International Plumbing Code

IPC 1002.2

S-traps are prohibited by code because they are prone to self-siphoning, which breaks the trap seal and allows sewer gases into the living space. A P-trap must be used instead.

IPC 1002.3

S-traps are prohibited by IPC 1002.3 (Prohibited traps, item 5) and virtually all modern plumbing codes. S-traps are prone to self-siphoning: as water flows down the vertical leg after the trap, it can create enough suction to pull the water seal out of the trap, allowing sewer gases to enter the living space. A P-trap with proper venting must be used instead.

IPC 1003.3.4

A sampling tee or port must be installed on the outlet (downstream) side of the interceptor to allow the municipality or authority to test effluent quality. This is required by most jurisdictions and sewer use ordinances.

IPC 1003.3.5

Garbage disposals (food waste disposers) are generally prohibited from discharging through a grease interceptor. The ground food particles overwhelm the interceptor's capacity and require much more frequent cleaning, reducing effectiveness.

IPC 312.10 / ASSE 5110

Test cocks on backflow preventers must remain accessible for annual field testing by a certified tester. Obstructing or burying test cocks prevents required testing and is a violation of the water purveyor's cross-connection control program.

IPC 424.3 / ASSE 1016

All shower and tub/shower combination valves must be pressure-balancing, thermostatic-mixing, or combination type to prevent scalding. This is a life-safety requirement, especially for children and elderly.

IPC 424.5

Hot water must be connected to the left side of the valve (when facing the valve from inside the shower). This is a universal plumbing convention and code requirement to prevent scalding confusion.

IPC 501.1 / IFGC 305.3

Gas-fired water heaters in garages must have their ignition source elevated a minimum of 18 inches above the garage floor to prevent ignition of flammable vapors from gasoline and other fuels.

IPC 504.6

This installation has three serious code violations. First, the discharge pipe is 1/2 inch but the T&P valve outlet is 3/4 inch — the discharge pipe must never be smaller than the valve outlet size. Reducing the pipe restricts emergency relief flow and can cause dangerous pressure buildup. Second, CPVC is not rated for the 210 degrees F discharge temperature of a T&P valve — the pipe can soften and fail at the exact moment it is needed most. Third, no valve of any kind (ball valve, gate valve, or check valve) is permitted in the T&P discharge line. A closed valve prevents emergency pressure relief and can result in a catastrophic tank explosion. This is a life-safety issue that every UA apprentice must recognize immediately.

IPC 504.6.2

The T&P relief valve discharge pipe must not be smaller than the valve outlet, which is 3/4". Reducing the pipe restricts the relief flow and creates a dangerous pressure condition.

IPC 604.3 / IPC Table E103.3(2)

Add it up per IPC Appendix E: three full baths (~3.6 WSFU each), kitchen sink + dishwasher (~2.5), laundry (~1.4), and two hose bibbs (2.5 each) put the building in the 18-22 WSFU range. From Table E103.3(2) at 46-60 PSI, a 3/4-inch meter-and-main is good for roughly 10-14 WSFU at typical development lengths — this load wants a 1-inch service. The 15 feet of elevation also costs 6.5 PSI (0.433 PSI/ft) before friction. Undersized services show up as pressure crashes when two fixtures run at once.

IPC 604.8 / ASME A112.26

A single PRV with no bypass means the entire residential zone loses water every time the valve is serviced. The IPC doesn't mandate duplex stations — this is a project-specification and high-rise best-practice requirement: two PRVs in parallel with isolation valves so one can be rebuilt while the other carries the zone. Know the difference between what code requires and what the spec you bid requires — both get you red-tagged on this job.

IPC 604.8 / Manufacturer installation requirements

IPC Section 604.8 and manufacturer requirements mandate a strainer upstream of every PRV to prevent debris from fouling the valve seat. Without a strainer, particulate in the water supply causes the PRV to fail — either stuck open (allowing dangerously high pressure downstream) or stuck closed (cutting off water supply to the zone).

