Outside the city limits of Monticello almost every home we mow is on a septic system, and the drain field is usually right under the lawn. It works quietly for decades if it is treated right. Treated wrong, by heavy equipment, the wrong plants or a rerouted downspout, it fails, and that is one of the more expensive repairs a rural property can face.
Finding the drain field
If you do not know where it is, the county health department keeps permit records with a drawing of the system. Failing that, look for the clues. Drain field lines often show as parallel stripes of greener, faster-growing grass in a dry spell, or as slightly raised or slightly sunken parallel bands. The tank is usually within ten or fifteen feet of the house on the side the plumbing exits. Mark it once you know, because everybody who ever works on the property needs to know too.
Mowing over it
Mowing over a drain field is fine and is actually what should be there: a healthy stand of grass pulling moisture out of the ground helps the system. What matters is weight and moisture:
- Keep heavy equipment off. A riding mower is fine. A tractor, a loaded truck, a skid steer or a trailer full of firewood is not. The pipes are shallow and the gravel bed compacts.
- Never mow it when it is saturated. After a big rain the ground over a drain field is the last part of the yard to firm up. Ruts there are ruts in the system.
- Mow it at the normal height. Do not scalp; bare ground over a drain field erodes and exposes the lines.
- Leave the clippings. They are fine.
Bush hogging and the drain field
On larger properties the drain field is sometimes out in ground that gets a rotary cutter. Tell the operator exactly where it is. A tractor crossing the lines once on dry ground is usually survivable; running back and forth over them on wet ground crushes the pipe. If the field sits in an area that needs bush hogging, mow that section with a smaller machine instead. Our bush hog timing guide covers the ground-conditions side.
What to plant and what not to
Grass is the right cover. Shallow-rooted groundcovers and perennials are acceptable. Trees and large shrubs are not. Roots find the moisture and nutrients in the lines and fill them. The usual offenders in the Big Bend are willows, sweetgum, elm, maple and any large oak within thirty feet. Crape myrtles and hollies planted on the field for looks cause problems within a few years too. If a tree is already growing over the field, it is a question of when, not whether, and removal is cheaper than a new drain field. Our tree roots post explains how far roots actually travel.
Water: keep it off
A drain field works by letting treated water soak into the ground. Anything that adds more water to that ground makes it work harder or stop working:
- Route downspouts, gutters and sump discharge away from the field, not across it.
- Do not run irrigation zones over the drain field. The grass on top of it does not need it.
- Do not grade the yard so surface runoff collects there. If it is a low spot, fix the drainage around it; see our post on standing water and drainage.
Fertilizer and chemicals
Normal lawn fertilizer at normal rates is fine over a drain field. Do not dump it there because the grass looks lush; it already has plenty of nitrogen. Herbicides labeled for lawns are fine at labeled rates. Do not use the drain field as the place to rinse out a sprayer.
Signs the system is struggling
A drain field that is failing shows up in the lawn first. Grass that is unusually green and wet over the lines during dry weather, soggy ground that never firms up, a sewage smell after rain, or standing water at the end of the lines all mean the field is saturated. Slow drains inside the house usually follow. That is a call to a septic contractor, not a lawn problem, and the sooner the better.
FAQ
Can I build a bed or a patio over the drain field?
No. Anything that covers the ground stops it from breathing and adds weight. Keep it as open lawn.
Why is the grass over my drain field dying instead of greener?
Often the soil over the lines is shallow and dries out faster in a drought. Raise the cut and water lightly by hand in a dry spring; do not put a sprinkler zone there.
Is it safe to let kids and dogs play on it?
A properly working system is buried and safe. If there is ever surfacing effluent, keep everyone off until it is fixed.
Do you work around septic systems?
Every week. We mark them and mow them properly; see our services.
If you'd like your lawn handled by people who know where the drain field is and treat it accordingly, get in touch. We serve the rural properties around Capps, Lamont and the rest of Jefferson County.