IPC Table 710.1(1)
What it means on the job
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.
Tested in 1 CraftIQ puzzle
- code-checkFixture Unit Calculation for Drain
Related IPC sections
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 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.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.