OPERATING TIER
Above-ground oil-water separators in the 5–10 GPM range are typically deployed where wastewater treatment supports operations rather than defining them. These systems serve maintenance bays, washdown areas, fueling points, and utility facilities where space is limited, staffing is lean, and equipment is expected to perform reliably without constant attention.
At this scale, separators rarely fail because gravity separation is flawed. They fail because internals foul quietly, inspection is deferred, and systems are selected by nominal flow rate alone—without considering solids behavior, temperature swings, or how the separator will actually be accessed and maintained.
Mercer’s 5–10 GPM above-ground separators are designed for real wastewater conditions, including free oil, suspended solids, intermittent loading, and variable operating cycles. The design prioritizes inspectability, cleanability, and long-term reliability rather than idealized influent assumptions.
Mercer has deployed systems at this scale in demanding industrial, utility, and energy environments where access, inspectability, and long-term serviceability determine whether a separator remains an asset or becomes a maintenance problem.
Built To Scale
This product family follows a compact, low-flow footprint philosophy, with internal volume and coalescer sizing adjusted by flow range and application requirements.
Please Note: Exact materials, dimensions, and configurations vary by application. Carbon steel construction is typically introduced at higher flow ranges where structural requirements dictate.
FIELD-PROVEN SYSTEMS
Small flows can still pose big problems.
The installations shown represent actual Mercer systems operating in the 5–10 GPM range, deployed in facilities where access, uptime, and maintenance realities drive long-term performance.
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
TRUSTED BY INDUSTRY LEADERS
A small sampling of companies with Mercer separators operating within the 5–10 GPM family range.
ENGINEERED TO SOLVE
Even modest solids loading can foul corrugated plastic or tube-style coalescers. Once solids lodge in internal pockets, oil removal efficiency drops and cleaning becomes impractical.
Small separators are often ignored because they are difficult to inspect or access. Over time, this leads to emergency cleanouts, unexpected failures, or premature replacement.
Systems selected strictly by flow rate—without considering oil type, solids behavior, temperature, or access—often appear adequate initially and fail months later in real service.
CORE TECHNOLOGY
A tank provides residence time.
Separation performance is determined by what happens inside the coalescer.
Mercer’s Multi-Pack™ coalescer is not generic media. It is a purpose-engineered separation system built around five core design elements that control oil rise, solids shedding, hydraulic stability, and real-world maintainability—especially in applications where small systems are easy to ignore until they fail.
The Multi-Pack™ uses flat, steep-angled plates rather than corrugated or honeycomb media. Flat plates support predictable droplet capture while allowing solids to shed cleanly instead of lodging in pockets that quietly choke performance over time.
Learn MorePlate spacing can be adjusted beyond or below standard spacing to tune separation performance to actual conditions—oil type, temperature and viscosity effects, solids behavior, and desired maintenance intervals.
Learn MorePlates are arranged in a herringbone configuration that organizes internal flow paths and segregates areas where oils rise from areas where solids settle. This stabilizes hydraulics when flows cycle on and off, which is common in low-GPM applications.
Learn MoreAs oil coalesces and solids shed from the plates, they enter dedicated Chimney Zones™ designed for separation—not turbulence. These quiescent chambers allow oils to rise and solids to settle without re-entrainment, even during solids spikes.
Learn MoreThe Multi-Pack™ is fully removable as a single assembly. Operators can remove the pack, visually inspect it, clean it, and return it to service without dismantling internals or replacing disposable media.
There has never been a Multi-Pack™ removed from a tank where operators could not see through to the opposite side before cleaning begins. Surface films may be present. Clogged pockets are not.
Learn MoreAt this flow range, separators often appear to work—until they don’t.
Performance failures at 5-10 GPM are rarely dramatic. They show up as gradual fouling, declining oil removal, increased maintenance attention, and growing uncertainty about whether the system is still doing its job. In many cases, the separator is left in service long after internals have effectively stopped performing.
The Multi-Pack™ is engineered to prevent that outcome. By shedding solids predictably, maintaining stable internal hydraulics, and allowing full visual inspection and cleaning, the coalescer ensures that separation performance can be verified, restored, and relied upon over time—rather than assumed.
PROVEN LONGEVITY
Built to Stay in Service
Many of the systems shown below were installed years ago and remain in continuous operation today. These are not retired examples or decommissioned assets. They are active separators, still managing oil and solids under real operating conditions.
Longevity at this scale is not accidental. It is the result of internal designs that can be inspected, cleaned, and adjusted over time rather than replaced.
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
Above Ground
5 & 10 GPM
INDUSTRY APPLICATIONS
Maintenance bays and wash areas generate oil-bearing wastewater with intermittent solids spikes. Mercer systems are selected to remain serviceable between cleanings.
Learn more
Compressor rooms, generator facilities, and small process discharges require predictable separation without constant oversight.
Learn More
This family has also been applied in light manufacturing, municipal support facilities, and specialty service operations where access and reliability matter more than nominal flow.
Learn More
For small flow applications, the biggest risk is not overloading — it’s underestimating how fast conditions change. Mercer reviews your actual drainage area, wash activities, and solids sources to confirm the 5 or 10 GPM model is the right fit.
Talk to Mercer to confirm sizing before installation and avoid premature maintenance or compliance issues.
Cleaning frequency depends on how much solids and oil the system sees, not calendar time. The removable Multi-Pack™ allows operators to quickly pull, inspect, and clean the plates so maintenance is based on actual conditions instead of guesswork.
Yes. These models are commonly used for intermittent flows such as vehicle wash areas, maintenance bays, and small stormwater collection points, provided solids loading and peak flow conditions are understood.
Performance at low flow rates is easily disrupted by turbulence, short-circuiting, and poor access for cleaning. Mercer’s inlet control, coalescing internals, and serviceable design ensure the separator continues to perform after installation — not just on day one.
Tell us about your project and we’ll provide the right configuration drawings for your site and flow conditions.
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