IPC 605.11.2

Lead solder is prohibited on any pipe or fitting in a potable water system. Only lead-free solder (0.2% maximum lead content) may be used per the Safe Drinking Water Act and plumbing codes.

IPC 605.24

Dissimilar metals (steel valve body to copper pipe) must be joined with a dielectric fitting to prevent galvanic corrosion.

IPC 607.3 (thermal expansion control) / project specification

Don't misread the code here. IPC 604.8 only governs WHEN a pressure-reducing valve is required (static pressure over 80 psi) plus its setting/bypass rules — it does NOT mandate a relief valve downstream of each PRV. The actual code requirement is thermal-expansion control on the closed system per IPC 607.3, which is normally satisfied by an expansion tank at the water heater/closed zone, not a relief valve at every PRV. A downstream relief valve at a high-rise PRV station is still good practice / spec: if the PRV fails open, piping and fixtures rated for 80 psi could see 150+ psi. Know what code mandates (expansion control, IPC 607.3) versus what the spec adds (PRV-failure relief).

IPC 607.3.2

When a backflow preventer or check valve is installed on the water service (creating a closed system), a thermal expansion tank is required. Without it, heated water expanding has nowhere to go and can cause dangerous pressure buildup.

IPC 608.1

A garden hose submerged in a pool creates a direct cross-connection. If a back-siphonage event occurs, contaminated pool water can be drawn into the potable supply. Hose bibbs must have vacuum breakers and hoses must never be submerged.

IPC 608.15.1

Faucets and fill valves must maintain an air gap of at least 1 inch or two pipe diameters (whichever is greater) above the flood-level rim of the fixture. A spout that can be submerged creates a backflow risk.

IPC 608.15.4.2

This is a cross-connection violation. A hose connection that can be submerged below the flood-level rim creates a backflow hazard. The dirty mop water in the sink could be siphoned back into the potable water supply during a back-siphonage event. A listed atmospheric vacuum breaker (ASSE 1001) or hose connection vacuum breaker (ASSE 1011) must be installed on the hose bibb.

IPC 608.16.4 / ASSE 5013

The relief port discharge must terminate with an air gap above any drain receptor. Without an air gap, a cross-connection is created at the very device meant to prevent cross-connections. The discharge must also be visible to indicate when the relief valve is operating.

IPC 704.1

For pipes 3 inches and larger, the minimum slope is 1/8 inch per foot. A slope of 1/4 inch per foot exceeds the minimum and is acceptable. While the minimum would suffice, a steeper slope within reason provides better flow velocity and self-scouring action.

IPC 705.5

ABS and PVC cannot be joined with solvent cement. These dissimilar plastics require a listed mechanical coupling (such as a banded no-hub coupling) or approved transition fitting.

IPC 706.3

Sanitary tees may only be used for vertical-to-horizontal transitions. For horizontal-to-horizontal connections, a wye with 45-degree bend or combination wye-bend must be used to maintain proper flow.

IPC 708.3

This cleanout layout meets IPC requirements. Cleanouts are required at the base of stacks, at each aggregate change of direction greater than 135 degrees (45 degrees from straight), and at maximum 100-foot intervals for 4-inch and larger drains (75 feet for smaller drains). The installation is compliant.

IPC 802.1

This installation is correct. Ice machines, food-handling equipment, and similar appliances must discharge through an indirect waste connection to prevent sewage backflow from contaminating food or ice. The 2-inch air gap exceeds the minimum requirement (1 inch or two times the pipe diameter, whichever is greater) and ensures a physical break between the fixture drain and the sanitary system. This is one of the first cross-connection control lessons taught at the UA hall — if it makes food or ice, it gets an air gap.

IPC 905.2

The vent connection must be above the trap weir (the overflow point of the trap). Connecting below the weir makes it a wet vent carrying waste, not a true vent, and will not properly protect the trap seal.

