Jetting grease lines: how to actually remove fats, oils and grease

01 /How does grease block a drain?

Grease blocks a drain gradually, by coating the wall rather than forming one plug. Warm fats and oils go down the sink as liquid, cool as they travel, and solidify on the cooler pipe wall, especially where flow slows: long horizontal runs, fittings, and sags. Each new layer traps food particles, coffee grounds and soap. Over time the bore shrinks until a normal amount of kitchen waste stops the line.

Soap chemistry makes it worse. Fats can react with calcium and other minerals in wastewater to form harder, soap-like deposits that resist hot water and detergent. These deposits are one reason municipal sewer operators spend so much effort on FOG in commercial areas.

02 /Why does snaking a grease clog keep failing?

Snaking a grease clog keeps failing because the cable only removes the grease directly in its path. A cutter perhaps two or three inches wide spins through a two-inch or three-inch line that has lost most of its bore to grease, opens a hole, and drains the backed-up water. The grease on the rest of the wall stays in place, and the next few weeks of dishwater and food waste close the hole again.

That pattern, a clog that returns after every snaking, is the most common reason homeowners and restaurants switch to jetting. The comparison is laid out in hydro jetting vs snaking.

03 /What is the right way to jet a grease line?

1. Find the best access

   A cleanout on the kitchen branch or building drain is ideal. Jetting through a sink trap arm is possible for short branches but gives the nozzle a tight turn and limited travel.

2. Open the line if it is stopped

   A penetrating nozzle, or sometimes a small cable, opens a path so water and grease have somewhere to go.

3. Clean with a rotating nozzle

   A rotating head scrubs the full circumference. Heavier grease often calls for a weighted rotating head. Hot water, where the rig has it, softens hardened fats.

4. Work in sections and pull back slowly

   Grease comes off in chunks. Advancing and retreating in sections, with adequate flow, keeps those chunks moving downstream instead of re-forming a plug.

5. Flush all the way to the main

   Grease pushed only part way can settle at the next fitting or sag. The job is the whole run from fixture to building sewer.

6. Verify with a camera

   The camera shows whether the wall is clean and whether a sag or offset is where grease keeps collecting.

04 /Which nozzles are used for grease?

Nozzle families are explained in jetting nozzles explained, and the physics of why flow matters for carrying grease away is in pressure vs flow.

05 /Where does grease usually collect in a house?

• The kitchen sink branch, especially long horizontal runs to the stack in basement ceilings or through exterior walls.
• Where the kitchen branch joins the building drain, where flow slows and changes direction.
• Sags or bellies in the building sewer, where water pools and grease floats and sticks.
• Near floor drains in older homes where a kitchen line ties into the basement drain system.
• Upstream of an offset joint, where the step in the pipe traps debris.

The location tells the operator where to start and which access to use. A clog limited to the kitchen sink usually sits in the kitchen branch, so jetting from a branch cleanout or the trap arm makes sense. If the kitchen, laundry and basement floor drain all slow down together, the grease has likely reached the building drain or building sewer, and the job starts at the main cleanout with a larger hose and nozzle. A camera pass after cleaning shows whether a sag or offset is the collection point; if it is, grease will keep returning to the same spot until that defect is repaired.

Dishwashers and garbage disposals add warm water and food solids to the same line. A disposal does not remove the grease problem; it adds more particles for the grease to trap. Many disposal manufacturers also advise against pouring chemical drain openers into the unit; safer first steps for a slow disposal, and for toilets, septic systems and RVs, are in which drain cleaner is safe for toilets, septic and RVs.

06 /How are commercial kitchen grease lines different?

Commercial kitchens produce far more FOG, so their lines typically discharge through a grease interceptor (sometimes called a grease trap) that separates floating grease and settling solids before wastewater reaches the municipal sewer. The line between the kitchen fixtures and the interceptor collects grease fast and is often jetted on a schedule. Municipal sewer-use bylaws commonly regulate interceptor sizing, maintenance and pump-out frequency; the specifics vary by municipality, so confirm the rules with your local utility (in Calgary, start with 311).

Jetting the line does not replace pumping the interceptor, and pumping the interceptor does not clean the line. They are separate maintenance tasks. The commercial and municipal jetting guide covers interceptors and vacuum trucks in more depth.

07 /How do you keep a grease line clear after jetting?

1. Scrape plates and pans into the compost or garbage before washing.
2. Let cooking oil cool and dispose of it in a sealed container, or use a municipal household hazardous waste or cooking oil drop-off if available.
3. Use a sink strainer and empty it into the garbage.
4. Do not rely on running hot water after grease; it moves the grease a few metres further before it cools and sticks.
5. Be cautious with chemical drain cleaners. They can generate heat and fumes, can damage some pipe, and create a hazard for anyone who later opens or jets the line; see drain cleaner vs hydro jetting.
6. In a restaurant, keep the interceptor maintenance log current and schedule line jetting before symptoms appear.

Not sure whether your slow kitchen drain is grease or something else? Run it through the jet-or-auger decision tool, or request quotes through the quote form.

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