Seepage Pit vs Leach Field: How LA Hillside Septic Systems Work, and Signs of Trouble

Most septic systems in the Los Angeles hills send treated water from the tank into one of two places: a seepage pit or a leach field. Knowing which one you have explains a lot about how the system behaves and what fixing it involves.

How each one works

• Seepage pit: a deep, lined pit, often with a concrete cap, that lets liquid from the tank soak out through its walls into the surrounding soil. Pits take up little yard space, which is why they are common on steep or small hillside lots.
• Leach field: a set of shallow trenches with perforated pipe in gravel that spreads the liquid over a wider area of soil. Leach fields need more flat-ish yard, so they show up more on larger or gentler lots.

Both depend on the tank doing its job first. When solids get past the tank, they clog the pit walls or the trenches, and the soil stops taking water.

Signs the dispersal system is struggling

• Drains and toilets slow down across the house, not just one fixture.
• The tank fills back up faster than it should after pumping.
• Wet, soggy or unusually green ground over the pit or trenches.
• Sewage odor in the yard.
• Standing liquid in a seepage pit. Unlike a tank, a seepage pit should never be full of liquid.

How we find out what is wrong

We start by locating and opening the tank and the pit or field, then look at the liquid levels and the condition of the components. For seepage pits we can run a hydraulic test: a measured amount of water goes in, and we come back within 24 hours to see how much the pit took. That tells you how the pit is really performing.

Restore before you replace

A struggling system does not always need a new pit or field. Depending on what we find, options can include pumping and cleaning, repairing baffles or lines, adding risers for proper access, or treatment such as ORCA Pods, made by ORCA OWTS. We install and service ORCA Pods. When a pit or field really has reached the end of its life, replacement is designed by a qualified designer, permitted with the reviewing agency, and built to the approved plans.

As we tell clients, all of this work is usually cheaper than a new system, so it pays to look before you replace.

Know which agency reviews your lot

In unincorporated LA County, septic work is reviewed by County Environmental Health. Cities such as Malibu run their own programs. We confirm the agency for each address before pricing any repair.