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Disposing of fats, oils and grease

How do fats, oils and grease cause sewer backups?

When liquid fats, oils and grease are washed down the sink or toilet, these materials solidify and stick to the inside of your plumbing or to City sewer pipes. This can result in a blockage and lead to sewer backups. 

Where do fats, oils, and grease come from?

Most fats, oils and grease are a result of cooking, and can be found in meats, fats, lards, cooking oil, shortening, butter and margarine, salad dressings, and dairy products.

What can you do to help prevent sewer backups?

  • NEVER pour fats, oils or grease down sink drains or toilets.
  • DO NOT use hot water or chemicals to flush grease down the drain.
  • DO NOT install or use a food grinder in your kitchen sink.
  • ALWAYS place strainers into sink drains to catch food scraps.
  • For restaurant owners the installation of a grease interceptor is mandatory, and is regulated under Sewer Use By-law 2003 - 514.

Tips on how to properly dispose of fat, oil and grease

  • Let grease cool and harden, then scrape it from trays, plates, pots and pans, and grills into your green bin.
  • Pour liquid cooking oil or any liquid food waste into a biodegradable container (such as a milk carton) and place into your green bin.
  • Absorb all liquid fats, oils, or grease with paper towels and place the soiled paper towels into your green bin.
  • Not sure how to dispose of an item or substance? Use our Waste Explorer to find out.

For more information, please contact a representative of the Sewer Use Program at 613-580-2424 ext. 23326.

Pool and hot tub discharge guidelines

To practice responsible maintenance for swimming pools and hot tubs, it is important to discharge pool and hot tub water appropriately. Storm sewers divert rainwater and snowmelt into the nearest stream, creek, pond or river without treatment at the City’s wastewater treatment plant. Chlorinated water and saltwater from pools and hot tubs contain chemicals that are harmful to the aquatic life living in Ottawa’s waterways, and should never be discharged to a storm sewer.

Below are two examples of storm sewers, which lead directly into the City's waterways:

Catch basin
Catch basin with fish symbol.

Please take a moment to review the City’s pool and hot tub discharge guidelines:

Pool and hot tub openings

  • Standing water on pool covers such as rainwater or snowmelt may be discharged to the homeowner’s property provided that it is properly absorbed into the ground and does not impact neighbouring properties; or
  • Standing water on pool covers such as rainwater or snowmelt may be discharged to the storm sewer, provided that debris and leaves are removed from the water prior to discharge.

Pool and hot tub maintenance (backwash)

  • Backwash from pool and hot tub maintenance may be discharged to the homeowner's property, provided that it is properly absorbed into the ground and does not impact surrounding properties; or
  • Backwash from pool and hot tub maintenance may be discharged through a connection to the sanitary sewer. Contact a licensed plumber for more information.

Pool and hot tub closure

  • Water may be discharged through a connection to the sanitary sewer. Contact a licensed plumber for more information.
  • Water may be discharged onto the homeowner's property provided that it is absorbed into the ground without:
    • flowing onto adjoining properties,
    • flowing over a valley or into a ravine, or
    • causing erosion;
  • Water may be transported by an appropriately licensed wastewater hauler.


The City of Ottawa’s Sewer Use By-law (2003-514), Section 18, regulates the disposal of pool and hot tub water. Contravention of the by-law may result in further enforcement or fines. If you have any questions or concerns please contact the Sewer Use Duty Officer at 613-580-2424, extension 23326 or by email at sup-pue@ottawa.ca.

If your pool water has entered a stream, river, lake or storm sewer system without proper treatment, you and your pool service provider are legally obligated to report the discharge to the Ministry of the Environment, Conservation and Parks (MECP) - Spills Action Centre (1-800-268-6060) and the City of Ottawa (3-1-1).

What NOT to flush down the toilet

Your toilet is not a green bin or a garbage can. Flushing certain items can result in a sewer backup into your home and can create problems at the City's wastewater treatment plant.

Only flush the three Ps – pee, poo and toilet paper! These are the only items that belong in your toilet.

The following items should never be flushed down the toilet:

  • Personal care wipes/baby wipes
  • Diapers
  • Cotton swabs
  • Hair
  • Dental floss
  • Tampons
  • Sanitary products
  • Condoms
  • Old medicines
  • Grease/fat from food
Visual: animated icons appear with a big red diagonal bar

There’s no such thing as a “flushable” wipe. Wipes don’t break down in the City’s sewer system.