IPC 905.5

Vent pipes must rise vertically to a point at least 6 inches above the flood-level rim of the highest fixture served before turning horizontal. This prevents waste from backing up into the vent.

IPC 906.2

Crown venting (connecting the vent at the top of the trap) is prohibited because it creates a cross-connection path and can siphon waste into the vent. The vent must connect to the trap arm downstream of the trap.

IPC 909.1 / Table 909.1

For a 1-1/2" trap arm, the maximum distance to the vent is 6 feet per IPC Table 909.1 (Distance of Trap From Vent, Section 909). At exactly 6 feet, this installation is at the maximum but still within code. The slope of 1/4" per foot is the minimum required for pipes smaller than 3 inches. The critical concern is that the pipe fall over 6 feet (1.5 inches total) does not drop the trap arm below the trap weir level.

IPC 912

Wet venting is permitted by IPC Section 912 (Wet Venting) when properly configured. The wet vent must be at least 2 inches and serve as both drain and vent for bathroom group fixtures. The dry vent portion must connect at or above the highest fixture drain, and the wet vent receives fixtures in a top-to-bottom arrangement. This bathroom group configuration is a common and compliant wet vent layout.

IPC 917

AAVs are permitted by the IPC when a conventional vent is not feasible, provided: the AAV is listed (ASSE 1051), installed at least 4 inches above the fixture drain, within the maximum developed length of the trap arm, accessible for service, and the building has at least one conventional vent stack open to atmosphere. This installation meets all requirements.

IPC Section 604.8

This passes code. IPC Section 604.8 requires that water pressure at any fixture not exceed 80 psi. The system design maintains maximum 75 psi at the lowest fixture in each zone, which is within the 80 psi limit. The lowest zone (floors 1-12) at 65 psi from city main pressure does not need a PRV since it already falls below 80 psi at all fixtures. The three upper zones each have PRV stations that reduce the booster pump output pressure to appropriate zone pressures. This is a well-designed high-rise plumbing system that properly addresses the 0.433 psi per foot of elevation head that makes pressure management essential in tall buildings.

IPC Section 803.2 / FDA GRAS Classification

Propylene glycol is classified by the FDA as 'generally recognized as safe' (GRAS) and is non-toxic, unlike ethylene glycol which is hazardous to humans and animals. The IPC permits discharge of non-toxic substances to the sanitary drain system. Propylene glycol solutions at typical concentrations used in HVAC systems (25-50%) are biodegradable and do not pose a toxicity hazard to municipal wastewater treatment processes. However, contractors should always verify local sewer use ordinances, as some jurisdictions impose biochemical oxygen demand (BOD) limits that may require dilution or metered discharge of large volumes. For most routine system flushes of this volume, sanitary drain disposal of propylene glycol is code-compliant.

IPC Table 709.1

Kitchen sinks require a minimum 1-1/2" drain. The 1-1/4" size is only permitted for lavatory (bathroom) sinks. An undersized kitchen drain will clog frequently from food waste.

IPC Table 710.1(1)

Per IPC Table 710.1(1), a 3-inch horizontal building drain at 1/8" per foot slope can handle up to 36 drainage fixture units (DFU) (42 DFU is the capacity at the steeper 1/4" per foot slope). With only 12 DFU on this line, it is well within the capacity of the 3-inch pipe. The critical factor is that no single branch carries more than its rated capacity, and no more than two water closets discharge into a 3-inch horizontal branch. This installation is compliant.

IPC Table 906.1

For a 1-1/4" trap arm, the maximum distance to the vent is 5 feet. Exceeding this distance risks siphoning the trap seal. The trap arm distance is measured from the trap weir to the vent connection.

IPC Table 906.1 / IPC 906.2

A 1-1/4" vent is the minimum size for an individual vent serving a lavatory with a 1-1/4" trap. The vent size must be at least one-half the diameter of the drain it serves, with a minimum of 1-1/4". This installation meets the requirement.