Short answer
The signs of septic system failure are sewage backing up into drains, slow drains, gurgling pipes, sewage odor near the tank or drainfield, and wet ground or unusually lush, bright green grass over the drainfield. Any one is a reason to call a septic professional. It does not prove failure. Avoid contact with sewage and do not open the tank.
Septic tank problems often start quietly. A drain that is a little slow, a smell by the tank, a patch of grass that is greener than the rest of the lawn. This guide describes the common warning signs of septic system failure, what each can mean in general terms, what to do right away, what usually causes failures, and what a professional checks.
A sign is a reason to get the system looked at, not a diagnosis. EPA's page on resolving malfunctions notes that it is not possible to diagnose the exact cause of an odor remotely, and the same goes for most signs. The aim here is to help you notice early and describe it well.
The warning signs, and what each can mean
These signs come from the EPA's pages on what to do if your septic system fails and its homebuyer guide. The right column is general, not a diagnosis.
| Sign | What it can point to |
|---|---|
| Sewage backing up into toilets, sinks or tubs | Wastewater is not draining away as it should. Causes can include a blockage or an overloaded drainfield. EPA says an overloaded drainfield can flood and cause backups. |
| Slow-draining sinks, showers and tubs | A clog in a pipe, a problem in the tank or an overloaded drainfield. One drain may be a local clog, so note how many are affected. |
| Gurgling sounds in the plumbing | EPA lists it as a warning sign. It often shows up together with slow drains. |
| Sewage odor near the tank or drainfield | Needs a professional on site. EPA says the cause of an odor cannot be diagnosed remotely. |
| Wet ground or standing water near the tank or drainfield | Wastewater may be reaching the surface or the drainfield may be saturated. |
| Bright green, spongy or unusually lush grass over the drainfield, especially in dry weather | EPA lists this as a warning sign. A professional can tell whether wastewater is reaching the soil near the surface. |
EPA also lists algae blooms in nearby water and high nitrate or coliform levels in water sources as signs that a system may be failing. If you have a private well, ask your health department about testing, since contaminated water can come from more than one source.
Slow drains and gurgling
Slow drains and gurgling are the most common early signs and the easiest to dismiss. They are also common with ordinary household clogs. A useful first step is to notice where it happens. If one sink is slow and everything else is fine, that points toward that pipe. If several fixtures slow down together, or the slow drains come with gurgling or odor, tell a septic professional. Our guide to clogged drains: DIY or call a plumber covers ordinary clogs, and tree roots in sewer lines covers one common cause of repeated slow drains.
The reason to act early is cost and damage. EPA says skipped pumping can let solids migrate into the drainfield and clog the system, and its 2017 homebuyer guide says repairing or replacing a system can cost thousands to tens of thousands of dollars.
Septic smell in yard
A septic smell in the yard is another reason to call. EPA's homebuyer guide lists a strong odor around the septic tank or drainfield as a warning sign and says to call a septic service provider immediately. EPA also says an odor cannot be diagnosed remotely. It could be a damaged cover, a vent, a wet drainfield or something else, and a professional has to look. Do not open the tank to find the source. If the smell is inside the house, call a plumber or septic professional and tell them where you notice it.
Wet spots and green grass over the drainfield
The drainfield is meant to take effluent into the soil below the surface. When the ground over it is wet, spongy or unusually green in dry weather, the soil may be overloaded. EPA lists unusually lush grass and wet ground near the tank or drainfield as warning signs. Take photos with the date. Keep people and pets off wet areas and do not drive or park on the drainfield. EPA says drainfields are not designed to handle vehicles or heavy equipment.
Septic tank backing up: what to do first
If sewage is coming up in the house, treat it as an emergency.
- Stop adding water. Avoid showers, laundry, the dishwasher and flushing as much as you can. EPA notes that being conservative with water reduces the load on the system.
- Avoid contact with sewage. EPA says sewage may contain harmful pathogens. Keep children and pets away.
- Call a septic professional. Say it is a backup. EPA's failure page also says to contact your local health department or regulatory agency for guidance.
- Do not open the tank. The Montana Department of Environmental Quality guide says gases inside pump chambers are poisonous and the lack of oxygen can be fatal, and tells owners not to enter. Treat every tank and chamber the same way and leave access covers closed.
