Appeal 33456

Section C 601 of the 2021 Oregon Plumbing Specialty Code

Emergency/Overflow floor drain fixture drains into intermediary drainage stack with individual vent. See attached Exhibit 1 with ‘Standard Approach’ configuration for more detail.

Emergency/Overflow floor drain fixture drains directly into primary drainage stack. See attached Exhibit 1 with ‘Proposed Approach’ configuration for more detail.

The owner has requested an overflow floor drain added at residential dwelling unit kitchens to capture overflow from the kitchen sink and/or dishwasher. Because the emergency floor drain does not add to the drainage stack load, there is not a concern about overloading the capacity of the stack. The function of the individual vent provided in the standard approach (See exhibit, Left Figure) is to protect the fixture against siphonage (self-siphonage and to some extent, induced siphonage). The stack allows for airflow to balance pressure differentials within the system to ensure no more than 1 inch water seal is depleted even under a maximum loading event.
The viability of this approach and performance can be verified by reviewing the performance of the single stack drainage configuration, which allows fixtures to connect into the stack directly. The proposed configuration, however, is not a single stack drainage configuration, given that the proposed configuration has the sink individually vented as well as the drainage stack. Given the research undertaken on the airflow performance and assurance of trap seal protection during a peak drainage flow event, there are no concerns regarding the performance of the proposed approach.
Attached is a study from Heriot Watt University commissioned by ASPE Portland (Exhibit 2) as well as a paper authored by the proponent reviewing the details of design requirements for the single stack drainage configuration in 12 different regions (Exhibit 3).

Responding to owner requests regarding water damage from residents leaving sinks running and clogging the overflows, there has been an increasing number of requests to provide floor drains in bathrooms and/or kitchens. The cost of providing an additional drainage stack is often seen by the developer as not financially viable in many cases.
Additionally, requirements for firestopping at floor penetrations and concealed piping materials in Type IV-B construction add cost and installation complexity to reduce fire risk.
This solution makes the additional floor drain viable, while reducing costs, fire risk, and the potential for water damage, all while relying on proven drainage theory and international design guidance.