IPC Table 906.1

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 / 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.