Living with a septic mound in Delaware, Union, or Madison County

If your house outside Marysville, Ostrander, or London has a long grassy hump in the yard with a few short white pipes poking out of it, you own a mound. Here is how it works and how to keep it working for decades.

What is inside the hump

A mound is a treatment bed built upward because the natural soil is too shallow or too wet to treat effluent on its own. Ohio State University Extension describes the construction plainly: selected sand goes on top of the natural soil, a layer of gravel or chambers surrounds small distribution pipes on top of the sand, and soil fill covers the whole bed to protect those pipes from freezing. Effluent does not flow in by gravity. It leaves the septic tank, collects in a dosing tank, and a pump sends a measured volume up into the mound's pipes at intervals.

That design fits much of this region. Extension estimates that about 53 percent of Ohio soils have a limiting layer too shallow to offer 36 inches of suitable soil, and mounds are used where that layer sits 12 to 36 inches down. On the till plain north and west of Columbus, the limiting layer is usually seasonal perched water.

The parts to know by name

• Septic tank: settles solids and holds scum, just as in any system. Newer ones have two compartments and an outlet filter.
• Dosing tank (pump chamber): stores effluent between doses and houses the pump.
• Floats: switch the pump on and off, plus a higher float that trips the alarm.
• Control panel and alarm: usually on the house or on a post near the dosing tank, with a light, a buzzer, and a test or silence button.
• Inspection ports: the short pipes on the mound, which let a technician check for ponding inside the bed.

If you cannot find all five on your property, ask the health district for the permit drawing before the next service visit.

Habits that keep a mound alive

Extension's list is short and specific. Pump the septic and dosing tanks every one to five years, depending on use. Do not plant trees or shrubs on the mound, because roots clog the distribution pipes. Never compact the soil downslope of the mound with paving, buildings, or parked cars; that downslope ground is where treated effluent spreads out and soaks away.

Add a few Central Ohio habits to that list:

• Keep grass or low perennials on the mound. Bare sand erodes, and a mound grown over with brush has root problems on the way.
• Keep the panel breaker on and test the alarm a few times a year.
• Spread laundry across the week. A dosing tank sends only a set volume at a time, and a Saturday of back-to-back loads can reach the high-water float.
• Route sump pumps and downspouts away from the mound and from the downslope area.
• Do not let plows pile snow on the mound, and keep snowmobiles and ATVs off it.

What the county expects

Every Ohio health district has run an operation and maintenance program since the 2015 rules, and mounds are handled differently from county to county. Delaware Public Health District's permit-length chart puts mounds, drip systems, and pumped elevated systems on one-year operation permits, compared with five years for a gravity septic-to-leach-field system. Licking County Health Department inspects soil absorption systems, mounds included, every five years. Union County enrolls every system on a five-year permit. In each case, a service report signed by a registered service provider, or a pumping receipt, can usually stand in for a county inspection, so keep them together.

A one-year permit is not a penalty; it reflects the fact that a pump, floats, and a panel can quietly fail between visits.

What a mound service visit covers

A proper service visit on a mound goes beyond pumping. The septic tank and the dosing tank are opened and measured, and the dosing tank is pumped if solids have settled on its floor. The pump is run through a full cycle while someone watches the discharge, the floats are lifted by hand to confirm the on, off, and alarm points, and the alarm is tested at the panel. On timed-dose systems, the timer settings are checked against the design. Out on the mound, each inspection port is uncapped to look for ponded effluent inside the bed, and the toe and the downslope area are walked for wet spots. Some designs include a cleanout at the end of each distribution lateral so the small pipes can be flushed if slime has built up inside them. Everything goes on a written report, the document your county operation permit will ask for.

If a visit skips the dosing tank, it skipped half the system.

Warning signs and what they usually mean

• Alarm on, pump silent: a tripped breaker, a failed pump, or a stuck float. Cut water use and call.
• Alarm after a heavy water day that clears overnight: the pump is keeping up slowly, or the dosing settings need adjusting. Book a service visit.
• Wet or seeping ground at the toe of the mound: effluent breaking out of the side, often from compacted downslope soil, uneven dosing, or a clogged bed.
• Standing liquid in the inspection ports: the sand, or the natural soil beneath it, is not accepting effluent as fast as it arrives.
• Sewage odor near the mound: check that the ports are capped and the dosing tank lid is sealed, then call.

When a mound needs more than service

Pumps wear out and floats fail; those are repairs. A bed that ponds persistently, or a toe that stays wet into a dry summer, may need rehabilitation or replacement, which is permitted work designed from a current soil evaluation. Catching dosing problems early is what keeps a mound from ever reaching that point.

If the alarm is sounding right now, the alarm FAQ covers the first steps, and a same-day service visit is one phone call away.