Septic questions, answered for Middle Tennessee.

Everything that goes down a drain flows to the septic tank. Solids sink to the bottom as sludge, grease and light material float as scum, and the clearer water in the middle flows out to the drain field, where the soil finishes treating it.

Baffles or tees at the tank’s inlet and outlet keep the scum and sludge inside. The drain field is a set of perforated pipes in gravel or chambers that spread the water into the soil. Pumping removes the sludge and scum the tank can’t break down on its own.

A conventional system has three parts: the septic tank, the baffles (or tees and an outlet filter) that keep solids in the tank, and the drain field where the soil treats the water. Many systems also have a distribution box that splits the flow between field lines.

Some systems add a pump tank and alarm, which lift effluent uphill or dose it to the field, or an aerobic treatment unit that adds air to treat the water further.

A conventional system lets effluent flow by gravity from the tank into a trench drain field. An alternative system is any other design TDEC permits when the soil isn’t suited to conventional trenches, such as low-pressure pipe, drip or mound-type designs, or systems with pumps and treatment units.

In Middle Tennessee, shallow limestone, heavy clay and Highland Rim fragipans are common reasons a lot needs an alternative design. Alternative systems usually need more regular attention, especially pumps, floats and alarms.

A healthy septic tank already has the bacteria it needs from normal household use, and additives don’t replace pumping. Sludge still builds up and still has to be removed.

Some products can even stir up solids and push them into the drain field. The best things you can do for the bacteria are to keep harsh chemicals, medicines and heavy bleach use out of the tank.

A well-built, well-kept system can last for decades. Tanks often outlast drain fields; the field’s life depends mostly on whether solids and grease are kept out of it and whether it’s overloaded with water.

Pumping on schedule, fixing running toilets and keeping vehicles off the field are what make the difference.

Most households should have the tank pumped every three to five years. A smaller tank, more people in the house, a garbage disposal or a home business can mean every two or three years.

The right interval depends on tank size and how the house is used. If you don’t know when it was last pumped, pump it now and use what we find to set the schedule.

The TDEC permit for your system usually lists the tank size. Tennessee sizes tanks by the number of bedrooms, so newer homes generally have larger tanks than older ones.

If there’s no permit record, we can tell a lot when the tank is open and pumped.

Only toilet paper and human waste belong in the toilet. Keep out wipes (even “flushable” ones), paper towels, feminine products, condoms, dental floss, cat litter, cigarette butts and medications.

At the sink, keep out cooking grease and oil, coffee grounds, paint, solvents and harsh chemicals. Go easy on the garbage disposal, which adds solids fast.

It works, but it fills the tank faster. Food scraps add solids that settle as sludge, so a house with a disposal usually needs pumping more often.

Scraping plates into the trash or a compost pile is easier on the system.

Large amounts of water at once can. Doing six loads on a Saturday sends a surge through the tank that can push solids into the field and flood it, especially in clay or wet seasons.

Spread laundry through the week, use a lint filter on the washer discharge if you can, and avoid powdered detergents that don’t dissolve well.

Risers bring the tank lids up to the surface, so the tank can be found and opened without digging every time. On tanks that are pumped regularly they save time and lawn damage.

Lids at the surface must be secure and child-proof. Never leave a tank opening unattended or loosely covered.

Slow drains throughout the house, gurgling toilets, sewage odors outside, soggy ground or bright-green stripes over the drain field, and sewage backing up into the lowest drains are the common signs.

Catching it early, often with a pump-out and a check of the baffles and lines, can keep a small problem from becoming a new drain field.

Stop using water right away: no flushing, showers, laundry or dishwasher. Keep people and pets out of the area, because sewage is a health hazard, and call (615) 306-8706.

Don’t open the tank yourself. The cause might be a clogged line, a full tank, a failed pump or a saturated field, and each one is handled differently.

A soggy, smelly field means effluent is coming to the surface instead of soaking into the soil. Common causes are solids that have clogged the field because the tank wasn’t pumped, too much water at once, a broken pipe, or soil that is saturated after heavy rain.

Keep people, pets and vehicles off the area and call. Surfacing effluent isn’t safe to touch.

On systems with a pump tank, the alarm means the water level is too high: the pump may have failed, a float may be stuck or the pump’s breaker may have tripped. Use as little water as you can and call.

Don’t open the pump tank or touch the control panel wiring; it’s live electrical equipment in a wet location. Most alarms have a silence button you can press while you wait.

No. Never enter a septic tank or lean into an open one. Septic gases such as hydrogen sulfide and methane, and the lack of oxygen, can kill within minutes, including people who try to rescue someone.