- Do not add chemicals or additives. University of Maryland Extension says additives do not improve performance and some can send solids into the drainfield.
- Take notes and photos of what happened and when, for the company and the health department.
- Clean up carefully. EPA describes using protective clothing, washing the tools and clothing used, disinfecting the area and letting it dry for at least 24 hours. Follow your local health department's guidance.
If it is a smaller problem, such as slow drains, still reduce water use and book a visit soon. If your alarm is going off at the same time, read septic alarm troubleshooting.
What causes septic systems to fail
EPA says most septic systems malfunction because of inappropriate design or poor maintenance, and that poor soils, steep slopes and high groundwater can also cause failures. In everyday terms:
- Neglected pumping. If the tank is not pumped, EPA says solids can move into the drainfield and clog it. EPA suggests pumping every 3 to 5 years, depending on tank size, household size, water use and solids.
- Too much water. Large amounts of water in a short period, leaks, and rain or irrigation water on the drainfield can overload the system. EPA suggests spreading laundry over the week. University of Maryland Extension says leaking toilets and sinks can overload it and recommends directing rainwater and hot tub water away from the drainfield.
- Flushing the wrong things. EPA's homebuyer guide lists diapers, baby wipes, cat litter, cigarettes, coffee grounds, grease and feminine hygiene products as things that can clog the system, and household chemicals, gasoline, oil, pesticides, antifreeze and paint as things that can kill the microbes that treat the waste.
- Garbage disposals. EPA suggests eliminating or limiting use, since fats, grease and solids can clog the drainfield.
- Vehicles and heavy loads. EPA says to keep cars and anything heavier than a lawnmower off the drainfield. University of Maryland Extension adds that this can crush pipes or compact the soil.
- Roots. EPA says to plant trees away from the drainfield because roots can clog the field and cause failure.
- Age. EPA's homebuyer guide gives an average lifespan of 15 to 40 years, longer with good care.
- Site and design. A system that was not suited to the soil or the household may struggle. See types of septic systems.
What professionals check
According to EPA, an inspection normally covers the system's records and history, the tanks, and the drainfield. The inspector opens and checks all tanks (the septic tank, any pump tank and the distribution box), looks at sludge and scum levels, and looks for leakage and backup. EPA's homebuyer guide adds signs of backup such as staining above the outlet pipe, the integrity of the tank and its inlet and outlet pipes, and the drainfield for signs of failure like standing water. A camera may be used on pipes, and parts of the drainfield may be excavated. The inspector also checks pipes and electrical connections.
Ask for a written report that records what was found and what was done. Treat a recommendation for a big repair or replacement carefully: ask for the diagnosis in writing, and consider a second opinion, as described in our guide to septic contractors near me.
Why records help
EPA tells owners to keep maintenance records, and says inspectors review the permit, design and installation records, the age of the system, and pumping and maintenance records. Good records let a professional see how fast sludge builds up, when the last service was done, and what the tank size and layout are. Keep these together: the as-built drawing and permit from the health department, pumping receipts and service reports, notes on sludge and scum levels, any alarm events and dates, and photos of problems. When something goes wrong you can describe it quickly and avoid paying for the same discovery twice.
Prevention and cost pages
The cheapest septic repair is the one you avoid. The EPA recommends regular inspection and pumping, careful water use and protecting the drainfield. For what pumping and service typically involve and what changes the price, see septic tank pumping cost, septic tank cleaning cost and septic maintenance near me. For finding a company to call, use septic pumping near me.
What to look up where you live
EPA says it does not regulate single-family home septic systems, and in most states local health departments issue construction and operating permits. Look up:
- County or local health department, or environmental health office. Your permit and as-built drawing, whether a repair needs a permit, and what to do about sewage on the ground.
- State environmental or health agency. State rules on repairs, failing systems and service providers.
- State licensing board. Whether the person doing repairs must be licensed or certified.
Note for Canadian readers. Provinces and territories regulate onsite wastewater, often with municipalities or regional health units. Start with your municipality or health unit and your provincial ministry, and check the current rules for your province.
For septic, plumbing and drain company owners
Homeowners type their symptoms into Google before they ever look for a company name, and the companies that answer clearly are the ones they call. See the septic and drain marketing checklist and the guide to near me searches for plumbers and septic companies, or book a free call.
