What is the minimum discharge size on a grinder pump?

• A. 1/2 inch
• B. 1-1/2 inch
• C. 2 inch
• D. 1-1/4 inch

Answer: (D)

Grinder pumps push ground wastewater through a discharge line, so the outlet must be large enough to carry solids without clogging while still being cost-effective and compatible with standard sewer connections. The minimum discharge size commonly used for this setup is 1-1/4 inch. This size strikes a balance: it’s big enough to pass the solids formed after grinding and avoid frequent jams, yet not so large that it adds unnecessary cost or creates excessive friction losses. A smaller size, like 1/2 inch, would clog easily with typical grinder slurry; a 1-1/2 inch discharge isn’t the minimum (it’s larger than needed in most cases), and 2 inches would be more than what’s usually required for standard grinder-pump installations.