Visual: animated icons appear with text

Neither do –Diapers, cotton swabs, hair, dental floss, sanitary products, cotton pads, condoms, old medicine, bandages, cigarette butts, nd grease, oil, and fat.

Visual: animated pipe clogs

These items can clog your pipes and the City’s sewers, which is costly and gross.

Visual: toilet appears

Only flush the three Ps – pee, poo and toilet paper.

Visual: Ottawa logo appears

How can I dispose of these items?

Visit the Waste Explorer to find out how to dispose of these items.

Why shouldn't "flushable" wipes be flushed down the toilet?

While products may be advertised as "flushable," in reality items such as baby wipes, makeup remover cloths, and disinfectant wipes do not decompose in the sanitary sewer system. Flushing this material causes damage to the sewer system and may cause sewer backups in your home. These products should be disposed of in the garbage.

Wastewater: Frequently asked questions

Answers to the most commonly asked questions about wastewater. If you have a question that is not addressed, please call 3-1-1.

Why is the storm drain in front of my home not draining faster when it rains?

Sometimes, it seems the catch basins are not handling enough water to drain the street properly. This can be caused by debris such as leaves or grass clippings obstructing the grate. Your help in keeping the grates free of debris is valued and appreciated.

If the catch basin grate is clear and clean but does not drain quickly enough during heavy rainstorms, it may not mean the storm system is not functioning. During heavy rainstorms, the short term storage of rainwater on the streets is one of the means to avoid overwhelming the storm water collection system and the means to avoid the possibility of flooding basements. It is much better to have water on the street for a short duration than to have sewer backups. To prevent sewer backups, the City has restricted the catch basin capacity to match the capacity of the pipes.

Where does rain water go?

The City of Ottawa has three types of sewers: sanitary, storm and combined.

  • Sanitary sewers collect wastewater from homes, businesses and industrial sites, and transport the waste water through a network of sewers, pumping stations and forcemains to trunk sewers which direct flow to the Robert O. Pickard Environmental Centre for treatment before being discharged to the Ottawa River.
  • Storm sewers carry rainfall and other surface water run-off directly to the nearest creek, stream or river, generally without treatment.
  • Combined sewers collect and transport a mixture of both sanitary and storm water in a single pipe. Combined sewers only exist in a very small area of the City. Geographically most of the City is serviced by separated sewers. Most of this flow is transported to treatment plants, but when the 2.4m diameter pipe collecting the combined sewage is flowing at full capacity, the excess overflows to the river to prevent sewer backups into basements. This legacy system was designed and built when 100% of the city sewage was flowing directly to the Ottawa River. Today, 99.7% of sewage is fully treated. 

The frequency and duration of the overflows within a combined sewer system depends on the volume of precipitation in a particular area and the sewer characteristics of the area. Some combined sewers rarely overflow, while others overflow when it rains.

What is a combined sewer overflow?

Learn more about combined sewer overflows.

What is the City doing to reduce spills to the Ottawa River?

Learn what the City is doing to reduce spills to the Ottawa River.

How do I properly discharge my pool water?

Learn maintenance tips for swimming pools and hot tubs.

How do I dispose of RV waste?

How do I dispose of RV waste?

The Robert O. Pickard Environmental Centre (ROPEC) accepts waste from recreational vehicles (RV) such as trailers, camper vans, and motor homes. This service is free of charge. 

From April to November, please present yourself at the front gate:


800 Green Creek Drive, Ottawa

Monday to Friday between 8:00 am and 2:30 pm

  • closed on statutory holidays

You will be directed to wait in a designated area until City staff becomes available to escort you to the discharge location and assist you. Water for flushing your tank will not be provided on site. Closed toed shoes and work gloves are recommended while on-site. Please note, general information will be requested in order to complete a log sheet for tracking purposes.

From December March, please contact the Sewer Use Duty Officer at 613-580-2424 ext. 23326 at least 24 hours prior to arrival to arrange an appointment during regular business hours of Monday to Friday between 8:00 am and 2:30 pm (closed on statutory holidays). 

Why shouldn't "flushable" wipes be flushed down the toilet?

While products may be advertised as "flushable," in reality items such as baby wipes, makeup remover cloths, and disinfectant wipes do not decompose in the sanitary sewer system. Flushing this material causes damage to the sewer system and may cause sewer backups in your home. Flushables should be disposed of in the garbage.

What is wastewater?

