What happens when a grease interceptor baffle or tee breaks?

A baffle is a wall or divider inside the tank. The inlet fitting and the outlet tee are pipe pieces that control where water enters and where it leaves. Together they make the water travel slowly through the tank so grease can float and solids can settle.

The National Precast Concrete Association guidelines say an inlet baffle or diverter is necessary to increase retention time and avoid short-circuiting. They also say an outlet baffle or tee is necessary. The same guidelines note that baffles increase retention time and prevent short-circuiting.

Short-circuiting means water takes a quick path from the inlet to the outlet. It skips the time in the tank that the design counts on. That is the core risk of a broken part.

### What the code says the parts must look like

Mesa's city code is unusually specific. Under Section 8-4-22, an interceptor must be:

• A minimum of 500 gallons and built with at least two chambers.
• Built with inlet piping that has a 90 degree elbow and a minimum 18 inch down spout.
• Built with outlet piping that has a tee connection and a threaded cover, also with a minimum 18 inch down spout.
• Given three chambers, each with a manway, once the calculated size reaches 750 gallons or more.

Phoenix also requires gravity interceptors to have at least two compartments, and the Phoenix approved-interceptor list repeats that. The manual does not spell out inlet and outlet fitting dimensions the way Mesa's code does. Your city's approved model list and your plan set are the source for those details.

### What a failed part can do

Here is what the sources support, and what they do not.

• The tank may pass grease it should have held. A missing outlet tee or a cracked baffle changes the flow path. The idea behind a down spout is that the outlet draws water from lower in the tank, away from the floating layer. That is an explanation of the design, not a measured result for any one tank.
• The tank can fail an inspection even when it is not full. Phoenix inspectors check the interceptor to see if any parts are missing or if the interceptor has rotted out and needs to be replaced. They also check how much grease is in it.
• A cleaning schedule may stop being enough. Chandler says that if FOG material is witnessed leaving a treatment device, the cleaning frequency must be increased. Grease leaving the device is also a reason to look for a failed part before you just add more pump-outs.

Broken internal parts do not always mean a full tank replacement. They do mean the tank is not doing the job the city approved it for.

Almost nobody finds it by looking at the lid. It comes out in one of four ways.

### At a pump-out

Phoenix's manual lists witnessing the interceptor cleaning as a best practice and says it is also a good time to inspect for damaged or missing parts. That is the easiest moment. The tank is empty and the parts are visible.

Ask the pumper to tell you before they leave if anything looks loose, cracked or gone. Ask for a written note or photos. Our page on what happens during a grease trap cleaning walks through the visit.

### At a city inspection

Phoenix inspections are unannounced. The manual says the inspector will check the interceptor for missing parts or rot, and that if a broken or missing part is found, the inspector will issue a requirement to clean, replace, repair or do whatever is needed. The time frame depends on the impact on the sewer system and how much work the fix takes. Extensions can be granted based on business needs if the request is in writing, but the extension does not stop the city from taking enforcement action if a sewer blockage or other violation occurs in the meantime.

Tempe's inspection page says grease control devices must be in good condition with no holes, missing or broken parts or severe corrosion. More detail on what inspectors look for is in what city inspectors check on a grease trap.

### When grease shows up downstream

A tank that is failing inside can send grease into the building sewer. If you see grease leaving the device, or you get repeat slow drains between pump-outs, treat that as a sign to inspect the parts. See kitchen drain overflowing for what to do during a backup.

### At a scheduled parts inspection

Some utilities require this on purpose. The San Antonio Water System, a Texas utility, requires an annual inspection by a licensed plumber or other qualified professional after the tank is emptied. The report has to include photos of all inlet and outlet fittings, internal baffles, walls and floor. Its checklist asks whether the sanitary tees or elbows on the inlet and outlet sides are clogged, loose or damaged, and whether all internal baffles are secure and in place. It requires defects to be corrected within 90 days of the inspection.

That is a Texas rule, not a Valley rule. It is a useful template, though. The Valley cities in this area do not publish an annual parts checklist like it in the pages we read, so ask for those photos yourself at each pump-out.

A broken baffle or tee is fixed by emptying the tank, finding the failed part, repairing or replacing it, and logging the work. The city wants to see the record. The order matters.

1. 1Have the tank fully pumped and cleaned. Phoenix says the interceptor must be left completely empty after pumping. You cannot see a cracked baffle under a foot of grease and water.
2. 2Get a written finding. Which part failed, where it sits, and what shape the walls and floor are in. Photos help.
3. 3Choose repair or replacement. A loose or missing tee or elbow is a fitting job. A collapsed or cracked baffle wall, or walls that are rotted out, points toward replacing the tank. Phoenix's manual says an interceptor that has rotted out needs to be replaced.
4. 4Check the permit question before work starts. Phoenix's manual says all grease interceptors installed and replaced must go through plan review. It does not say how it treats a repair to a part inside an existing tank. Ask Phoenix Environmental Services before you assume either way. Our page on permits for interceptor replacement in the Valley covers the replacement side, and the code library has the Phoenix replacement plan review page.
5. 5Log it. Chandler says records for pumping, cleaning, maintenance and repairs should be kept on site for 3 years. Its list of what a record includes has a line for the nature of service performed, and the examples in it include replaced baffle. Phoenix also requires records to be available at the facility for a minimum of 3 years. Our maintenance log page shows a simple format.
6. 6Keep the photos with the record. If the city asks later, the before and after pictures answer the question quickly.

Under Phoenix City Code 28-15, the user must keep the interceptor in continuously effective operating condition, and that minimally includes necessary repairs to internal structures. Mesa's code puts the same weight on the owner, at the owner's expense. In Chandler, the owner of the device pays for cleaning, maintenance and repairs. In a leased space, who covers it can also come down to your lease, which the codes do not decide.

### Why this is not a do-it-yourself job

The inside of a tank is a confined space by OSHA's definition. Its rule says a confined space is large enough for a person to enter and work, has limited or restricted means of entry or exit, and is not designed for continuous occupancy. It lists tanks, vessels and pits as examples of spaces that may have limited entry. Such a space becomes permit-required if it contains or may contain a hazardous atmosphere, or has another serious hazard.

Whether a given grease tank meets the permit-required test depends on the tank and the day. That is why entering one is a job for trained people with the right equipment. Do not climb in to fix a tee yourself.

### Can shared or older tanks be different?

Yes. A tank shared by several tenants has an owner and users, and repairs turn into a landlord and tenant question. See shared grease interceptors at strip centers.

Call one when a pump-out report says a baffle, tee or elbow is broken, missing or loose. Call when an inspector writes up a broken part, since the city sets a deadline. Call when grease is showing up downstream of a tank that was recently pumped.

A licensed and insured plumber can look at how the tank ties into your drain lines, tell you whether it is a fitting fix or a bigger job, and help you sort out what the city needs to see. HQ Plumbing and Air handles commercial plumbing, gives free estimates, and states the price up front before work starts. If the kitchen is backing up now, we offer 24/7 emergency service. See our commercial plumbing page.

For related reading, see how big an interceptor needs to be, how installation steps work and where an interceptor can go and how it must be reached.

Wondering how long the tank itself lasts? See how long a grease interceptor lasts. Deep tanks are hard to inspect; see when a riser or extension collar is needed. If the concrete around the baffles is crumbling too, see why concrete grease interceptors corrode.