Hydro-Logic Small Boy w/ KDF85 Catalytic Carbon Filter

The Hydro-Logic Small Boy w/ KDF85 Catalytic Carbon Filter is a compact, wall-mountable 2-stage inline water filter that ships with the KDF 85/catalytic carbon cartridge already installed. It removes up to 99% of chlorine and 90% of sediment, rust, silt, and particulates down to 5 microns at 1 GPM, delivering up to 60 gallons of treated water per hour with a total cartridge capacity of 6,000 gallons.

Hydro-Logic Small Boy KDF85 Specifications

All specifications are sourced directly from the product’s canonical data. Dimensions and weight are from the physical attributes recorded at the time of product ingestion.

Specification	Value
Brand	Hydro Logic
Model	Small Boy™ w/ KDF85 Catalytic Carbon
Filter Stages	2-stage, 10-inch filter housing
Filter Media	KDF 85 / Catalytic Carbon (pre-installed)
Flow Rate	1 GPM (60 gallons per hour)
Filter Capacity	6,000 gallons per cartridge
Chlorine Removal Rate	Up to 99%
Sediment Removal Rate	Up to 90% (rust, silt, particulates to 5 microns)
Volatile Organic Compounds	Removed (catalytic carbon stage)
Dimensions (L × W × H)	12 in × 14 in × 6 in
Weight	8.2 lb
Included Accessories	Wall-mountable metal bracket, garden hose connector, 4 ft feed line, 6 ft outlet line, 1/4 in shut-off valve, filter wrench, instructions

Why Choose the Hydro-Logic Small Boy w/ KDF85

The Small Boy™ is a well-established entry point in Hydro Logic’s filtration lineup. The version with the KDF 85/catalytic carbon cartridge pre-installed addresses a specific problem in many municipal water supplies: chloramines. Standard carbon blocks can handle free chlorine effectively, but chloramines — the disinfectant blends now used by most U.S. water utilities — require catalytic carbon to achieve meaningful reduction. This unit ships ready to use, with no additional cartridge purchase needed at setup.

The two-stage design works by passing water through the KDF 85 media first, which targets heavy metals, hydrogen sulfide, and bacteria, followed by the catalytic carbon stage, which reduces chlorine, chloramines, and volatile organic compounds. The result is water that is substantially cleaner before it enters your reservoir, irrigation lines, or any downstream filtration equipment such as a reverse osmosis membrane.

At a flow rate of 1 GPM (60 gallons per hour), the Small Boy handles the fill rates of most small-to-medium grow operations without creating a bottleneck. The 6,000-gallon cartridge capacity provides a meaningful service interval, and the 5-micron particulate threshold keeps sediment, rust, and silt from entering the system. The unit is compact enough to mount directly on a wall near the water source, and everything needed for installation ships in the box.

• KDF 85 + catalytic carbon pre-installed: No need to source and swap cartridges before first use. The upgraded filter media combination addresses both free chlorine and chloramines.
• Up to 99% chlorine removal: Protects beneficial microorganisms in living soil or organic systems, and removes a known stressor for hydroponic root zones.
• 5-micron sediment filtration: Catches particulate matter that could clog drip emitters, spray nozzles, or RO membranes further downstream.
• 60 GPH flow rate: Fills a 60-gallon reservoir in approximately one hour without adding pressure restrictions that stall fill cycles.
• 6,000-gallon cartridge life: Predictable replacement interval, easy to track on a per-fill basis.
• Wall-mountable with full hardware included: Metal bracket, hose connectors, feed and outlet lines, and a shut-off valve all included — installation does not require additional hardware.

Best Uses for the Hydro-Logic Small Boy w/ KDF85

This filter is sized and rated for applications where treated tap water is needed at reasonable volume without the footprint or cost of a full reverse osmosis system. It is not a de-mineralizing RO unit — it does not strip dissolved mineral content — but it reliably removes chlorine, chloramines, and particulate contaminants that interfere with plant health and downstream equipment.

• Pre-filter for an RO system: Running the Small Boy upstream of a compact reverse osmosis unit extends membrane life by removing chlorine, chloramines, and sediment before they reach the sensitive RO membrane.
• Stand-alone tap water treatment: For growers using a complete nutrient program with amended tap water, the Small Boy removes disinfectants and particulates without stripping the mineral content that buffers pH.
• Greenhouse and nursery fill stations: Wall-mount the unit near a hose bib to provide filtered water for hand watering, mixing tanks, or drip irrigation fills.
• Hydroponic reservoir fills: Directly treat incoming water before it contacts nutrient solution, protecting the microbial environment in organic DWC, ebb-and-flow, or NFT setups.
• Irrigation line protection: The 5-micron sediment stage catches particles that would otherwise clog drip emitters, sprayers, or valve seats over time.

