Seepage Pit Drilling,
Repair & Replacement

A seepage pit is a deep, lined hole that lets wastewater from the septic tank soak into the soil. Where a lot is too small, too steep or too rocky for a long leach field, a pit can do the same job by going down instead of out. You'll find a lot of them in Southern California, especially on older properties.

Valley Drilling Co has been a family-owned, C-42 licensed septic contractor since 1950, and drilling is in the name. We run our own drill rigs. Call (909) 795-6164, seven days a week from 8 AM to 8 PM, with after-hours emergency calls answered too.

What Is a Seepage Pit?

Think of it as a leach field turned on its end. Wastewater leaves the septic tank, where the solids settle out, and flows into the pit. The pit is a deep shaft, usually lined with perforated concrete rings or block and backfilled with gravel around the outside. The liquid seeps out through the sides and bottom into the surrounding soil.

Because it goes deep, a pit needs soil that drains well at depth and enough separation from groundwater. That's why counties ask for testing before they approve one.

What Are the Signs a Seepage Pit Is Full or Failing?

• Drains slow down across the house, even soon after the tank was pumped
• Gurgling in toilets and drains
• Sewage smell near the pit or the tank
• Wet soil or water around the pit cover
• Backups into the lowest shower or floor drain
• The tank fills up again much faster than it should

A "full" pit usually isn't full of sludge. Over the years, a slimy biological layer and fine solids seal the soil around the walls, and liquid can't get out as fast as it comes in. Skipping tank pumping speeds this up, because solids that should stay in the tank wash into the pit.

Can a Seepage Pit Be Repaired, or Does It Need Replacing?

Sometimes the pit isn't the problem. A clogged inlet, a broken line between the tank and the pit, or an overdue tank can cause the same symptoms, and fixing those may be enough. Pumping the pit itself can buy time on some systems, but it rarely brings back a pit whose walls have sealed.

When a pit has truly failed, the usual answer is a new pit drilled nearby and connected to the system, with the old one abandoned the way the county requires. Some properties add a second pit to share the load. We check the tank, the lines and the pit before recommending anything, and we'll tell you plainly whether it's a repair or a replacement.

How We Drill a New Pit

1. Testing. The county usually wants a percolation or soil test at pit depth first. See PERC and soil testing.
2. Layout and permit. The pit has to meet the county's setback distances, including from wells and property lines. We put the layout together and pull the permit. Plans are stamped by a licensed engineer when the county requires it.
3. Drilling. Our rig drills the shaft to the depth and diameter on the permit.
4. Building the pit. The liner goes in, gravel goes around it, and the line from the tank is connected.
5. Inspection and cover. The county inspects, then the pit gets its cover and the site is backfilled.

Seepage Pit or Leach Lines: Which Makes Sense?

Leach lines are shallow trenches that spread treated wastewater over a wide area. A seepage pit fits the same job into a small footprint by going deep. Neither one is right everywhere.

• Leach lines usually make sense when there's room, the soil near the surface drains well, and groundwater isn't close to the surface.
• A seepage pit usually makes sense when the lot is small or steep, the surface soil is tight but deeper layers drain, and the county allows pits in that area.
• Pits are off the table where groundwater is shallow or where the county doesn't permit them for new work.

The soil test and the county's rules make the final call. If your property has a drain field instead, our leach line repair page covers how those fail and get fixed.

Permits and Testing by County

Each county runs its own septic program, and the rules on seepage pits differ. Some areas allow them for new systems, some only for replacements, and some not at all. We work in San Bernardino, Riverside, Los Angeles, Orange and San Diego counties and pull the permits for the pits we drill.

Seepage Pit Questions

How long does a seepage pit last?

It depends on the soil, how much water the house uses and how often the tank is pumped. Many pits last for decades. Regular tank pumping is the biggest thing you control, because it keeps solids from washing into the pit and sealing the walls.

Does pumping the septic tank empty the seepage pit?

No. A tank pump-out removes sludge and scum from the tank, and the pit is a separate structure. Pumping the tank on schedule protects the pit, but if the pit itself has stopped draining, the tank will refill quickly and the backups will come back.

Can you drill a new seepage pit next to the old one?

Often, yes, as long as there's room to meet the county's setbacks and the soil at depth tests well. The new pit is connected to the system and the old one is abandoned the way the county requires.

Is a seepage pit allowed on my property?

That depends on your county, your soil and how deep the groundwater is. A soil or percolation test answers the soil question, and the county decides the rest. Call (909) 795-6164 and we'll walk you through what your county usually asks for.

More answers on our Septic FAQ, or read about our company.