What Is the 25% Rule? 

For restaurant managers, business owners, and facility teams, the 25% Rule provides a practical way to determine when a grease interceptor needs attention. Under current WSSC Water requirements, fats, oils, grease, and solids should not accumulate beyond 25% of the interceptor’s liquid-retention capacity.  

Understanding that threshold can help you plan grease trap maintenance before excessive buildup begins affecting the system. 

What Is the 25% Rule? 

The 25% Rule means the combined accumulation of fats, oils, grease, and solids cannot exceed 25% of a grease interceptor’s liquid-retention capacity under WSSC Water requirements. 

For example, if buildup reaches the applicable 25% threshold before your normal service date, the interceptor needs to be cleaned sooner. WSSC Water also requires volume-based grease interceptors to be maintained at least quarterly, according to manufacturer recommendations, a Code Official’s direction, or the 25% Rule- whichever requirement is more stringent. 

Because requirements vary by jurisdiction and equipment type, facility managers should confirm the rules that apply to their property. 

Why Is the 25% Rule Important? 

The rule helps ensure that a grease interceptor retains enough usable capacity to continue managing fats, oils, grease, and solids effectively. 

As material accumulates, the interceptor has less available capacity. Without proper pumping and cleaning, buildup can contribute to odors, slow drains, backups, overflows, and disruptions to commercial kitchen operations. 

Following an appropriate maintenance schedule can also make service more predictable rather than waiting for drainage problems to signal that the interceptor is overdue. 

How Can Magnolia Help with Grease Interceptor Maintenance? 

Magnolia provides commercial grease trap and interceptor services throughout Washington, DC, Maryland, and Northern Virginia. Our services include: 

• Grease trap and interceptor pumping 

• Complete grease trap cleaning 

• Preventive maintenance programs 

• Grease interceptor repair and replacement 

• High-pressure water jetting 

• Commercial drain and sewer cleaning 

• Liquid-waste pumping 

Magnolia has served businesses in the Washington region since 1950 and provides responsive service backed by specialized commercial equipment. 

Schedule Grease Trap Service with Magnolia 

If you are unsure whether your interceptor is approaching the 25% threshold, Magnolia can help you establish a practical maintenance approach for your facility. 

Call 301-304-7064 or contact Magnolia online to schedule grease trap pumping, cleaning, or maintenance in Washington, DC, Maryland, or Northern Virginia.