Answers and Analysis

No, Section 1001.2 (2003/2006/2009) 1001.1 (2012) permits the use of a common trap for certain like fixtures installed in groupings of two and three. It limits the distance between fixture waste outlets and consequently the lengths of continuous wastes to 30 inches. Where three fixtures drain to a common trap, obviously the maximum spread between the two most distant waste outlets will be twice 30 inches, but the continuous waste pipe from either to a centrally located trap must be within the allowable 30 inches.
In the absence of further instruction in the Code and mindful of basic sanitary limitations on open drain
piping (as short as practicable), the 30 inch waste outlet spread must also be applied to two fixtures sharing
a common trap whether the trap is under one or centered between.

1. No, a tailpiece may be installed in a horizontal or vertical position. However, it must be as short as practicable and not exceed 24 inches in length. 2. The code does not limit the number of offsets. However, each offset represents an increased potential
for stoppages or retarded flow velocity, and unnecessary excessive offsets should be avoided (see
Section 311.5, (2003/2006/2009) 310.5 (2012).
See also 222.0, Tailpiece

Yes, horizontal to horizontal changes of direction within a trap arm are required to be made with fittings as described in Section 405.4 (2003) 404.4 (2006/2009) 419.2 (2012).
See Sections 206.0 and 222.0 (2003/2006/2009/2012), Drainage System and Trap Arm, and Section 1002.3
regarding cleanout requirements for trap arms.

Yes, as requirements for trap and trap arms found in Chapter 10 are separate and independent from stipulations found in Chapter 7 .
See also 706.3

No, the smooth and uniform waterway mentioned in Section 1003.1 prohibits obstructions or other rough edges within the trap that could cause a buildup of soap and grease which could cause a stoppage.
So long as the cleanout does not present obstructions or other rough edges, and the trap is properly
listed, it is acceptable

1. No. Section 1003.3 requires the trap to be the same size as the trap arm to which it is connected. 2. Yes. A 2 inch trap arm and trap installed for a residential kitchen sink is acceptable and is not in violation
of the note under Table 7-3 (2003/2006/2009) Table 702.1 (2012) regarding self-scouring properties.

A trap arm which is larger than its trap, and extending the maximum allowable distance, will place the weir of the trap above the vent opening. The potential for trap siphonage is increased, and trap arm scouring is
decreased.

No. The code requires either a gravity or a hydromechanical interceptor be installed where grease laden waste is present. The code will allow a mixture of the 2 systems or an engineered system where physical
constraints exist and the system is approved by the AHJ. The code does not state a preference for one
system over the other.

1. Sizing of grease traps (Hydromechanical Grease Interceptor) is not based on fixture unit values. Section 1014.4 (2003) and Section 1014.2.2 (2006 and 2009) Section 1014.2.1 (2012) states that sizing is based on the total capacity in gallons (volume) of the fixtures discharging into any grease trap (Hydromechanical Grease Interceptor), which must not exceed 2-1/2 times the certified gpm flow rate of the grease trap. 2. Discharge piping must match or exceed the outlet opening size of the grease trap (Hydromechanical Grease Interceptor). Fixture unit loading imposed upon downstream piping is based on maximum discharge in GPM divided by 7.5 (this represents the standard formula for assigning fixture unit values based on gallonage flow) See Tables 10-2 (2003/2006/2009) Table 1014.2.1 (2012) UPC.

1. A “single service” kitchen utilizes disposable utensils, containers and wrappers intended for a one time use, as well as the disposal of food remnants in a manner similar to that of the “single service” utensils.
2. A warewasher is, by design, smaller than a dishwasher and used for small utensils such as silverware.
A dishwasher could be utilized as a warewasher; however, a warewasher could not be substituted for
a dishwasher.

1. There is no fixture limit imposed by code. In reality, an untrapped, unvented drainage piping system is similar in character and function to an open trough drainage system. An untrapped/unvented pipe
system is effectively a closed trough.
2. Again, there is no limit imposed by code. There is obviously a practical limitation resulting from interceptor
burial depth and the need for adequate pipe flow to prevent settling of sand and other materials
in the pipe due to flow velocities.
3. Standard waste pipe sizing would apply. Oversizing should be avoided. As noted earlier, it is important
that slope, water volume, and pipe area be selected which will assure the greatest degree of scouring
action. Piping which is too flat, or which is oversized, will fail to carry materials such as sand all the
way to the interceptor, thereby creating drainage problems rather than curing them.
In summary, certain waste products must be intercepted or treated prior to entering the sanitary waste
system. A conventional trap and vent system is unsuitable for sand-bearing waste because "self-cleaning"
(Section 1003.1) of a trap is limited by the density of the waste products passing through it. Therefore, a
trough (open or closed) is the best means of assuring that such products will reach the intended interceptor.
Note: All interceptors are required to be vented, whether they have gastight covers or not (Section 1009.4,
2003/2006/2009/2012). The interceptor vent will be located within standard trap arm length based upon the
nominal trap arm diameter.

