Signs of a Failing Septic System, and What to Do First

On this page 6 sections

1. 01Is it the pipe, the tank, or the field?
2. 02What to do this week
3. 03What not to do
4. 04Why systems fail
5. 05Repair or replace: what it usually costs
6. 06Your well after a septic failure: test it

The most common signs of a failing septic system are sewage backing up into the house, drains that are slow all over the house, gurgling pipes, wet or spongy ground over the tank or drainfield, a sewage smell outside, and a strip of grass that stays bright green even in dry weather. A positive coliform or rising nitrate result in your well can be a sign too. Most of these don’t tell you on their own whether the trouble is in the pipe, the tank or the drainfield, and that’s the first thing to find out, because the fixes range from clearing a line to replacing the field.

Below: a table of the nine signs the EPA lists and where each one most likely points, the one measurement that separates a tank problem from a field problem, what to do this week, what not to do, and what repair usually costs.

Is it the pipe, the tank, or the field?

Short answer: a sign tells you where to look; the liquid level in the tank tells you where the problem is. A septic professional can check it in one visit.

Every drain in your house runs into one pipe to the tank. The tank holds the solids back and sends the liquid to the drainfield, where the soil soaks it up and cleans it. A blockage or overload at any of those three points can show up as the same symptom in the house. Here are the EPA’s nine signs, with the part of the system each one most often points to:

About the slow drain: if only one sink is slow and the rest of the house drains fine, the septic system is an unlikely cause, because everything downstream of that sink is shared with every other drain. If every fixture is slow, look at the shared part: the house sewer, the tank or the field.

The decision tree: what the liquid level tells you

Montana State University Extension’s troubleshooting guide, adapted from a University of Wisconsin publication, starts every backup with one question: how high is the liquid in the tank? Normal is “a foot or so below the top of the tank.” The guide is from 2005, but the logic is the same as the EPA’s description of how a system works.

Liquid level normal, but the house drains back up or run slow, so the water isn’t reaching the tank:

• Blockage in the house sewer (the pipe from house to tank): tree roots, a broken section, or a line laid at the wrong slope. A professional clears it with a sewer cable through the cleanout. If roots got in, the joints need sealing afterward.
• Scum plugging the tank inlet: the tank needs pumping and the inlet baffle needs checking.
• A plugged vent: this mostly causes gurgling, sometimes a sewer smell indoors. Roof vents that are too small can freeze shut in winter. A plumber fixes it.

Liquid level above normal, so water reaches the tank but can’t leave it:

• Plugged tank outlet. In older tanks the outlet baffle can crumble or collapse, letting solids overflow into the outlet. The fix: pump the tank, clear the line, replace the baffle.
• Blocked line from tank to field: solids that overflowed from the tank, roots in pipe joints, or a crushed pipe (heavy vehicles over a shallow line can do it). Pump, clear, then repair.
• Clogged field. Then you’ll usually also see wetness or seepage over the field.

Wet, swampy ground over the field, with or without backups in the house, comes down to five causes in the same guide: a field too small for the house (common after an addition), a clogging mat that has built up in the soil over the years, a seasonal high water table in spring, solids carried over from a tank that was too full, and extra water from leaking faucets and toilets.

The EPA also notes that a drainfield older than 25 to 30 years often has a thicker biomat (the same clogging layer) and that it’s time to plan an upgrade. If your field is that old and showing these signs, age is a likely part of the story.

What to do this week

Short answer: use as little water as you can, keep people and pets away from wet spots, find your records, and get a septic professional to open the tank. Call your county health department before any repair.

1. Cut water use now. Every gallon you send down the drain goes to a field that can’t take it. Fix a running toilet or dripping faucet today: the EPA says one leaky toilet can add up to 200 gallons a day. Spread laundry over the week instead of doing it in one go; Georgia’s extension notes that a saturated field may not absorb several loads on a rainy day.
2. Stay off the wet area. Keep children, pets and vehicles off. The EPA’s advice for sewage is to avoid contact with it, since it may contain pathogens. Don’t drive or park on the tank or field at all.
3. If sewage came into the house, follow the EPA’s cleanup steps: avoid contact, call your local health department, wear long rubber gloves and a face shield, wash everything, disinfect with a mix of 9 parts water to 1 part household bleach, dry it fully, and keep the area unused for at least 24 hours after it’s dry.
4. Find your paperwork. The last pumping receipt, the permit or system drawing from the health department, and your tank’s location. Montana’s guide points out that a map of the tank and field keeps the lawn from being dug up needlessly. If you don’t know when the tank was last pumped, Georgia’s extension says to have it pumped.
5. Call a septic professional to open the tank, check the liquid level and look at the baffles and the effluent filter. Washington’s health department says a clogged effluent filter needs cleaning or replacing; without a filter, a clog at the outlet will probably mean pumping the tank to find and remove it. To find someone, the EPA points to the NOWRA Septic Locator, the National Association of Wastewater Technicians, and your local health department.
6. Call your county health department. In Georgia, repairs or changes to a septic system must be permitted and inspected by the health department, and Georgia’s extension says the department can send someone to help identify the problem and give you a list of state-certified contractors. Ask what your county requires before anyone starts digging. The National Environmental Services Center also runs a technical hotline: (304) 293-4191.
7. Test your well if you have one. See the last section.

What not to do

Short answer: don’t pour in additives or chemical cleaners, don’t keep running water into a soaked field, and don’t expect a pump-out alone to fix a dead field.

