What is a leach field?
A leach field is the part of a septic system where wastewater from the tank soaks into the soil and gets treated. It's also called a drain field, disposal field or soil absorption system. Most of the treatment happens here, so solids need to stay in the tank and out of the field.
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How does a leach field work?
- Wastewater leaves the house and flows into the septic tank.
- In the tank, solids settle to the bottom as sludge and grease floats to the top as scum.
- The clearer liquid in the middle, called effluent, flows out to the leach field.
- In the field, the effluent runs through perforated pipes in gravel trenches or chambers and seeps into the soil.
- Soil and the microbes living in it filter and treat the effluent before it reaches groundwater.
Leach field designs in Arizona
Under ADEQ's general permit for conventional systems (4.02), the effluent is treated in trenches, beds or chambers, or disposed of through a seepage pit. Where the soil or site won't support a conventional field, ADEQ has general permits for other designs, including pressure distribution, mound systems, sand-lined trenches and subsurface drip. See alternative septic systems in Arizona.
Signs a leach field is failing
- Soggy ground or standing water over the field
- Grass that's noticeably greener over the trenches than elsewhere
- Sewage odor in the yard
- Drains that slow down again soon after the tank is pumped
During a home-sale inspection, inspectors look for ponding and spongy or damp soil over the distribution lines, and may run a camera through the lines, according to the University of Arizona's guide to the inspection program.
How to protect it
- Pump the tank on schedule so solids never reach the field
- Spread out laundry and other heavy water use
- Keep cars, trailers, livestock and heavy equipment off it
- Keep trees and deep-rooted plants away from the trenches
- Send roof drains and runoff somewhere else
For repairs, see leach field repair or call (480) 542-8315.
Questions people ask
Is a leach field the same as a drain field?
Yes. Leach field, drain field, disposal field and soil absorption system all mean the same part of the system.
Where is my leach field?
It's usually downhill from the septic tank. If the county has permit drawings on file, they may show it. A contractor can also trace the line from the tank.
Can I build a patio or shed over the leach field?
No. The soil needs air and has to stay uncompacted to treat the effluent, and the field has to stay reachable for repairs.
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Tell us what's going on and a local septic contractor will call you back. Or call (480) 542-8315 now.
Call for pumping, repairs or a home-sale inspection.
Call (480) 542-8315