What is the maximum horizontal drainage run length before a cleanout is required?

What is the maximum horizontal drainage run length before a cleanout is required?

• A. 50 ft
• B. 75 ft
• C. 100 ft
• D. 125 ft

Answer: (C)

Access for cleaning and snaking is the key idea here. In horizontal drainage piping, you must provide a cleanout so a blockage can be reached and cleared. The standard rule is that no portion of a horizontal drain should be more than 100 ft from a cleanout. So when you design or inspect a system, you place cleanouts so the distance along the pipe between them (and from fixtures as needed) does not exceed 100 ft. That’s why 100 ft is the correct maximum. The other distances would either require more cleanouts or exceed the common limit, making maintenance more difficult.

Access for cleaning and snaking is the key idea here. In horizontal drainage piping, you must provide a cleanout so a blockage can be reached and cleared. The standard rule is that no portion of a horizontal drain should be more than 100 ft from a cleanout. So when you design or inspect a system, you place cleanouts so the distance along the pipe between them (and from fixtures as needed) does not exceed 100 ft. That’s why 100 ft is the correct maximum. The other distances would either require more cleanouts or exceed the common limit, making maintenance more difficult.