Septic backup in the house: what to do and cleanup

What is happening

A septic system has two main parts. Waste water from the house flows to a buried tank, where solids settle and are partly broken down. The liquid then flows out to a leaching bed, a set of perforated pipes in the soil, where it soaks away and is treated by the ground.

When the tank is full, the outlet is blocked or the bed cannot absorb any more, waste water has nowhere to go. It backs up the pipe and comes out at the lowest fixture in the house: usually a basement floor drain, shower or toilet.

The first few minutes

1. Stop using water. No flushing, taps, showers, laundry or dishwasher. Every litre you send down comes back up.
2. Keep everyone away, especially children and pets.
3. Switch off power to the affected area if water is near outlets or appliances and you can reach the panel safely.
4. Call a licensed septic pumping company. Ask for an emergency pump-out and for the cause to be checked.
5. Photograph the damage.
6. Call your insurer or broker.
7. Do not use the household vacuum, and do not run the furnace fan if sewage is near return vents.

Warning signs beforehand

Septic systems usually give notice:

• Drains throughout the house running slowly
• Gurgling in pipes and toilets
• Sewage smells indoors or over the tank and bed
• Wet, spongy ground or unusually green grass over the bed
• Sewage surfacing in the yard
• An alarm sounding, on systems with a pump chamber

Act on these and a backup can often be avoided.

Common causes

• The tank is overdue for pumping. Solids build up until they block the outlet or carry over into the bed.
• A clogged effluent filter at the tank outlet. Many newer tanks have one, and it needs periodic cleaning.
• A blockage between the house and the tank, from wipes, grease, roots or a collapsed pipe.
• A saturated bed after heavy rain, a high water table or the spring thaw. The system works again when the ground drains, but repeated saturation damages it.
• A failed bed. The soil has clogged after years of use or solids carry-over, or the pipes have been crushed by vehicles.
• A failed pump or float in systems that pump effluent up to the bed.
• Too much water at once: several loads of laundry in a day, a running toilet, or a house full of guests.
• Frozen pipes or bed in a cold winter with little snow cover.

Pumping is not the whole fix

A pump-out empties the tank and lets the house drain again. If the cause was simply an overdue tank, that may be the end of it. If the bed has failed or a pipe is blocked, the tank will fill and back up again within days or weeks. Ask the pumper what they found: the level in the tank before pumping, whether liquid ran back from the bed, and the condition of the baffles and filter.

In Ontario, on-site sewage systems are regulated under the Building Code. Repairs to or replacement of a tank or bed need a permit from the local authority, which may be the municipality, the health unit or the conservation authority depending on where you live.

Is it dangerous?

Yes. Septic waste is raw sewage. It carries bacteria, viruses and parasites that cause illness through contact or by hand to mouth.

• Wear waterproof boots, gloves and eye protection
• Keep cuts covered
• Wash thoroughly afterwards and launder clothing separately in hot water
• Throw out food, medicine and cosmetics that were touched
• Never enter or lean into a septic tank. The gases inside can kill.

How the cleanup is done

Extraction. Standing sewage is pumped or vacuumed out and disposed of properly.

Removal of porous materials. Carpet, underpad, drywall and insulation that sewage reached, baseboards, particleboard furniture, mattresses, cardboard and soft toys cannot be reliably cleaned. They are bagged and removed. Drywall is cut above the highest point the water wicked to.

Cleaning. Concrete, framing and other hard surfaces are washed with detergent to remove soil. Disinfectant does not work through dirt.

Disinfection. A suitable disinfectant is applied and left for its full contact time.

Drying. Dehumidifiers and air movers run until moisture readings in the structure are normal.

Contents. Hard, non-porous items can be cleaned and disinfected. Washable fabrics that had limited contact can go through a hot wash. Anything doubtful is discarded.

Rebuild after the septic problem is fixed, not before.

A small spill on bare concrete can be handled by a careful homeowner. A backup that reached finished rooms, carpet or stored belongings is a job for a contractor equipped for sewage.

Outside

Sewage that surfaced in the yard should be kept away from people and pets. Rope off the area. Sunlight and time reduce the contamination. Do not hose it towards a well, ditch or watercourse. If you have a well, have the water tested, and use another source in the meantime if there is any chance of contamination. Your local health unit can advise on testing.

Insurance

Sewer backup coverage is an optional endorsement on home policies. Whether it responds to a septic backup depends on the wording. Some include septic systems and some limit or exclude them. The repair or replacement of the septic system itself is generally not covered, as it is treated as maintenance. Ask your broker how your policy treats a septic backup before you need to know.

Preventing the next one

• Have the tank inspected and pumped on a regular schedule. Every three to five years is commonly recommended, depending on tank size and household.
• Clean the effluent filter as the installer recommends
• Spread laundry through the week
• Fix running toilets and dripping taps
• Flush only toilet paper. No wipes, sanitary products, grease, paint or solvents.
• Keep vehicles, sheds and paving off the tank and bed
• Keep trees and deep-rooted shrubs away from the bed
• Direct downspouts and sump discharge away from the bed
• Know where the tank and bed are, and keep the lids accessible

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