The term grease trap is no longer used in the UPC. The terms used now are "Gravity Grease Interceptors" and “Hydromechanical Grease Interceptors" The requirements for hydromechanical grease interceptors are found in sections 1014.2 and Table 10-2 (2009), Table 1014.2.1 (2012) and give two ways to size the interceptor using the volume of the fixture 18 X 18 X 12 X 3/231 = 50.5 gallons. Section 1014.2.2 (2009), 1014.2.1 (2012) states that the total capacity in gallons (L) of fixtures discharging into any hydromechanical grease interceptor shall not exceed two and one half(2-1/2) times the certified GPM (L/m) flow rate of the interceptor.
Example: 20 gpm x 2 1/2 = 50. The capacity of the sink is 50.5 therefore the next larger size 25 gpm should be used.
Using Table 10-2, 75% of the fixture volume is used to determine the size.
Example: 50.5 X .75 = 37.8 gallons which would require a 40 gpm Hydromechanical interceptor for one minute drainage and a 20 gpm for two minute drainage.
All hydromechanical grease interceptors are required to have a vented flow control fitting so that the flow rate of the interceptor in not exceeded.
The size of gravity grease interceptors is based on the fixture unit load per Table 7-5 (2009), Table 702.1 (2012) and sized per Table 10-3 (2009), 1014.3.6 (2012).
Example: Up to 8 fixture units = 500 gallons

Per Section 1014.3.6 of the Uniform Plumbing Code, sizing gravity grease interceptors is determined by the total number of fixture units and/or gallons per minute of effluent flowing into the interceptor with a retention time of 30 minutes. Utilizing the sizing found in Table 1014.3.6 will provide the required sizing and retention time.

No. Each fixture trap shall have a liquid seal. Section 1007 requires that the traps be protected with a trap seal primer.
By definition a trap seal primer is “a device and system of piping that maintains a water seal in a remote trap.”
Devices that do not provide a liquid seal, and rely on a mechanical action are not approved for protection.

Section 901.2 of the 2015 UPC dictates that “air circulation shall be ensured throughout all parts of the drainage system by means of vent pipes installed in accordance with the requirements of this chapter and as otherwise required by this code.” Section 1009.4 specifies that “interceptors (clarifiers) shall be so designed that they will not be become air-bound where closed covers are used. Each interceptor (clarifier) shall be properly vented.” Many gravity interceptors are designed with airspace above the center baffle and with the appropriate installation of fittings within the interceptor would ensure air circulation within the drainage system thereby not requiring an additional downstream vent. Gravity grease interceptor configurations, such as those with the center baffle that extends to the lid of the interceptor, would require the installation of a vent downstream to prevent the interceptor from becoming air-bound.

1. No. Per Section 1014.3.6 of the 2015 Uniform Plumbing Code, sizing a gravity grease interceptor is determined using Table 1014.3.6 based on drainage fixture unit values for fixtures found in Table 702.1. Where drainage fixture units (DFUs) are not known, the interceptor is then sized based on the maximum DFUs allowed for the pipe size connected to the inlet of the interceptor per Table 703.2.
2. Footnote 2, in Table 1014.3.6, indicates that a 30 minute retention time has been included in the interceptor volume values found in the table. The sizing of gravity interceptors using Table 1014.3.6, is based on Drainage Fixture Units not load factors.

1. Yes. Per Section 1014.3.4 of the 2015 Uniform Plumbing Code, “each grease interceptor shall be installed and connected that it shall be easily accessible for inspection, cleaning and removal of intercepted grease. A gravity grease interceptor in accordance with IAPMO Z1001, shall not be installed in a building where food is handled. Location of the grease interceptor shall meet the approval of the Authority Having Jurisdiction.”
2. No. Gravity grease interceptors may not be installed in a building where food is handled. Note: The Code does not address the location of hydromechanical grease interceptors, but local health departments may restrict the installation of those units in food prep areas.

