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Uniform Codes Questions & Answers 

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

By referencing UMC Section 802.5.3(3) or 802.5.5.3 (2012), for sizing two draft hood equipped appliances, is it allowed to put unlimited pipe and elbows both horizontal and vertical in the system?

No. The length of horizontal runs and changes in direction for a Category I venting system are limited per Sections 803.2.4 and 803.2.6.

Can a floor drain be used as an indirect waste receptor?

The UPC defines a receptor as an approved plumbing fixture of such material, shape, and capacity as to adequately receive the discharge from indirect waste pipes, so constructed and located as to be readily cleaned. Section 804.1 further requires that receptors be approved for the use proposed and be designed to prevent splashing or flooding, and be located where readily accessible for inspection and cleaning. Floor drains are not defined. However, Section 412.1 (2003) 411.1 (2006/2009) 418.2 (2012/2015) states that a floor drain shall be considered a plumbing fixture and shall be provided with a strainer and be suitably flanged to provide a water-tight joint in the floor. The Code does not eliminate the use of an approved fixture that could be used both as a receptor and a floor drain, providing it meets all the criteria of both. This has led to the development of a combination funnel type floor drain, which is shown in various drainage speciality catalogs. It provides a raised funnel shaped receptor which is located in the center of the floor drain strainer. If a funnel drain is of such shape and capacity as to prevent splashing or flooding and located where readily accessible for inspection and cleaning, it may be acceptable as a receptor. If it is provided with an adequate strainer around the periphery, it could also serve as a floor drain and would in effect be of dual purpose. While an unmodified floor drain cannot be used as an indirect waste receptor, a suitable indirect waste receptor could be used as a floor drain.

When installing listed FAU equipment, must you follow the manufacturer’s specs if the specs are more restrictive?

Yes, the manufacturer’s specifications should be followed to comply fully with the UMC. UMC Section 103.0 points out that whenever there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable. It also states that the most restrictive requirement shall govern. The UMC Section 304.1 (2003/2006/2009) and 303.3 (2012) points out that installation of appliances “shall conform to the conditions of listing.” The manufacturer’s specifications and installation instructions are provided to enable the installer to comply with the listing of the appliance.

UPC Section 704.2 allows two fixtures to be set back-to-back, or side-by-side, provided that each fixture waste separately into an approved double fitting having inlet openings at the same level. Would a double sanitary tapped tee or a double sanitary tee, if sized correctly, be approved for this use? Would two kitchen sinks set back-to-back with a 3 inch x 11/2 inch double sanitary tapped tee be approved? Would two showers set back-to-back with a 3 inch x 2 inch double sanitary tee be approved?

Section 704.2 allows fixtures which are set back-to-back to waste separately into “an approved double fixture fitting.” The appropriate fitting for back-to-back trap arms would be a double inlet fitting which is configured to create a directional flow toward its 60 degree branch inlets at the barrel connection. A sanitary cross is unacceptable as a fixture fitting which is why the increased size option allowed by Section 706.2 is not included in Section 704.2.

We have 3 ventilation fans on a sloped roof (4?12). They are accessible for yearly service only from the room. This equipment is for ventilation only; it’s in an uncooled pool room with multiple garage door type openings for summer comfort. Fans were installed for constant exhaust of pool chlorine vapors and to create summertime air movement for swimmers. There are no maintenance platforms. Since the fans are not refrigeration and only serve to ventilate, are the maintenance platforms required?

No, the maintenance platforms are not required. Since the fans are used to ventilate the pool chlorine vapors, the installation would be considered a product conveying system per Section 502.0. Section 503.1 states “Motors and fans shall be accessible for servicing and maintenance.” There is no mention that a platform is required, only that they be accessible. Section 305.0 refers to access for appliances. A ventilation fan does not meet the definition of an appliance in Section 203.0 (2003/2006/2009/2012); therefore a working platform is not required.

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..

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