Every week we will be including additional questions and informal UPC and UMC interpretations
- Is it permissible for an atmospheric vacuum breaker to be located within a laboratory fume hood?
- No. Section 603.4.15 (2003) 603.4.14 (2006/2009) 603.5.13 (2012) 603.4.9 (2015, 2018, 2021) specifically prohibits the location of backflow preventers in any area “containing fumes that are toxic, poisonous or corrosive.” A backflow preventer that opens to atmosphere is especially unacceptable because there is a possibility of drawing contaminated vapors into the water piping system through the air intake.
- Is there an exception for small quantities of non-A1 refrigerants, so that a refrigeration machinery room is not required?
- No, there is no exception for small quantities.
- When using horizontal wet venting:
1. May the fixture branch serving a water closet discharge “straight through” the inlet (not the wye branch) of the wye fitting?
2. Must the fixture branch for a water closet come off the wye branch of the fitting?
Comment: I being told it can be either way.
- Fittings for horizontally wet vented drainage systems are not required to be “taken off above the drainage centerline” as required for individually vented horizontal fixtures as found in Section 905.2 of the 2021 UPC. Without that requirement, the fixture may be connected to the run (straight through) or branch of the fitting.
- Right and left couplings were installed for the fuel gas line, located in the crawl space. 1. Is the couplings location in the crawl space allowed by the UMC for service accessibility? 2. Is crawl space considered as a concealed space per Section 1311.3?
- 1. Yes. 2. No. A crawl space is considered to be accessible, unless it meets the definition of concealed which is to hide or cover up. Most crawl spaces meet the definition of accessible, but there may be a case where the crawl space is not large enough for adequate access and is considered not accessible which could then be defined as a concealed space.
- 1. Is the Dishwasher Air Gap fitting required to protect the public water supply?
2. Is the Dishwasher Air Gap fitting required to assure no possibility of a grey-water siphon from the p-trap into the dishwasher?
3. Is the Dishwasher Air Gap fitting required to prevent black-water sewage from entering a dishwasher?
- 1. No. Section 414.1 of the 2021 Uniform Plumbing Code requires domestic or commercial dishwashing machines to comply with UL 749. Domestic dishwashers are to be tested and listed to NSF 3 and UL 921, which requires compliance with ASSE 1006. Section 1.3.4 of ASSE 1006 states, “Potable water supplies to the unit shall be protected against contamination by means of air gaps or other acceptable devices. This requirement applies to the supplying of potable water to all accessories such as dispensers and injectors as well as the washing machine.” Dishwashers not listed to UL 749 and ASSE 1006 must be approved by the Authority Having Jurisdiction prior to installation as prescribed in Chapter 3. The drainage air gap fitting described in Section 807.4, is intended to prevent backflow of waste water from the kitchen sink into the washing compartment of the dishwasher in the event of a stoppage in the kitchen sink or waste line.
2. Kitchen sink waste is not gray water* but would be considered sewage**. The drainage air gap fitting for a residential dishwasher is intended to prevent backflow of waste water from the kitchen sink into the washing compartment of the dishwasher, in the event of a stoppage in the kitchen sink or waste line.
3. Yes. See #2
- Can a factory-made air duct be used to supply the first and second floor only; and a separate independent factory-made air duct be used to supply the third floor only?
- No, under section 603.3 of the 2012 Uniform Mechanical Code factory made air ducts shall not be used as vertical risers in structures greater than two stories.
- Is a shower without a threshold required to have a test such as ADA showers? Is a temporary dam to fill the receptor for test in accordance with the UPC?
- The code does not separate the testing of an ADA shower installation and a typical shower with a curb or threshold. If constructed correctly, even an ADA compliant “roll-in shower” would have a high point at the entrance of the shower enclosure. All areas of this “enclosure” would be have to be verified as “water-tight” as required by the code.
- Do you need a 1 inch clearance from combustible materials for a single dwelling domestic kitchen range exhaust duct and a domestic type clothes dryer exhaust duct?
- No. Domestic range vents and domestic dryer vents do not require a minimum clearance to combustibles unless specifically required by the manufacturer’s installation instructions. It should be noted that there is a 1 inch minimum clearance requirement between an exhaust duct and shaft serving a cooking appliance equipped with an open-top broiler per Section 920.0 (2003/2006/2009/2012/2015.2018/2021).
- This is a request for an interpretation relating to the adaptation of a sanitizing unit to a urinal/toilet flushometer valve tailpiece. 1. May devices of this type be installed on the flushometer tailpiece? 2. Since the Code requires a vertical separation of 6 inches from the critical level of the flushometer valve to the fixture, would this also apply to a sanitizing unit?
- 1. Yes. Devices of this type which depend on water flow in the vertical tailpiece to aspirate the sanitizing material into the water stream (no pumps or other method of pressure injection present), when properly installed, should not constitute a cross-connection. Proper installation includes a vacuum breaker on the pipe downstream of the flushometer valve, but ahead of the sanitizer connection. 2. Yes. The vacuum breaker for a flushometer is tested to comply with American National Standards Institute ASSE 1001 (atmospheric type vacuum breakers) and approval under this standard requires that the entire valve or its established critical level be installed at least 6 inches above a fixture or source of contamination with no possibility of the device being subjected to any back pressure. Although Section 603.4.1 (2003/2006/2009), 603.5.1 (2012/2015/2018/2021) requires that the critical level of a flushometer valve vacuum breaker on a water closet or urinal be at least 6 inches above the fixture, when a device such as a sanitizing unit is added, the 6 inch minimum from the critical level to the point of the sanitizer discharger must be maintained.
- Can combustion air for a vented wall furnace be supplied from inside a new single-family structure which is built to meet unusually tight construction requirements?
- Yes, only if the combustion air provisions of Section 701.1 (2003/2006/2009/2012/2015/2018/2021) are met.
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