• Additives. The EPA says septic additives are generally unnecessary and can even harm the system. The Georgia Department of Public Health discourages them, and Georgia’s extension adds that they “do not eliminate or reduce the need to pump out the septic tank.”
• Chemical drain openers and solvents. Georgia’s extension warns that chemical solvents break solids into small particles that move on into the drainfield and clog the lines, and that acids can corrode concrete tanks and distribution boxes. For a slow drain, a cable (a plumber’s snake) clears the clog mechanically instead.
• More water. A full laundry day, a running toilet, roof drains or a sump pump aimed at the field: the EPA says to spread laundry over the week and keep roof drains and sump pumps away from the drainfield. A soaked field needs less water, not more.
• Pumping and hoping. Pumping empties the tank; it doesn’t dry the soil. If the field is clogged or saturated, the tank fills back up to the same high level as you keep using water. Pump to diagnose and to clear a blockage, then fix what the pumper finds.
• Driving or parking on the field, also not while you’re looking for the problem. Montana’s guide lists compaction from heavy equipment among the things an inspector looks for.
• Digging or rebuilding before you’ve talked to the county. In Georgia, every repair or change needs a health department permit and inspection; find out what your county requires first.

Why systems fail

Short answer: the EPA says most septic systems malfunction because of inappropriate design or poor maintenance. Some of that is in your hands, some of it isn’t.

Other sources give maintenance a bigger share. Georgia’s extension calls poor maintenance “the most common cause of septic system failure,” and Montana’s guide says improper maintenance is by far the most common reason for early failure. Ohio State Extension draws a useful line: a malfunctioning system was designed and installed properly but isn’t working as designed, and can usually be fixed fairly easily; a failed system was badly designed or installed, has been used improperly, or has reached the end of its life, and needs major renovation or replacement. Two causes no table should leave out: tree and shrub roots, which Georgia’s extension says can grow into the drain lines and even the tank, and age. For a field past 25 to 30 years, the EPA says to start planning for an upgrade before you are in an emergency situation.

Repair or replace: what it usually costs

Short answer: the EPA puts repairing or replacing a failing conventional system at $5,000 to $15,000, and alternative systems can cost more. A clogged line or a broken baffle costs far less; a new field on difficult soil costs more.

What the fix looks like depends on what the pumper and the county find:

What drives the price up, from the sources above: the system type your soil allows (a mound or an aerobic unit instead of a gravel field), the size the county requires for your house, permits and design work, and how much of the old system can be kept. The EPA’s range has no year attached on its page, so treat it as a yardstick, not a quote. The step-by-step of replacing a field is in drain field replacement, and the system types are compared in septic system types.

If public sewer runs near your house, Washington’s health department says a connection should be considered once a field has failed. For money, the same page points to low-interest loans or grants through some local health departments, the nonprofit lender Craft3, and a USDA home repair program for those who qualify. Ask your county what exists where you live.

For scale, the pumping side: the EPA puts routine pumping at $250 to $500 every three to five years. Thirty years of that costs at most what the cheapest repair in the EPA’s range costs. The numbers behind that are in septic tank care and what septic pumping costs.

Your well after a septic failure: test it

Short answer: if you have a private well, test it for total coliform, E. coli and nitrate as soon as you suspect a septic problem, and again after the repair.

A failing system can send wastewater into the ground your well draws from, and the EPA lists high nitrate or coliform in drinking water wells as one of the signs. At Penn State’s university lab, the Agriculture/Septic package (coliform, E. coli, pH, TDS and nitrate) costs $70; your state lab will have its own price. How to take the sample is in how to test your well water.

• If E. coli shows up, stop drinking the water untreated and call your county health department or sanitarian. Boil drinking water in the meantime: Montana State says for at least one minute, Texas’s guide says two minutes at a full boil. Next steps are in coliform or E. coli in your well.
• If nitrate is high, don’t boil: boiling doesn’t remove nitrate, it concentrates it, New Jersey’s health department warns. The EPA level is 10 mg/L nitrate as nitrogen. That’s the legal limit for public water systems. No one enforces it on your private well, but it’s the yardstick labs and health departments use. If someone in the house is pregnant or you have a baby on formula, talk to your doctor and the county. More in nitrate in well water.
• Retest after the repair and keep both results with your septic records. A clean result after the fix, and again at your yearly test, is how you know the problem stayed fixed.

Once the system is working again, the Septic Planner gives you a pumping interval for your tank and household, and a log to keep with the tank drawing.

Quick answers

What are the signs of a failing septic system?

The EPA lists sewage backing up into the house, slow drains, gurgling pipes, standing water or damp spots near the tank or drainfield, sewage odors, bright green spongy grass over the system even in dry weather, a pipe discharging wastewater on the ground, algae blooms in nearby water, and high nitrate or coliform in drinking water wells.

How can I tell if the problem is the tank or the drainfield?

Have a septic professional open the tank and look at the liquid level. Montana State University Extension's guide says a normal level is a foot or so below the top of the tank. If drains back up at a normal level, the blockage is between the house and the tank. If the level is above normal, the outlet, the line to the field, or the field itself is blocked.

Will pumping the septic tank fix a failing drainfield?

Not on its own. Pumping is the first step for a plugged outlet or a blocked line, but a clogged or saturated field still can't take the water. Washington's health department says a field saturated by too much water can sometimes be dried out and rehabilitated; otherwise it needs replacing.

Do septic additives fix a failing system?

No. The EPA says additives are generally unnecessary and can even harm the system, and Georgia's health department discourages them. They don't replace pumping.

How much does it cost to fix a failing septic system?

The EPA puts repairing or replacing a failing conventional system at $5,000 to $15,000. Alternative systems, such as mounds or aerobic units, can cost more.