Sourced from EPA SepticSmart guidance and OWTS Policy Section 11 — last checked August 2026.
Are Your Symptoms Urgent?
Check off anything you’re noticing. Not a diagnosis — a quick read on how soon to act.
General guidance only. If sewage is backing up inside your home, stop using water and call a licensed provider right away.
The Four Official Indicators
Most states leave “failing” to interpretation. California doesn’t. Under Section 11 of the OWTS Policy, a system requiring corrective action is indicated by:
| Indicator | What it looks like |
|---|---|
| Surfacing effluent | Wastewater appearing at ground level over the leach field or tank |
| Backing up in fixtures | Sewage coming back up through drains, tubs or toilets |
| Structural failure | A collapsed or broken tank, lid, riser or pipe |
| Water degradation | Significant groundwater or surface water contamination attributable to the system |
Knowing this list is useful, because it tells you where the line is. A slow drain is a maintenance issue. Surfacing effluent is a regulatory one.
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What Each Symptom Means
Sewage backing into fixtures is the most urgent. Stop running water and call a professional.
Multiple slow drains at once points at the system rather than the plumbing. One slow sink is a clog; every fixture slowing together is the system struggling.
Outdoor odor means gases are escaping where they shouldn’t.
Soggy ground over the leach field means the soil isn’t accepting effluent.
Unusually green grass over the field means nutrient-rich effluent is reaching the root zone.
An alarm on a treatment unit means a component isn’t performing. On a Tier 3 system that matters more than usual, because the permit depends on the unit meeting a standard.
Check the Effluent Filter First
Before assuming the worst, because it’s the cheapest explanation.
If your system has an effluent filter, its job is stopping solids reaching the leach field. When it clogs, effluent backs up — producing slow drains throughout the house that look exactly like field failure.
Cleaning a filter costs a fraction of a field replacement.
Rain vs. Failure in California
California rain arrives concentrated, which creates two ways to misread a system.
Rain can mimic failure. When soil is fully saturated the field genuinely can’t accept effluent. That’s physics. If the area dries at roughly the same rate as the rest of the yard, it was weather.
Rain can mask failure. A genuinely failing system may look no worse than surrounding ground during a wet stretch, becoming obvious only in the dry season.
The test is comparison and persistence. Is the field area wetter than the rest of the yard? Does it stay wet noticeably longer? Is there odor? Wet ground plus odor is not weather.
After a Wildfire
Worth its own section in California.
If a property has burned over, have the system inspected before assuming it’s intact. Heat damages risers, lids and shallow piping, and plastic components are vulnerable.
Post-fire erosion is the underrated risk. Vegetation loss changes how water moves across a slope, and a leach field that drained fine before can end up receiving concentrated runoff after the first significant rain.
Heavy equipment from fire response or debris removal shouldn’t have driven over the leach field. If it did, compaction damage is a real possibility.
After a Long Dry Spell
Extended drought causes some California soils to shrink and crack, which can stress pipe joints and connections. New slow drains appearing after a long dry period are worth investigating rather than dismissing.
What to Do
For anything beyond a single slow drain, get a professional evaluation.
And if a replacement turns out to be needed, establish the tier before assuming it’ll be a like-for-like swap. Near listed water, it may not be.
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Frequently Asked Questions
What are the official signs of a failing septic system in California?
The OWTS Policy names four in Section 11: surfacing effluent, wastewater backing up in plumbing fixtures, structural failure of a component or pipe, and significant groundwater or surface water degradation.
What should I check first if drains are slow?
The effluent filter, if your system has one. A clogged filter causes slow drains throughout the house that look exactly like leach field failure, and cleaning it costs a fraction of a replacement.
Is soggy ground always a problem?
Not always. California rain arrives concentrated and saturated soil genuinely cannot accept effluent. The test is whether the field area is wetter than the rest of the yard and stays wet longer, and whether there is odor.
What should I look for after a wildfire?
Damage to risers, lids and shallow piping from heat, post-fire erosion sending concentrated runoff across the leach field, and compaction if heavy equipment drove over it during response or debris removal.