1. Research by the National Bureau of Standards (see Recommended Minimum Requirements for Plumbing BH13 (1928) and Self-Siphonage of Fixture Traps BMS 126(1951) was used to formulate Table 1002.2. The testing established acceptable guidelines as to the lengths, both long and short, for trap arms serving plumbing fixtures, including floor mounted water closets.
2. Research done by the National Bureau of Standards, included testing on floor mounted water closets and similar fixtures. The testing established acceptable guidelines as to the lengths, both long and short, for trap arms serving plumbing fixtures, including floor mounted water closets.

The designation of hydromechanical grease interceptors, based on the type of flow control for the unit, changed from A,B,C&D to 1,2,3&4 in the 2015 Uniform Plumbing Code (UPC). Section 301.2 of the 2015 UPC states, “pipe, pipe fittings, traps fixtures, material, and device used in a plumbing system shall be listed (third-party certified) by a listing agency (accredited conformity assessment body) as complying with the approved applicable recognized standards referenced in this code* and shall be free from defects.” Per Section 2.3.1 of ASME A112.14.3, “flow controls and/or vents or air intakes for grease interceptors shall be in accordance with manufacturer’s installation requirements”.

* Section 1014.1 Where it is determined by the Authority Having Jurisdiction that waste pretreatment is required, an approved type of grease interceptor(s) in accordance with ASME A112.14.3, ASME A112.14.4, CSA B481, PDI G-101, or PDI G-102…

ASME A112.14.3-2018 (Hydromechanical Grease Interceptors)
2.3 Flow Controls and/or Vents
2.3.1 The use and placement of flow controls and/or vents or air intakes for grease interceptors shall be in
accordance with the manufacturer’s installation requirements. When a flow control is not required by the manufacturer, testing shall be conducted at the manufacturer’s prescribed rate of flow without any restriction of the flow from the test apparatus to the grease interceptor.

Section 301.2 of the 2015 Uniform Plumbing Code states, “Pipe, pipe fittings, traps, fixtures, material, and devices used in a plumbing system shall be listed or labeled (third-party certified) by a listing agency (accredited conformity assessment body) and shall comply with the approved applicable recognized standards referenced in this code, and shall be free from defects. Unless otherwise provided for in this code, materials, fixtures, or devices used or entering into the construction of plumbing systems, or parts thereof, shall be submitted to the Authority Having Jurisdiction for approval”. Each interceptor must be tested and listed per applicable standards found in Section 1014.1. Unlisted components may not be installed on tested and listed products.

Barrier type trap seal protection devices are not trap seal primers as required in Section 1007.1 of the 2018 Uniform Plumbing Code. There are two types of Code approved trap seal primers per Section 1007.2. Potable water supplied primers that comply with ASSE 1018 and drainage type primers that conform to ASSE 1044. These devices periodically replenish the water to remote or seldom used floor drains and similar fixtures thereby maintaining the code required trap seal depth. Barrier type trap seal protection devices on the other hand, merely slow down the evaporation of water in the fixture trap, thereby maintaining the trap seal for a longer period of time. They do not automatically replenish the water in the trap and would eventually allow the trap to dry up.

Note: IAPMO has listed multiple barrier type trap seal devices that meet the requirements found in ASSE 1072. These devices may be installed on all floor drains and similar fixtures. The listings* for these devices however specifically states that a “trap seal protection device shall not be used in lieu of a trap seal primer”*.
*Identification: Each device shall be permanently and legibly marked with the manufacturer's name or trademark and the application designation (per Table 2 of ASSE 1072-2007). Product shall also bear the UPC® certification mark. Packaging shall bear the manufacturer's name or trademark, model number or description of the device, rating for type of floor, rated for grease-laden waste (if applicable), and the floor drain size.

Characteristics: Barrier type floor drain trap seal protection devices. Trap seal device shall not be used in lieu of a trap primer. Product to be installed with other IAPMO R&T listed fittings, in accordance with the manufacturer's instructions, and the requirements of the latest edition of the Uniform Plumbing Code.
Products listed on this certificate have been tested by an IAPMO R&T recognized laboratory. This recognition has been granted based upon the laboratory's compliance to the applicable requirements of ISO/IEC 17025.

