Laterals are the small branch lines from kitchen fixtures and floor drains. The main is the larger line that carries everything out to the city sewer. They need different hoses and machines, and grease moves from one to the other, so cleaning only one leaves the other coated and the problem comes back.
How is jetting a lateral different from jetting the main?
The pipes are different sizes, so the tools are too. Small lines take a small hose and a machine that fits indoors. Spartan Tool describes its portable electric jetter as one that "will clean the entire circumference of the line and make quick work of grease and soft clogs," at 1,500 PSI and 2.0 GPM. General Pipe Cleaners, another maker, says "Electric sewer jetters typically offer a maximum of 1,500 psi at about 2 gpm." That is enough force for a branch line, and it is small enough to carry into a kitchen.
A building main is longer and larger. General Pipe Cleaners says a gas-powered jetter gives "twice the pressure and flow rate of electric jetters to handle larger and longer lines." Gas machines can still work inside a building with a portable reel: "This lets you use the power of gas sewer jetters in buildings and confined spaces where exhaust fumes could be hazardous, while the jetter motor stays safely outside."
In practice for a restaurant, that works out like this:
| Laterals | Main line | |
|---|---|---|
| What it is | Branch lines from sinks, dish machines, floor sinks and floor drains | The line that gathers the branches and runs out to the city sewer |
| Where the crew works from | Inside, through floor drains, cleanouts or a removed fixture | Usually an outside cleanout or a cleanout near where the line leaves the building |
| Hose and machine | Small hose on a compact machine | Larger hose and a bigger machine, often with the engine kept outdoors |
| What typically builds up | Grease, food solids and scale close to the fixtures | Grease that has cooled and collected, plus roots or sediment in older pipe |
| Why it matters to the kitchen | Slow sinks and floor drains that gurgle | Several drains backing up at once |
HQ Plumbing & Air jets restaurant lateral lines from the inside with a small hose, and separately jets the main out to the city sewer.
Why do both get cleaned?
Because they feed each other. Grease starts warm and runs fine, then cools in the pipe and sticks. Phoenix Water Services says the biggest problem in its sewers is "coagulated grease and cooking oil," which "will cool as it enters the sewer line and it will coagulate, causing a blockage." The same thing happens inside a building. The lateral gets coated first, then what breaks loose travels to the main and settles there.
Cleaning only one side leaves a loose end:
- Jet the laterals but not the main. Loosened grease can flow into a main that is already narrowed and catch there. The stoppage moves instead of leaving.
- Jet the main but not the laterals. The main is open, but the branch lines may still be coated, so sinks stay slow and floor drains still smell. The same fixtures keep sending grease into the main.
EPA's fact sheet on sewer cleaning makes a related point about flushing: it "only achieves temporary movement of debris from one section to another in the system." The goal is not to push the grease along. It is to take it out through an access point, which is why a good crew works in an order that moves debris toward a cleanout it can reach and checks afterward with a camera. Our page on why a camera check follows hydro jetting explains that last step.
Jetting the lines also does not replace servicing the grease interceptor. That is a different device with different rules; grease trap pumping versus cleaning versus jetting covers how they fit together, and grease in the sewer lateral after the trap covers what builds up past it.
Who is responsible for which line in Phoenix?
The owner, nearly all the way to the city's pipe. Phoenix Water Services says that "we are only responsible for city owned infrastructure which are portions of the system that reside in dedicated right of ways and or utility easements," and that "Everything from the connection to that system or point, back to the house or business is responsibility of the home or business owner." On cleanouts, Phoenix adds that those on private property "fall outside the jurisdiction of city staff."
So your laterals and your main both sit on the property side, and cleaning them is your job. Other Valley cities have their own wording, so check your city's sewer program if the building is outside Phoenix.
Where does the crew get in?
At cleanouts, and the code says where those go. The 2024 International Plumbing Code (IPC) puts it this way: "The junction of the building drain and the building sewer shall be served by a cleanout that is located at the junction or within 10 feet (3048 mm) of the developed length of piping upstream of the junction." It also calls for cleanouts at spacing of not more than 100 feet on horizontal drains and building drains, and at changes of direction over 45 degrees. Phoenix's amendment list for the 2024 IPC does not change Section 708. Our page on where code requires cleanouts goes deeper, and hydro jetting without an accessible cleanout covers what happens when there isn't one.
How do you tell which line has the problem?
Use the symptoms. A single slow sink, a floor drain that gurgles or a smell at one spot usually means a lateral. Several fixtures backing up together, or a floor drain filling when a distant fixture drains, points to the main. Our page on telling a main line clog from a branch clog walks through the tests.
For restaurants that run steady grease loads, jetting is often routine rather than an emergency. We log the date of each visit in the customer's record, so the schedule can be set from what the lines actually did. How often a commercial building should have its drains cleaned covers how to set it. HQ gives free estimates with upfront pricing, is licensed and insured, and works restaurant lines before open or after close.