Residential Building Inspector B1Footings and FoundationsEasy
A residential building inspection reveals that the foundation drain for a newly constructed home is a 3-inch diameter pipe. The drain is intended to collect groundwater and discharge it to an approved daylight outlet. According to the 2021 IRC, what is the minimum diameter required for a foundation drain pipe?
- A3 inches
- B6 inches
- C4 inches
- D2 inches
Show answer & explanationAnswer & explanation
Correct answer: C. 4 inches
IRC R405.1 specifies that foundation drains shall be a minimum of 4 inches in diameter.
Why the other options are wrong
- A. Incorrect. 3 inches is below the minimum required diameter by the IRC.
- B. Incorrect. While 6 inches would be adequate, it is not the minimum required diameter.
- D. Incorrect. 2 inches is too small and would likely clog easily or not handle sufficient flow.
Minimum Foundation Drain Pipe Diameter
The smallest allowable internal dimension for a foundation drain pipe, as mandated by building codes to ensure adequate water flow.
- IRC R405.1 outlines foundation drainage requirements.
- Ensures sufficient capacity to remove groundwater.
- Prevents clogging and hydrostatic pressure buildup.
- A common code requirement for residential foundations.
Memory trick: A foundation drain needs a 'four-inch' pipe to keep the water flowing free.