Caring for your drainfield

The drainfield is where your wastewater actually gets treated, by soil and the microbes living in it. The tank protects the drainfield by keeping solids back. Nothing protects the drainfield from what happens on the surface except you. Here's how to look after it.

Keep the weight off

EPA's first rule for the drainfield is to never park or drive on it. The weight of cars, trucks, and equipment compacts the soil and can crush pipes. Compacted soil can't absorb effluent. Don't build on it either: no sheds, patios, pools, or play sets. Keep livestock off it too.

Plant the right things

Grass is the best cover. It holds the soil, uses some of the water, and lets air in. EPA advises planting trees an appropriate distance from the drainfield so roots don't grow into the pipes. A septic professional or the county can tell you how far that is for the species you have in mind. Avoid vegetable gardens directly over the drainfield.

Keep extra water away

The drainfield can only absorb so much. EPA recommends keeping roof drains, sump pumps, and other rainwater drainage away from it, because extra water slows or stops the wastewater treatment process. Check where your downspouts discharge, and grade the ground so surface water runs away from the drainfield.

Inside the house, the same idea applies. Spread laundry across the week, fix leaks, and don't drain a hot tub or pool into the system. See saving water on septic.

Keep solids out

Solids escaping from the tank are the other big threat. Penn State Extension explains that as a tank fills, solids get carried out to the absorption area. There they help form a biomat that clogs the soil. An effluent filter on the tank outlet helps, but the real protection is pumping before the tank is too full. Start with our pumping calculator and confirm with inspections.

Let it rest

Penn State research found that drainfields benefit from periodic resting. Penn State suggests one practical trick: schedule the pump-out for the day before the family leaves on vacation, so the soil can dry out and any biomat can break down while the house is empty. Some systems have two drainfields and a diversion valve so one can rest while the other works. If yours does, ask your provider how often to switch.

Signs the drainfield is struggling

Soggy ground, sewage smells, bright green stripes of grass, or slow drains throughout the house can all mean the drainfield is overloaded or clogged. See signs your septic system is failing for what to do.

And protect your well

EPA explains that effluent from the drainfield eventually reaches groundwater. If a drinking water well is in the path of that groundwater flow, especially a shallow well in sandy soil, it's at greater risk. A healthy drainfield that treats effluent properly is part of protecting your water. See protecting your well from your septic system.

What the drainfield actually does

EPA describes the drainfield as a shallow, covered excavation in unsaturated soil. Pretreated wastewater from the tank flows through piping onto porous surfaces and filters down through the soil. The soil accepts, treats and disperses the wastewater, removing harmful coliform bacteria, viruses and nutrients before it reaches groundwater. If the drainfield is overloaded with liquid, it can flood. Sewage then comes to the surface or backs up into toilets and sinks.

That's why nearly every drainfield rule comes down to one of three things: keep the soil uncompacted, keep it from being flooded, and keep solids from reaching it.

Water use and the drainfield

EPA notes that average indoor water use in a single-family home can be as much as 70 gallons per person per day, and a single leaky or running toilet can add as much as 200 gallons a day. All of it ends up in the drainfield. Practical steps:

• Fix running toilets and dripping faucets right away. They're the most common hidden load.
• Spread out laundry. EPA warns that doing all the household laundry in one day doesn't give the tank time to treat waste and can flood the drainfield.
• Choose efficient fixtures. EPA says high-efficiency toilets use 1.6 gallons per flush or less, compared with 3.5 to 5 gallons in many older homes.
• Don't connect water softener backwash, sump pumps or roof drains to the septic system unless your system was designed for them and local rules allow it.

What should never go down the drain

EPA's "never flush" list protects the tank and drainfield from solids and chemicals. It includes cooking grease or oil, non-flushable wipes, feminine hygiene products, diapers, dental floss, cigarette butts, coffee grounds, cat litter, paper towels, pharmaceuticals, and household chemicals such as gasoline, oil, pesticides, antifreeze and paint. Grease and wipes are especially damaging, because they float past the tank's baffles or clog the outlet and end up sealing the soil.

Seasonal care

• Spring: look for soggy spots or odors after snowmelt, and check that downspouts drain away from the field.
• Summer: keep irrigation sprinklers off the drainfield.
• Fall: rake leaves but don't pile them on the field. Avoid heavy equipment when the ground is wet.
• Winter: in cold climates, a layer of grass or mulch helps insulate the field. Don't let vehicles compact snow over it, since compacted snow drives frost deeper.

Maintenance that protects the field

EPA recommends inspecting the system at least every three years and pumping the tank about every three to five years. Ask your provider about an effluent filter on the tank outlet. It helps keep solids out of the drainfield and needs periodic cleaning.

Key takeaways

• Never drive, park or build on the drainfield.
• Keep extra water off the field, both from inside the house and from the yard.
• Keep grease, wipes and chemicals out of the system.
• Pump and inspect on schedule so solids don't reach the soil.