Signs your septic system is failing

Septic systems usually warn you before they fail completely. The earlier you act, the more likely the fix is a pump-out or a cracked baffle rather than a new drainfield. Here are the signs EPA lists, roughly in the order homeowners notice them, with what each one often points to.

Inside the house

• Slow drains everywhere. One slow sink is usually a clog in that pipe. Several fixtures draining slowly at once point to the main line, the tank, or the drainfield.
• Gurgling in the plumbing. Air being pushed through water in the pipes can mean the line or tank is backing up.
• Sewage backing up into the lowest drains, such as a basement floor drain or a ground-floor shower. This needs attention the same day.

In the yard

• Standing water or damp, spongy spots over the tank or drainfield, especially when it hasn't rained.
• Sewage odors around the tank or drainfield.
• Bright green, lush grass over the drainfield, even in dry weather. Effluent is surfacing and fertilizing the grass.
• Algae blooms in a nearby pond or lake.

In the water

EPA also lists high levels of nitrates or coliform bacteria in drinking water wells as a sign of septic trouble, whether it's yours or a neighbor's. If your well test suddenly shows bacteria or rising nitrate, get the septic system checked as well as the well.

Not every smell means failure

EPA notes that odors can come from the plumbing vent on the roof, which is a normal part of the system. Vents can clog with leaves or freeze in a cold snap, and wind can push the smell down into the yard. A vent problem is a far cheaper fix than a failing system, so it's worth checking first.

What to do first

1. Cut water use right away. Hold off on laundry, long showers, and the dishwasher.
2. Call a licensed septic service provider to locate and inspect the tank. If it's full, pumping may give immediate relief. Ask them to check the baffles, the effluent filter, and the pipe to the drainfield.
3. Keep people and pets away from surfacing sewage, and avoid contact with it. It can carry harmful pathogens.
4. Call your local health department if sewage is surfacing or backing up. Repairs usually need a permit.

Why pumping doesn't always fix it

Penn State Extension explains that by the time sewage backs up into a house, the drainfield soil is often clogged with a nearly impermeable layer called a biomat. Pumping the tank won't remove it. Sometimes resting the drainfield lets the biomat break down. Other times the drainfield has to be repaired or replaced. The best protection is prevention: regular inspections and pumping, as EPA recommends. See our pumping calculator.

Common causes

EPA says most malfunctions come from inappropriate design or poor maintenance. That includes systems installed in unsuitable soil or where groundwater is high, tanks that were never pumped so solids migrated to the drainfield, too much water, and physical damage from vehicles or tree roots. Knowing the cause helps you avoid a repeat after repairs.

EPA's full list of warning signs

EPA lists these common signs of a failing septic system:

• water and sewage from toilets, drains and sinks backing up into the home;
• bathtubs, showers and sinks draining very slowly;
• gurgling sounds in the plumbing;
• standing water or damp spots near or over the tank or drainfield;
• sewage odors around the tank or drainfield;
• bright green, spongy, lush grass over the tank or drainfield, even in dry weather;
• algae blooms in nearby lakes or ponds;
• high levels of nitrate or coliform bacteria in drinking water wells.

Odor: normal or a problem?

EPA notes that not every odor means failure. A smell may come from the roof vent or another vent pipe that equalizes pressure in the system, which is a normal part of how it works. Vents can become obstructed, though, and odors can also come from a dry floor drain trap or a failed wax ring under a toilet. If the smell is outdoors near the tank or drainfield, or comes with wet ground, take it seriously.

Why systems fail

EPA says most septic systems malfunction because of inappropriate design or poor maintenance. Common causes:

• Skipped pumping. Solids migrate into the drainfield and clog it. EPA recommends pumping about every three to five years.
• Too much water. Leaks, big laundry days or roof drains flood the drainfield.
• Poor site conditions. Some systems sit in inadequate soils, on steep slopes or above high water tables, which can cause hydraulic failure.
• Physical damage from vehicles, construction or tree roots.
• Harmful materials such as grease, wipes or chemicals.

Who to call

EPA suggests contacting a local septic service provider, your local health department, or your onsite wastewater regulatory agency. EPA also mentions directories such as NOWRA's Septic Locator and the National Association of Wastewater Technicians. Repairs or replacements typically require a permit.

What not to do

• Don't keep using water heavily in the hope that it will clear.
• Don't pour in additives or chemicals as a fix. See septic tank additives.
• Don't dig or drive on a soggy drainfield.
• Don't let children or pets play near surfacing sewage.

Protecting your health

Sewage contains pathogens. If you see surfacing effluent, keep people and animals away, and test your well, because EPA lists high nitrate or coliform in wells as a sign of failure. Use bottled water until results come back clean.

Key takeaways

• Backups, slow drains, wet spots, odors and lush green stripes are classic signs.
• Not every odor means failure, so check vents and traps too.
• Cut water use and call a professional right away.
• Test your well if your septic system shows signs of failure.

Frequently asked questions

Will pumping the tank fix a soggy drainfield? It may give temporary relief, but if the drainfield itself is clogged or flooded, it needs a professional diagnosis.