If about 60% of New Hampshire homes are on septic, it's worth understanding what's actually happening underground. No jargon — just the parts and the path your wastewater takes.
Wastewater from your home flows to a buried septic tank, where solids settle out. The liquid in the middle flows on to a leach field — a network of perforated pipes in gravel or chambers — where it soaks down through the soil, which naturally filters and treats it before it rejoins the groundwater. That groundwater is the same water that feeds wells and, around here, the lakes. That's why keeping a system healthy matters beyond your own property.
Everything from sinks, toilets, showers, and laundry drains to one main pipe leaving the house.
Solids sink to the bottom as sludge; grease floats to the top as scum. The clearer liquid in between moves on.
Liquid flows into perforated pipes and trickles down through the soil, which filters and treats it naturally.
Modern NH tanks have two chambers. The design gives solids time to settle and keeps them from flowing out with the liquid. Bacteria in the tank break down some of the waste. An outlet filter (on newer systems) catches stray solids before they can reach and clog the leach field. This separation is the whole job of the tank — and it only works if the sludge and scum layers are pumped out before they build up too far.
The leach field is where treatment really happens. As liquid percolates down, the soil acts as a living filter, removing bacteria and nutrients before the water reaches the groundwater table. A cross-section, top to bottom:
This is also why setbacks exist: NH rules keep the field a required distance from wells and surface water (generally 75 feet for a typical home) so treated water has room to filter before reaching a drinking source or a lake.
Two failures are most common: the tank isn't pumped, so solids escape and clog the field; or the field is overloaded with water or damaged by traffic and stops absorbing. Both are largely preventable with routine pumping and sensible habits — which is the entire point of maintenance.
Call and we'll connect you with a licensed local pro who can take a look.