Leach Field Repair & Replacement in Rural Sonoma County & West Marin

How a leach field works

After solids settle in the septic tank, the liquid effluent flows to a distribution box that splits it among perforated pipes laid in gravel-filled trenches. The effluent soaks into the soil, where it is filtered and treated. Over years of use, a layer of biological growth forms where the gravel meets the soil. That layer helps with treatment, but if it thickens too much, or if the soil around the trenches stays saturated, the field can no longer absorb what the house sends it.

Signs a leach field is struggling

• Slow drains or gurgling throughout the house, especially in the lowest fixtures
• Wastewater backing up into a tub, shower, or floor drain
• Soggy, spongy ground or standing water over the leach lines
• Grass that is noticeably greener and lusher over the field than elsewhere
• Sewage odors in the yard
• Liquid in the tank above the outlet, or flowing back from the field when the tank is pumped

Common causes, and what fixes them

• Overdue pumping. When a tank fills with sludge and scum, solids carry over into the field and clog it. Pumping alone won't unclog a damaged field, but it stops the damage from getting worse. See tanks, baffles, and risers.
• A broken or tilted distribution box. If the box settles or cracks, it can send all the effluent down one line and overload it. Releveling or replacing the box is often a modest repair.
• Roots and crushed lines. Tree roots invade pipes and trenches, and vehicles crush lines that run under driveways or parking areas. Damaged sections can be jetted, cleared, or replaced.
• Too much water. Leaking fixtures, a running toilet, a water softener discharge, or roof and surface runoff draining onto the field can overload it. Redirecting runoff and fixing leaks can make a real difference.
• Saturated winter soils and high groundwater. Many rural properties here have shallow soils, clay, or seasonal groundwater close to the surface. A field that copes in summer may fail after weeks of rain.
• A field at the end of its life. When the soil around the trenches is clogged after decades of use, the answer is a new field, usually in the reserve area set aside for it.

How contractors diagnose the problem

A good diagnosis starts with the county permit records, then opening and pumping the tank, inspecting the baffles and outlet, exposing the distribution box, and probing the field for saturation. A camera inspection of the lines shows roots, breaks, and crushed pipe. A load test, running a measured amount of water through the system, shows how much the field can actually take.

Repair or replacement: how the counties draw the line

Sonoma County. Under Permit Sonoma's onsite wastewater rules, replacing up to 25 percent of the existing dispersal system, measured cumulatively by total linear footage, is handled as a repair. Replacing more than that is a replacement, which brings the system up to current design standards and typically involves a site evaluation and an engineered design. Because the 25 percent is cumulative, past repairs count toward it.

Marin County. Repairs and replacements are permitted through Environmental Health Services. Marin is currently updating the program that sets its inspection and repair standards, so requirements may change. A system replaced after a failure generally has to meet the code in effect at the time.

Protecting a leach field

• Pump the tank on schedule, generally every three to five years depending on tank size and household
• Keep vehicles, livestock, and heavy equipment off the field
• Direct roof downspouts and surface runoff away from the field
• Don't plant trees or thirsty shrubs over or next to the lines
• Spread out laundry and fix leaking fixtures
• Keep grease, wipes, and chemicals out of the drains

Soggy ground over the field or drains backing up? Call (707) 867-1221 or request an inspection or estimate and we'll connect you with a local septic contractor.