Products are in compliance with the following code(s):

Uniform Plumbing Code (UPC®)
International Plumbing Code (IPC®)

Products are in compliance with the following standard(s):

ASSE 1 072-2007

1. Yes, Per Section 1009.4 of the 2018 Uniform Plumbing Code, “Interceptors shall be so designed that they will not become air-bound where closed covers are used. Each interceptor shall be properly vented”. There are two types of grease interceptors found in the Uniform Plumbing Code; hydromechanical and gravity. Section 1014.2.2, specifically requires a vent on the downstream side of all hydromechanical interceptors. The design of gravity grease interceptors, per Section 1014.3.3, must be constructed to meet the applicable standards found in Table 1701.1 (Referenced Standards). IAPMO Standard Z1001 (Prefabricated Gravity Grease Interceptors), Section 4.6.1 that addresses gravity grease interceptor venting states, “Partitions, baffles, and inlet and outlet devices shall have a venting area not smaller than the cross-sectional area of the inlet or outlet, whichever is greater”. This indicates that the configuration of the piping and baffles within the gravity grease interceptor would dictate if additional venting would be needed to comply with Section 901.2*.
2. See answer 1
3. Yes, as long as all applicable code sections and standards are complied with.
4. No. Per Section 102.1, “In instances where this code, applicable standards, or the manufacturer’s installation instruction conflict, the more stringent provisions shall prevail”.


901.2 Vents Required. Each plumbing fixture trap, except as otherwise provided in this code, shall be protected against siphonage and backpressure, and air circulation shall be ensured throughout all parts of the drainage system by means of vent pipes installed in accordance with the requirements of this chapter and as otherwise required by this code

1. No. Per Section 1017.1 of the 2015 Uniform Plumbing Code, only repair garages and gasoline stations with grease racks or grease pits are required to have oil or flammable liquid interceptors.
2. No. While Section 1017.1 specifically requires an interceptor on all repair garages equipped with grease racks or grease pits, Section 1009.1 enables the Authority Having Jurisdiction the ability to require an interceptor or clarifier on any building where the effluent from the building contains grease, flammable waste, sand, solids or other harmful ingredients.

1. Per Section 1014.3.5 of the 2018 Uniform Plumbing Code, a sample box is a recommendation, not a requirement.
2. Many jurisdictions require a sample box or cleanout downstream of a gravity grease interceptor, which allows testing of the effluent to insure the waste water is within local guidelines for FOG content.
3. The location of the sample box or cleanout, as long as it downstream of the gravity grease interceptor and prior to connections from other sanitary waste piping would be acceptable..

No. The 2012 Uniform Plumbing Code does not specifically required an interceptor for dog hair containment. Section 1009.1, does however give the Authority Having Jurisdiction the power to require pretreatment of waste water if it is deemed harmful to the building drainage system, the public or private sewer, or to public or private sewage disposal.

1. No. Section 1001.2 of the 2015 Uniform Plumbing Code(UPC), specifically states that a “laundry tub” shall be permitted to receive the waste from an adjacent clothes washer. No other fixtures are listed for this use.
2. Section 1001.2 does not permit a floor mounted mop sink to be used in lieu of a laundry tub as a receptacle to receive the waste from a clothes washer. The Authority Having Jurisdiction however, may approve the use of this fixture if it is felt that the installation meets the requirements found in Section 301.3 for Alternate Materials and Methods of Construction Equivalency.

1. Per Section 1017.1 of the 2018 Uniform Plumbing Code, “The separation or vapor compartment shall be vented independently to the outer air. Where two or more separation vapor compartments are used, each shall be vented to the outer air or shall be permitted to connect to a header…”
2. No. Vapor compartment vents on an oil and flammable liquid interceptor are to be separately vented do to the flammable nature of material being vented.

Yes. Per UPC Section 1008.1, a “relieving vent or fresh-air intake” is required to be installed at the “inlet” side of the building trap. A relieving vent or fresh-air intake does not serve the same purpose as a typical plumbing fixture vent which is required to be located at the connection of the trap arm to the waste system drain.

The language found in Section 1014.3.4.2 of the 2012 Uniform Plumbing Code (UPC), was first introduced into the Code in 1982 as part of newly adopted Appendix H - Recommended Procedures for Sizing Commercial Kitchen Grease Interceptors. The proponent of that code change stated the following as the substantiation for that code change; “Without this code change, it would be very difficult to locate the source of oils, fats and grease that are draining into the sanitary drainage system where more than one establishment utilizes the same interceptor.” That language was subsequently moved into the body of the code in the 2006 edition of the UPC.

The code does not expressly state that the trap primer discharge (drain) should be graded to floor drain. Manufacture’s recommend trap primers be installed 12” above finished floor for every 20’ of primer line. It is the committee’s decision that the primer line should be graded to ensure adequate water supply to floor drain.