An indirect-waste standpipe receiving a domestic clothes washer must have a trap, and the standpipe height above the trap weir must generally be within what range?

Explanation

A clothes-washer standpipe must be trapped and vented, and the standpipe usually extends between 18 and 30 inches above the trap weir. Too short a standpipe can overflow during the wash pump-out; too tall creates back-pressure and slow draining. The trap is set at an accessible height below the standpipe.