Mound Septic System
A mound septic system is a large, above-ground wastewater treatment option that relies on imported sand to safely filter and disperse effluent. This design is often used when native soil conditions are not suitable for traditional drainfields, providing a reliable and effective solution for challenging sites.
Mound Septic at McNair Septic
A mound is a large, above-ground septic system that uses imported sand for filtration. It consists of a septic tank, a pump tank and the drainfield which is in a mound of sand. The pump chamber can be incorporated into the septic tank, but is more commonly found in its own second tank. The septic tank must be placed accordingly so that it is downhill from the home/building’s plumbing. A bio-microbial process in the septic tank treats the waste before it reaches the pump chamber. Further settling occurs in the pump chamber, ensuring that the pump does not send solid material to the pods.
The pump chamber contains two floats: a low level/off float (lower) and a high-water alarm float (higher). Time dosing is set upon installation. The system will turn the pump on a set number of times each day for a set amount of time. If the system pumps too much effluent out of the pump chamber, the low level/off float will turn the pump off automatically until its next dose time. If the effluent level in the pump chamber rises too high between doses, the high-water alarm float will trigger an alarm which indicates that something is wrong with the system or that dose times need to be adjusted to occur more frequently. Time dosing protects the mound from flooding, which reduces the effectiveness of the filtration processes.
The pump transports effluent to the mound. There, a valve box evenly distributes the effluent between the lateral lines. The system must use a pump even if gravity flow can be achieved from the pump chamber to the mound. This is to ensure that the valve box is pressurized so all of the laterals receive the same amount of effluent. Each lateral line has orifices that allow the effluent to reach the soil throughout the entire mound at the same rate. The effluent then filters through the sand in the mound to the soil and is clean by the time it reaches the water table.
A mound system should have an operation and maintenance inspection done twice every year. Concurring reports may need to be turned in to the county. Further, inspections may be required at various points during the installation of the system.
A common mound size is 34 feet by 93 feet, but shapes vary significantly with design because of the large size of the mound. Septic systems are sized according to the amount of waste they will be treating, usually estimated by the number of bedrooms in the home. For nonresidential buildings, water usage usually determines the size.
Upon installation, grass can be grown on the mound. A valve box lid and 24-inch riser lids above the tanks will all be visible after installation. Each of these lids will be flush with the final grade and can be walked on, mowed over or disguised to lessen noticeability. Four-inch monitoring ports will be visible on top of the mound.
Mounds should be treated as fragile to increase their longevity. Animals should not be allowed on mounds and vehicles should not be driven over them. Vegetation with intrusive roots should not be planted near them. Finally, a home owner should be mindful of what is going into the system.
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FAQs About Mound Septic Systems
Why would I need a mound septic system instead of a traditional system?
A mound system is typically required when the soil is too shallow, the water table is high, or site conditions prevent a standard drainfield from functioning properly.
How does a mound septic system work?
The system uses a septic tank and pump chamber to deliver effluent into a raised sand mound, where it filters through the sand before dispersing into the natural soil, ensuring clean water reaches the water table.
What maintenance does a mound system require?
Mound systems require operation and maintenance inspections twice per year, and reports may need to be filed with the county to ensure compliance.
How big is a typical mound system?
A common mound size is about 34 feet by 93 feet, though the exact design depends on the number of bedrooms in a home or water usage for non-residential buildings.
What precautions should I take with a mound septic system?
Mounds should be treated as fragile: avoid driving or placing heavy animals on them, don’t plant trees with invasive roots nearby, and be mindful of what goes into your septic system.
The Process
Planning
All we need is your parcel number or address to begin. We research your property in advance, gather details about your future plans, and may schedule a site visit or call. Any questions are addressed quickly to keep the process moving.
Soils Evaluation
Most projects start with a soil evaluation (perc test), the first step toward system approval. We handle everything—from digging and testing to county applications, fees, and paperwork—while keeping you updated every step of the way.
On-Site Septic System Design
After completing the soil evaluation, we quickly create a detailed, cost-effective septic design, typically within one to two weeks, that includes all calculations, maps, and specifications, while handling every detail of the submittal process for you.
Review and Permitting
Most counties allow up to three weeks to review septic designs and soil evaluations, though some return them sooner. Once approved, we’ll send you a copy and can also forward it to licensed installers so you can receive system bids.
Taking Care of You
We handle everything—even the required county as-built map—so your septic system is approved and recorded. With no complex contracts, we start right away and keep things moving. Consultations are always free, so call us anytime.
Support
We can assist you in finding reputable septic installation and maintenance companies that can service and maintain your new system.
