How Often Should a Grease Trap Be Cleaned? A Guide for Midrand & Johannesburg Kitchens

A grease trap that’s overdue for cleaning doesn’t usually announce itself until it’s already a problem — a slow kitchen drain, a bad smell near the back door, or worse, a failed inspection. For restaurants, cafes and office-park food courts across Midrand, Johannesburg and Pretoria, getting the cleaning schedule right is a compliance issue as much as a plumbing one.

How often, realistically

Most commercial kitchens need their grease trap cleaned every 4-8 weeks, but that range hides a lot of variation. A high-turnover fast food kitchen frying continuously can fill a trap in under a month, while a smaller office-park cafe doing mostly grills and light prep might genuinely stretch to 8-10 weeks. The only way to know your actual number is to check the trap directly rather than guess from a generic schedule — once you’ve measured it a few times, the pattern for your specific kitchen becomes obvious.

The 25% rule

The standard industry guideline is to clean the trap once the combined fat, oil and grease layer reaches about a quarter of its total capacity. Past that point, the trap’s effective capacity drops fast, and it stops doing its job properly well before it visibly overflows — meaning grease is already passing through into the line before anyone notices a problem.

Two different metros, two different bylaw regimes

This is the part that catches out businesses operating across this region specifically: a restaurant in Midrand or elsewhere in Johannesburg falls under City of Johannesburg’s trade effluent requirements, while a kitchen in Pretoria falls under City of Tshwane’s. The two metros don’t necessarily enforce identical standards or inspection cadences, so a compliance schedule that worked at a previous location in the other metro isn’t something to assume still applies. Check directly with the relevant metro’s trade effluent department, or ask your plumber to confirm what applies to your specific address — not just “Gauteng” in general.

What neglect actually costs

• Grease discharging into the municipal sewer line — a bylaw violation in both metros, not just an inconvenience
• Recurring blockages in your own kitchen drain lines, usually at the worst possible time during service
• Odour building up near the trap and, eventually, through the kitchen itself
• A failed health inspection, which can mean a fine or, for repeat or serious violations, a temporary closure

Getting a schedule that actually fits

The right interval depends on kitchen size, how much frying and oil-heavy cooking you do, how the trap is sized relative to your output, and which metro’s bylaw applies. A scheduled cleaning contract sized to your actual volume — rather than a generic “quarterly” default — is what keeps a busy Midrand or Johannesburg kitchen compliant without paying for cleanings it doesn’t need, or worse, running past the point where the trap’s already failing.