7 Signs Your Septic System Is Failing
For homeowners in Woodside, Portola Valley, Los Altos Hills, and the Bay Area and Peninsula hills
Septic systems fail slowly, then suddenly. Catching the early signs can be the difference between a manageable repair and an emergency replacement with sewage on the lawn. Here is what to watch for.
1. Slow drains throughout the house
One slow sink is a plumbing problem. Every fixture draining slowly, especially the lowest ones in the house, points to the septic system.
2. Gurgling sounds in the pipes
Gurgling after you flush or run the washing machine means air is being pulled through water that has nowhere to go.
3. Sewage odors, inside or outside
A working system is odorless. Persistent smells near drains, the tank lid, or out over the leach field mean something is wrong.
4. Wet or spongy ground over the leach field
Standing water or unusually lush, bright green grass over the field, particularly in dry months, means effluent is surfacing instead of absorbing. This is the classic sign of a failed field.
5. Backups into tubs and toilets
Sewage backing up into the lowest fixtures in the house is the system telling you it is full and the field is not taking water. Treat this as urgent.
6. The tank needs pumping more and more often
If you have gone from pumping every three to five years to pumping every few months, the field is no longer doing its job. Pumping at that point is a band-aid, not a fix.
7. High nitrate readings or a failed inspection
Well water tests showing nitrates, or a failed septic inspection during a home sale, are formal red flags that county health officials take seriously.
What to Do Next
If you recognize one of these signs, get an on-site evaluation before it escalates. An honest local professional will tell you whether a repair is enough or whether the system has reached the end of its life, and what either path costs. See our 2026 cost guide for the Bay Area and Peninsula hills.