Wastewater is water that has been used and discharged by homes, businesses and industries. Domestic wastewater includes typical wastes from the kitchen, bathroom and laundry. Wastewater is thoroughly treated at the Robert O. Pickard Environmental Centre to ensure it is safe for the public’s health and the environment.

How does the wastewater treatment plant work?

Find out how the City treats wastewater at the Robert O. Pickard Environmental Centre (ROPEC).

What do I do if my basement floods due to a sewer backup?

Learn what to do if your basement floods due to a sewer backup.

How do I apply for the Residential Protective Plumbing Program? 

The City offers assistance to eligible homeowners to cover the cost of installing protective plumbing devices. For more information, consult information on the Residential Protective Plumbing Program.

What is a blow-back and why do they happen?

Learn about blow-backs and why they happen.

Educational materials

Let’s Explore Wastewater Treatment (brochure)

Download a printable version of the wastewater treatment process brochure.

Wastewater Treatment Plant - Robert O. Pickard Environmental Center

The Robert O. Pickard Environmental Centre (ROPEC) is located in the city's east end, right next to the Ottawa River. Using an extensive sewer system, all of the wastewater is collected from homes and businesses between Stittsville, Orleans and Manotick.

Whenever we use water, we contaminate it - whether we flush the toilet, take a shower, wash dishes, or do the laundry.  All of this water can be easily treated at ROPEC.  Other materials are more difficult to break down or remove, such as deodorants and some hair care products.

Substances like oil or paint are not meant to be treated by a municipal sewage plant. For information on how to properly dispose of hazardous waste, check out the Waste Explorer.

Ottawa's wastewater treatment plant:

  • Cleans an average of 390 million litres of wastewater every day - enough to fill more than 6,000 backyard swimming pools
  • Protects the environment.  When the water is returned to the Ottawa River, its levels of bacteria, phosphorus and organics are far below all limits set by the plant's operating permit.  The E.coli count, for example, reaches only 14 per cent of the allowed amount.
  • Produces 39 dry tonnes of biosolids each day, which are used as agricultural fertilizer

The Wastewater Treatment Process

1.  Coarse Screening/Pumping

Wastewater flows to the plant through enormous pipes buried deep in the ground. Upon arrival, any object bigger than a shoe gets screened out. The sewage is then pumped to ground level. It flows through the rest of the treatment processes by gravity.

2.  Fine Screening/Degrit

Screens catch smaller objects like sticks and rags. Degrit tanks separate pebbles, grit and sand from the other solids that can be further treated. Screenings and grit are trucked to a landfill and buried.

3.  Primary Clarification

The plant has 15 covered settling tanks. Water is slowed down to allow heavy solids to sink to the bottom, while grease and fat float to the surface. The settled solids (sludge) and floatables (scum) are removed by skimmers and sent to digesters (step 9). The remaining water still contains very fine solids and dissolved material like sugar.

4.  Aeration

In these long and deep uncovered tanks, naturally occurring bacteria break down the small particles. Air is blown into the tanks, making bubbles. This creates ideal conditions for the bacteria and keeps the solids from settling.

5.  Phosphorus Removal

A solution of iron is added to the wastewater. Iron captures the phosphorus, creating a solid that can sink and be separated from the water.

6.  Secondary Clarification

16 round open tanks slow the wastewater down, allowing the remaining solids and bacteria to settle as sludge. Most of the sludge is continuously pumped back to the aeration tanks, so that the bacteria can biodegrade more waste. Excess sludge is further processed (step 9).

7.  Disinfection

Leaving the secondary clarifier, the water is disinfected by adding chlorine, the equivalent of strong household bleach. This kills the majority of microorganisms that have survived the treatment process.

8.  Dechlorination

A final chemical is added to remove excess chlorine. Now the treated water can be returned to the river.

9.  Biosolids Processing

Excess sludge and scum is treated in six sealed tanks (anaerobic digesters), using other naturally occurring bacteria. These bacteria convert about half of the sludge into methane gas, and carbon dioxide. The rest goes through centrifuges, where water is removed.  What is left is a nutrient-rich, soil-like material called biosolids. Farmers use it as a fertilizer.

10.  Cogeneration

The methane gas that has been produced in the anaerobic digesters is burned in engines and boilers, producing heat and electricity that is used to run the plant.

All About Sewers (activity book)

Learn more about Ottawa's sewers through fun games and puzzles in our downloadable activity book!