Keep lids secured, and keep children and pets away from an open tank. Inspection and repair inside tanks is work for trained crews with the right equipment, from outside the tank.

Gurgling usually means air is being pushed through water where it shouldn’t be: a partly blocked line, a full tank or a blocked plumbing vent. If every drain gurgles and runs slow, suspect the tank or the line to it.

A pump-out shows quickly whether the tank was the problem.

Because of the limestone. Much of Middle Tennessee has clay soils that weathered from limestone, and in many places the rock is only a few feet down. Clay drains slowly and shallow rock leaves little soil to treat effluent.

The limestone is also karst: water dissolves it into cracks, caves, springs and sinkholes. Effluent that reaches those cracks too quickly isn’t treated, which is why soil depth matters so much in TDEC’s evaluation.

Karst is limestone ground that has been dissolved by water over time, leaving sinkholes, springs and underground channels. Much of Middle Tennessee is karst country.

Water moves fast through karst. A drain field needs enough soil between the trenches and the rock to clean effluent before it reaches those channels, and sinkholes shouldn’t be used for drainage of any kind.

Sumner County sits on both. Its northern half is on the Highland Rim, with silty soils that often have a fragipan, a dense layer that slows water and can hold it near the surface in wet seasons. The southern half is in the Central Basin, with clay soils over limestone that can be shallow to rock.

Both can carry a working septic system, but they fail in different ways: Rim fields tend to go soggy in winter and spring, Basin fields tend to struggle in heavy clay and thin soil.

When the soil is already full of water, it can’t take effluent too. Clay and fragipan soils hold water a long time, so a field that’s fine in summer can back up in a wet Tennessee winter or spring.

Cut water use during wet spells, send gutters and downspouts away from the field, and keep the tank pumped so the field only gets clear water.

No building, paving, parking or driving over the drain field or tank. Weight crushes pipes and packs the soil so it can’t absorb water.

Grass is the best cover. Keep trees and big shrubs well away; roots go looking for the water in the lines.

Yes. A septic system is one of the most expensive parts of a rural home to replace, and you can’t see it. An inspection with the tank pumped shows the tank’s condition, the baffles, and signs of trouble in the field before you close.

Ask the seller for the TDEC permit and pumping records, and find out where the tank and field are before you make plans for the yard.

There isn’t a general statewide requirement for a septic inspection at the sale of a home, but lenders, buyers and some loan programs often ask for one. Check with your lender and agent early.

Tennessee sellers do have to disclose known defects, and since 2019 they must also disclose a known future obligation to connect to public sewer.

The Tennessee Department of Environment and Conservation (TDEC), Division of Water Resources. For Sumner, Wilson and Robertson counties that’s handled through TDEC’s Nashville Environmental Field Office.

A few Tennessee counties run their own programs under contract with the state, Davidson County among them, so north Nashville properties go through the county.

Yes. In Tennessee a permit is required to build, modify or repair a septic system. TDEC does a site and soil evaluation and inspects the work before it’s covered.

Pumping a tank doesn’t need a permit; the pumper needs one of their own.

Start with TDEC’s online search for septic tank permits, which has records for many permitted systems, often with a drawing of the layout. Your closing papers or the previous owner may have a copy.

Older systems may have no record. A cleanout pipe outside the house, a low or high spot in the yard, or a line of greener grass are clues, and we can locate the tank on site.

Yes. Tennessee sizes septic systems by the number of bedrooms. Adding a bedroom can mean the current permit no longer covers the house. Check with TDEC before you build.

Anyone who pumps septic tanks in Tennessee must hold a pumper permit from TDEC’s Division of Water Resources. TDEC publishes its permitted installers and pumpers in a searchable online viewer you can filter by county.

ABC Septic Services, LLC holds Tennessee septic pumper permit #949, listed under Sumner County.

Installers need a TDEC installer permit, which requires passing an exam; alternative systems need additional permitting. The system itself needs a TDEC construction permit before work starts.

Ask any installer which permit they hold and check it in TDEC’s installer and pumper viewer.

Ask whether they hold a TDEC permit for the work, what the price includes (locating, digging to lids, disposal), and whether they’ll check the baffles and tell you what they see.

Read reviews and ask neighbors. A good septic company explains what it found in plain words and doesn’t push work you don’t need.

Price depends on tank size, how easy the lids are to reach, whether they need to be dug up, and the distance. Call (615) 306-8706 for a straight price for your tank.

Yes. In its own words, ABC Septic Pumping Services is a “Professional, Local, Christian Family Owned Septic Pumping & Cleaning Service,” based in Bethpage in Sumner County.