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Uniform Codes Questions & Answers 

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

Can a listed plastic, backwater valve and a listed plastic, fullway ball valve be installed in a drainage system?

Fullway ball valves are allowed to be installed in a drainage system. A listed plastic, backwater valve or fullway ball valve would be allowed where a plastic drainage system is permitted. See also UPC Section 710.4.

UMC Section 916.1(b) states that the clearance to metal cabinets above a range can be a minimum of 24 inches if a ventilating hood is installed under the cabinet. 1. Does that mean that the clearance to the range hood can be less than 24 inches? 2. Section 916.1(b) #3 states that a listed microwave can be installed over the range if it conforms to the terms of the manufacturers' instructions. Does that mean that the clearance to the bottom of the microwave must be a minimum of 24 inches? 3. If the manufacturers' instructions allow the microwave to have less than a minimum of 24 inches clearance above the range, is that permissible?

1. No, Section 916.1(B), #2 (916.1.2#2/2012) would require a minimum 24 inches clearance between the cooking surface and the bottom of the hood if the hood meets the requirements of Section 916.1(B), #2. 2. No. The clearance can be less if it is installed per the microwave manufacturer’s listed minimum clearances. 3. Yes

May the pressure drop through the meter, valves, and backflow device be used when determining the need for a pressure regulator?

Water pressure regulators are usually installed in the building supply of the building to regulate the water pressure to the building, leaving the higher pressure to the outside yard piping. Section 608.2 requires a pressure regulator to be installed when the main pressure exceeds 80 psi. However, any devices or elevation changes which influence the static pressure may be considered when determining the need for a pressure regulator. If the static pressure in the street main varies, then the basis for the installation of the pressure regulator is determined from the high pressure, but the piping design is based on the low pressure.

I am working in a project in Davis, CA where a restaurant with cooking appliances will be installed in the first floor of a 4-story building. The exhaust hood (type 1) installed above the cooking appliances is connected to a Pollution Control Unit (PCU), which will remove grease, vapors, smoke, etc from the airstream before discharging it to the outside. The building has no shaft and I am proposing to discharge the air from the PCU through the side wall. My question is, From California Mechanical Code (CMC) perspective ……. is the air coming from the PCU and discharged to the outdoor considered to be “environmental air”? Comment As part of the permit approval process, the Fire Dept in Davis, CA is asking me to provide them with a definition of “environmental air” but I could not find it in the 2010 CMC. They want to know “hard” numbers such as maximum concentration (in %) of pollutants allowed in an airstream in order to be considered “environmental”. I checked unsuccessfully many Internet sites and then decided to ask for your help in finding such definition. CMC only defines “environmental air duct” but it is not enough for Davis Fire Dept. Can you please provide such definition or let me know where I can find it?

No. The exhaust air being discharged from the pollution control unit to the outside through a side wall termination is still considered as grease-laden cooking vapor and shall be installed as per Section 510.8.3. The UMC states that only a domestic range vent would be considered environmental air. The definition of Environmental Air Duct as defined in Chapter 5 Section 502.0 would be used to define environmental air. Pollution Control Units are generally listed to UL1978 and considered part of the exhaust duct system and not the exhaust termination.

Is an approved double check valve assembly required on the potable water supply line to a “dry automatic fire sprinkler system” when the system is charged by air or nitrogen?

If this is a completely separate fire sprinkler system, then a detector check valve is usually the only crossconnection control device that is required to protect the public water main. However, if the fire protection system is supplied by the potable water supply (combination main), then a listed double check valve assembly would be required to be installed to protect the potable water supply per Section 603.0. Contamination of the potable system could occur from the Fire Department connection. When chemical corrosion inhibitors and anti-freeze solutions other than water solutions of pure glycerine or propylene glycol are used, a listed reduced pressure principal backflow preventer is required to be installed.

Is a Type B gas vent equal to an insulated type connector?

Yes. A Type B vent is an insulated connector. The code states in part, that a portion of the connector shall be listed Type B or Type L vent material or be provided with equivalent means of insulation. This means equivalent to the thermal resistance of those vent systems.

Does UPC Section 405.2 (2003) 404.2, 2006/2009) 402.11 (2012)402.10 (2015) require a 1 foot by 1 foot tub access opening when solvent cemented joints are used?

No. Section 405.2 (2003) 404.2, (2006/2009) 402.11 (2012) 402.10 (2015) requires access panels or utility space of at least 12 inches in its least dimension for fixtures having concealed slip joint connections. Solvent cemented plastic pipe joints are not slip joint connections. See also 221.0, Slip joint (2003/2006/2009/2012)

Per UMC Section 403.7 Exhaust Ventilation "Exhaust airflow shall be provided in accordance with the requirements in Table 4-4. Exhaust makeup air shall be permitted to be any combination of outdoor air, recirculated air, and transfer air." Per Table 4-4, Parking garages are to be exhausted at a rate of 0.75 cfm/ft2. Can parking garage exhaust rate be modulated below the listed 0.75 cfm/ft2, if a CO monitoring system is installed in the parking garage?

No, systems for removal of vapors, gases, and smoke shall be designed by the constant velocity or equal friction methods prescribed by Section 505.2 (2006/2009/2012) of the code. The Authority Having Jurisdiction may approve a design that incorporates a variable system if it is determined by the AHJ to be equivalent to the code.

Does UPC Section 416.0 (2003) 415.0 (2006/2009) 417.5 (2012/2015) require the hot water supply piping to be on the left side of the fixtures, or does this section apply solely to the required placement of the hot water control valve?

Section 416.0 (2003) 415.0 (2006/2009) 417.5 (2012/2015) requires that the hot water be connected to the left side of the faucet or diverter; there is no orientation requirement for piping, existing walls, floors, or ceilings.

1. Regarding the interlocking of electrical equipment to the dust collection system, a tenant states that only his sanding equipment generates “dust”, therefore, are the only machines that need to be interlocked with the dust collection system. Does this meet the provisions of Section 503.1? 2. He further claims that some of his equipment, table saws and related equipment do not generate airborne dust but rather they produce chips and small fragments of wood not regulated by Section 503.1. Is this assumption correct? 3. Would a piece of equipment such as a planer, which produces combustible shavings or “curls” of wood still require the interlock with dust collection equipment?

1. Section 503.1 - All equipment that produces dust must be interlocked. 2. Section 505.1 - The building or fire code determines when ventilation equipment is required. 3. Section 503.1 - Yes. A planer is considered dust-producing equipment.

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