Schedule calculator
How often to pump a grease trap
Start with Houston’s default: a full interceptor evacuation about every 90 days. Then tighten the window if the line is heavy, the trap is small, or you are already near the 25% rule. A waiver toward 180 days exists on paper — it is not a DIY extension.
Houston’s 90-day default
The City of Houston Health Department states that Sec. 47-512(b) requires interceptors inside the incorporated city limits to be fully evacuated at least quarterly (every 90 days) unless a Notice of Waiver is submitted and approved. “Fully evacuated” means empty — not skimmed off the top.
If the kitchen sits in a MUD, an ETJ, or another city, do not copy Houston’s calendar blindly. Ask the utility or health authority, then put that interval on your vendor contract. See the Houston FOG explainer for city-limits vs MUD context.
The 25% rule
Independently of the calendar, a trap is generally considered overdue when floating FOG plus bottom solids take up about 25% of the wetted height (a sludge-judge reading). High-volume fry programs can hit that mark in 30 days even in a 1,000-gallon tank. Treat 90 days as a Houston ceiling, not a target for a busy line.
Kitchen load factors
Gallons on the lid are only half the story. What you cook, how many covers you turn, and how many hours the fryers run decide whether 90 days is safe. The calculator above uses a simple light / medium / heavy proxy so you can plan — then confirm with a reading.
- Light — bakery, coffee, limited fry, low covers. Houston still defaults to 90 days unless a waiver is approved.
- Medium — typical full-service with one or two fryers. Many kitchens land in a 45–90 day window.
- Heavy — QSR, wok, late night, banquet, or 3+ fryers. Plan on 21–45 days so you do not fail the 25% rule.
Common questions
How often do restaurants pump a grease trap in Houston?
Inside the incorporated City of Houston, interceptors are generally fully evacuated at least every 90 days unless the Health Department approves a Notice of Waiver. Busy fry lines often need service sooner so the trap stays under the 25% solids and floating-FOG mark.
What is the 25% rule?
A common pretreatment standard: combined floating fats/oils/grease plus bottom solids should stay below about 25% of the trap’s wetted height. If a sludge-judge reading is near that line, pump now — even if 90 days have not passed.
Can I stretch to 180 days on my own?
No. Houston’s waiver path is an application with records and usually a permitted transporter certification. Approval is not automatic, and a full evacuation at least every 180 days still applies if a waiver is granted.
Do under-sink traps follow the same calendar?
Indoor hydro-mechanical traps (often under 100 gallons) fill much faster than outdoor gravity interceptors. Kitchens typically service them every 1–4 weeks. If you have both, schedule each device on its own interval.