Signs Your Septic System Is Failing

A septic system rarely fails overnight. Usually it sends signals for weeks or months: a drain that is a little slower, a smell on still evenings, grass that stays too green. Catching those signals early can mean the difference between a modest repair and a full drainfield replacement. This page lists the common signs, what they usually point to, and what to do.

Inside the house

Slow drains everywhere

One slow sink is usually a local clog. Every fixture draining slowly, especially the lowest ones, suggests the problem is downstream: the building sewer, the tank, or the drainfield.

Gurgling

Gurgling toilets or drains when water runs elsewhere in the house can mean air is being pushed through a partial blockage or that the tank's liquid level is higher than it should be.

Sewage backup in the lowest drain

A backup into a basement floor drain, lower-level shower or tub is the most urgent sign. Stop using water and call. If the tank's liquid level is normal, the blockage is likely between the house and the tank; if it is high, the problem is at the outlet or in the drainfield.

Outside

Odors

A sewage smell near the tank, the lids or over the drainfield can mean an overfull tank, an unsealed lid or effluent near the surface.

Wet or spongy ground

Soggy ground over the drainfield, particularly during dry weather, can mean effluent is not soaking in and is rising toward the surface.

Unusually green, lush stripes

Bright green grass in lines over the trenches during a dry Rogue Valley summer can indicate effluent near the surface.

Surfacing effluent

Standing liquid, dark staining or sewage odor at ground level means the system has failed at that point. Keep people and pets away.

Alarms and equipment

Pump and treatment systems have a high-water alarm. If it sounds, the pump may have failed, a float may be stuck, or too much water may be entering the tank. See what to do when a septic alarm goes off.

What a technician will check

1. The liquid level in the tank relative to the outlet. A high level suggests a problem at the outlet or in the drainfield.
2. Baffles and tees, especially the outlet. A missing outlet baffle lets scum into the drainfield.
3. The effluent filter, if fitted, which can clog and cause backups.
4. The distribution box or pump chamber.
5. The drainfield surface and, where needed, inspection ports or probes to check for ponding in trenches.

Is it the tank or the drainfield?

Pumping relieves symptoms caused by an overfull tank. If symptoms return quickly after pumping, the drainfield is often the issue. Some fields recover after the cause is fixed and they are rested; others need replacement under a DEQ repair permit. Our repair and drainfield page covers diagnosis, and the drainfield replacement cost guide covers budgeting.

What to do right now

• Cut water use sharply: delay laundry and dishwashing, take short showers.
• Keep vehicles and people off the drainfield.
• Do not open tank lids yourself; septic tanks contain hazardous gases.
• Skip additives. OSU Extension says they are not needed, and they do not fix a failing field.
• Write down when symptoms started and when the tank was last pumped. It speeds up diagnosis.

Oregon permit note

Repairing a failing system in Oregon generally requires a DEQ repair permit. DEQ's repair permit guide says emergency repairs can proceed first in some cases, with the permit application submitted within three working days.

Common questions