A. Determine the total number of gallons that will be dumped at one time by all present and future washers. Use fill volumes at high level to get this total (if only 1 washer will use the trench, use level at overflow.)

NOTE: Always assume worst case, i.e. all washers will drain at the same time from the highest level.

B. Divide the total gallons to drain by 7.48 gallons per cubic foot. The result is the minimum volume of the drain trench in cubic feet.

C. Size the length width and depth of the trench to meet the above minimum volume and any other parameters, such as washer foundation width, available floor space, etc.