufficiently close intervals to maintain alignment and prevent sagging or grade reversal. Each length of pipe should be supported by an approved hanger located not more than 18 inches from the joint and at each change of direction or alignment with an approved hanger.
What is the intent of the 2021 UMC Section 519.5 regarding the required 10 feet clearance from any wall termination to the property line?
We are able to meet all other clearance requirements of this section with the exception of the 10 feet from any property line. The building is constructed with 0 feet clearance to the property line which faces a public right of way (Public Street).
The tenant's space is on the first floor of a high-rise building with no roof access or pathway to route the exhaust up to the roof. The desired exhaust termination is between 12 feet and 15 feet above the grade level and the building is set back from the street 15 feet, sidewalk is 15 feet wide.
The discharge air velocity is maximum 700 FPM.
The exhaust is treated by a UL listed pollution control unit, prior to discharge out the exterior wall.
The filter efficiency for the PCU is 95% - 98% of particulates removed down to 0.3 microns in size. This is equivalent to a MERV 16 filter and can be considered clean air at the time of discharge.
Our interpretation of this code is that it is intended to protect neighboring buildings from nuisance exhaust discharge.
Would the situation described above be acceptable and in accordance with the intent of the 2021 UMC?
- The purpose of the Uniform Mechanical Code is to “… safeguard life, health, property and public welfare.” The intent of section 519.5 of the 2021 Uniform Mechanical Code is to protect buildings and the public from products of heat, steam, condensation, odors and grease (even if minor).
  
  No. While your project does not appear to comply with the requirements of the 2021 UMC, the Authority Having Jurisdiction would determine if the installation meets the intent of the Uniform Mechanical Code.
How many toilets and lavatories are required, if any, in a retail store that is not located in a mall? Are the owners of the store required to provide public restrooms or just employee restrooms?
- To determine the minimum fixture requirements for a building that will be occupied as a retail store; the occupant load must first be determined. Using section 413.0 (2003), 412.0 (2006/2009) 422.1 (2012) and Table 4-1 (2003/2006/2009) Table 422.1 M-Mercantile (2012/2015/2018/2021) referencing under retail or wholesale store, the fixture counts can be calculated. Section 413.5.1 (2003), 412.5.1 (2006/2009) 422.4 (2012/2015/2018/2021), provides the minimum requirements for customers and employees. Both requirements shall be permitted to be met with a single set of restrooms accessible to both groups. Also refer to 422.3 (2012/2015/2018/2021).