Septic systems

Most rural homes that aren’t on a sewer line treat their wastewater on site with a septic system. A conventional system has two parts: a septic tank and a drainfield, also called a leach field or soil absorption field.

How it works

All the water leaving the house runs down one main pipe into the tank. The tank is a buried, watertight box, usually concrete, fibreglass or polyethylene. It holds the wastewater long enough for solids to sink into a layer of sludge while oils and grease float up as scum. Baffles and a T-shaped outlet keep both layers inside the tank.

The liquid in the middle, called effluent, flows out to the drainfield. That’s a shallow, covered trench system in unsaturated soil, with perforated pipes or chambers that let the effluent seep out slowly. The soil does the real treatment: as the effluent trickles down, it filters out bacteria, viruses and nutrients before the water reaches groundwater.

If the drainfield gets more water than the soil can take, it floods. Sewage can then surface in the yard or back up into sinks and toilets.

Alternative systems

Where soil is too thin, too wet or too tight for a conventional drainfield, alternative systems use pumps or gravity to pass effluent through sand, peat, constructed wetlands or other media. Some evaporate or disinfect the water before it reaches the soil. These have more moving parts, so they need inspecting more often, and a service contract matters more.

Keeping it working

Upkeep comes down to four habits:

1. Inspect and pump on schedule. How often depends on household size, how much water you use, how many solids go in, and the tank’s size. Keep a record of the sludge and scum levels at each visit, so you know when the next pump-out is due.
2. Use less water. Every gallon used indoors goes through the tank. Efficient toilets (1.6 gallons a flush or less, against 3.5 to 5 in older ones), aerators and full laundry loads all help. Spreading laundry across the week gives the tank time to work.
3. Only human waste and toilet paper. Never flush wipes, grease, coffee grounds, cat litter, medicines or household chemicals. Skip chemical drain openers and limit the garbage disposal.
4. Protect the drainfield. Don’t park or drive on it. Plant trees far enough away that roots can’t reach the pipes, and send roof drains and sump pumps elsewhere.

For a Leafhouse project

A septic system is usually the default for a rural home, and the county health department will want a soil evaluation before it issues a permit. That makes the soil one of the first things to check on any piece of land. If a site can’t take a conventional drainfield, the options are an engineered alternative system or cutting the wastewater load with a composting toilet, which still leaves greywater to deal with.