IPC Storm Drainage Systems 2

Question 1

Per the IPC, what is the minimum allowable size for a roof drain?

Accepted Answer

3 inches

Answer

The IPC specifies that roof drains shall not be less than 3 inches in size, regardless of the calculated drainage area.

Question 2

Under the IPC, horizontal storm drainage piping larger than 3 inches in diameter must have a minimum slope of:

Accepted Answer

1/8 inch per foot

Answer

Horizontal storm drain pipes larger than 3 inches in diameter require a minimum slope of 1/8 inch per foot, less than the 1/4 inch required for smaller pipes.

Question 3

According to the IPC, are combined sanitary and storm drainage systems permitted in new construction?

Accepted Answer

No, except where specifically approved by the administrative authority

Answer

The IPC prohibits combined sanitary and storm drainage systems in new construction unless the administrative authority specifically approves it, such as where the public system is combined.

Question 4

Per the IPC, subsoil (foundation) drainage systems must discharge to:

Accepted Answer

An approved location such as a storm drain, combined sewer (where approved), or daylight

Answer

Subsoil drain systems must discharge to an approved location, which can include a storm drain or an approved point of disposal such as daylight — not into the sanitary system.

Question 5

When sizing a storm drainage system under the IPC, which of the following factors is NOT used to calculate drain pipe sizes?

Accepted Answer

Soil percolation rate

Answer

Storm drain sizing uses rainfall intensity, drainage area, and pipe slope; soil percolation rate applies to subsurface absorption systems like septic fields, not storm drains.

IPC - International Plumbing Code Practice Test

IPC - International Plumbing Code Practice Test

IPC Storm Drainage Systems 2