A septic system treats household wastewater on your own property. Everything you flush or drain flows into an underground tank, where solids sink to the bottom and grease floats to the top. The partly treated liquid in the middle flows out to a leach field, also called a drain field, where the soil finishes the treatment. The tank holds back the solids, which is why it has to be pumped every few years.
The three main parts
- The building drain. One main pipe carries wastewater from every toilet, sink, shower and appliance out of the house.
- The septic tank. A buried, watertight tank, usually concrete, fibreglass or polyethylene, holds the wastewater long enough for the solids to separate out.
- The leach field. A network of perforated pipes in gravel-lined trenches or beds lets the liquid soak into the soil.
Some systems add a pump chamber or a treatment unit between the tank and the field. More on those below.
What happens inside the tank
Wastewater entering the tank slows down and separates into three layers:
- Sludge: heavy solids that sink to the bottom
- Scum: grease, oils and light material that float to the top
- Effluent: the clearer liquid in between
Baffles or tees at the inlet and outlet keep the scum and sludge inside the tank so only effluent flows out to the field. Many tanks also have an effluent filter at the outlet to catch fine solids. The filter needs regular cleaning, and our crew cleans it at each pump-out.
Bacteria living in the tank break down part of the solids without oxygen. They can’t break down everything, so sludge and scum slowly build up. Pumping removes them before they spill over into the leach field. Here’s how often your tank needs pumping.
How the leach field works
Effluent leaves the tank and flows to the leach field, either by gravity through a distribution box or under pressure from a pump. The perforated pipes spread it through gravel and into the soil, where natural bacteria break down organic matter and remove harmful organisms before the water reaches the groundwater.
The soil can only do that job if it has air and isn’t waterlogged. That’s why a leach field needs:
- No vehicles, sheds, decks or hot tubs on top of it
- Grass rather than trees or shrubs, whose roots can grow into the pipes
- Roof, sump and surface water directed away from it
- A tank that’s pumped on schedule, so solids never reach it
Signs that a leach field is struggling include soggy ground or standing water over it, a strip of unusually green grass, sewage odours outdoors, and drains that slow down or back up even after the tank has been pumped. A failing field is a job for a septic installer.
Common types of septic systems in the Okanagan
The right design depends on the lot, the soil and the slope, so neighbouring homes can have very different systems.
Conventional gravity system
The simplest setup. Wastewater flows downhill from the house to the tank and on to the leach field without a pump.
Pressure distribution system
Many Okanagan properties have some rise or slope, and many systems use a pump chamber after the septic tank. The pump stores effluent and sends it to the whole field at once in measured doses through smaller pipes. Because no part of the field stays saturated, the soil can drain and dry between doses. Raised systems such as sand mounds need a pump to work.
Treatment systems
Where the lot is small or the soil can’t treat effluent well, a treatment unit adds oxygen so aerobic bacteria break down waste more completely before it reaches the field. Some systems add a final filter, such as sand or peat, or a disinfection step. These systems need regular servicing by the company that maintains them, and their tanks still need pumping.
If you’re not sure what you have, your property records or the original installer can tell you.
Who looks after what
A septic system involves a few different trades. A septic installer designs, builds and repairs systems, including leach fields. A plumber looks after the pipes inside the house and leading out of it. A septic pumping company empties the tank, cleans the effluent filter and hauls the waste away.
D&L Environmental pumps residential and commercial septic tanks and treatment facilities from Vernon to Peachland. We clean effluent filters at pump-out and can add risers so your tank is easier to reach. We don’t install or repair septic systems, but each time we pump a tank we look it over and tell you about anything we can see that needs attention. Request service online, call 250-765-0999, or read about our septic tank pumping service.
Frequently asked questions
A leach field, or drain field, is the part of a septic system that disperses liquid from the tank into the soil through perforated pipes in gravel trenches. The soil then treats the water naturally.
Many Okanagan systems do. Pressure distribution systems and raised systems such as sand mounds use a pump to send effluent to the whole field in doses. A simple gravity system doesn’t need one.
No. The bacteria a tank needs arrive with normal household wastewater. Additives don’t replace pumping, because they don’t remove the solids that build up.
No. Weight can crack the tank or crush the pipes, and anything built over the tank blocks access for pumping.