Small Boy KDF85 vs Similar Inline Filters

The main distinction between the Small Boy™ with KDF85/catalytic carbon and a standard activated carbon inline filter comes down to the filter media. A conventional granular activated carbon (GAC) cartridge will reduce free chlorine effectively but performs poorly against chloramines. Catalytic carbon — produced by steam-activating carbon to a higher surface area and reactivity — catalyzes the decomposition of chloramines, making it the appropriate choice for growers on municipal water systems that use monochloramine or dichloramine as their primary disinfectant. If your water report lists chloramines rather than free chlorine, a standard carbon filter will leave most of the disinfectant load in place. The KDF 85 media adds a secondary stage targeting heavy metals, hydrogen sulfide, and microbial growth within the filter housing itself, which extends cartridge service life in degraded water conditions.

Compared to a full reverse osmosis system such as a Hydro Logic Micro 75 GPD RO unit, the Small Boy does not produce zero-ppm water. It treats water while leaving dissolved mineral content largely intact. This is the appropriate choice when source water TDS is already in an acceptable range and the primary concern is disinfectant removal, not mineral stripping. For growers who need to build nutrient solution from a clean baseline (very high TDS source water), the RO path remains necessary, and the Small Boy works well upstream as a pre-filter in that scenario.

Filters in this class from competing brands often require separate purchase of the upgraded media cartridge. The Hydro Logic version ships with the KDF85 cartridge installed, so the out-of-box experience does not require identifying and sourcing compatible replacement media before first use.

Compatibility

The Small Boy is designed for standard garden hose connections. The included garden hose connector adapts the inlet to a typical 3/4-inch hose thread, making it compatible with most residential and commercial hose bibs and spigots. The 4 ft feed line and 6 ft outlet line use standard fittings; the outlet line delivers treated water to a reservoir, bucket, RO system, or irrigation manifold.

As a pre-filter, the Small Boy is compatible with Hydro Logic’s own RO systems and with most third-party reverse osmosis units that accept standard inlet line diameters. The 1/4-inch shut-off valve included with the unit allows the water supply to be stopped at the filter without returning to the main supply valve.

The wall-mountable metal bracket fits standard drywall or stud mounting. The unit dimensions (12 in × 14 in × 6 in) should be accounted for in tight equipment closets or utility areas. The 8.2 lb weight is manageable for a single installer. For growers also monitoring their water chemistry, pairing this filter with an EC measurement tool lets you confirm that filtered water is within target conductivity range before adding nutrients.

This filter is intended for cold potable water lines. Do not use with hot water supply lines. Inlet water pressure should be within the range recommended by Hydro Logic for this unit; the included shut-off valve helps manage pressure during connection and cartridge changes.

Usage Guidelines

Under normal operating conditions at 1 GPM, the Small Boy will fill a 30-gallon reservoir in approximately 30 minutes and a 60-gallon reservoir in approximately one hour. The 6,000-gallon cartridge capacity provides a straightforward replacement schedule: a grower filling a 60-gallon reservoir three times per week will reach the cartridge replacement interval in approximately 33 weeks of continuous use.

Track usage by the volume of water processed rather than time elapsed. Chlorine and chloramine reduction efficiency declines as the filter media becomes saturated. Signs that the cartridge is approaching end-of-life include detectable chlorine odor in filtered water or a visible drop in flow rate. When either is observed, replace the cartridge regardless of whether the nominal 6,000-gallon threshold has been reached.

The KDF 85 media can support bacteriostatic activity within the filter housing during use, but the unit should not be left with stagnant water inside for extended periods (e.g., multi-week shutdowns) without being flushed before resuming use. Before the first use and after a cartridge change, flush 2–3 gallons of water through the filter to clear any carbon fines from the catalytic carbon stage. Flushed water will appear slightly cloudy initially; this is normal and clears quickly.

How to Install the Hydro-Logic Small Boy

All installation hardware is included in the box. The steps below apply to the standard wall-mount configuration using a hose bib supply.

1. Choose a mounting location near the water supply. The metal bracket mounts to a wall stud or solid backing. Position the unit so that the inlet is accessible to the feed line and the outlet line can reach your reservoir or RO system inlet without tension.
2. Mount the wall bracket using fasteners appropriate for your wall type. The unit should hang level; the housing is oriented vertically with the cartridge below the head.
3. Attach the feed line (4 ft, included) between the water supply (garden hose bib or shut-off) and the filter inlet. Hand-tighten the garden hose connector; use the included filter wrench for final tightening. Do not over-torque.
4. Connect the outlet line (6 ft, included) from the filter outlet to your reservoir, RO unit, or irrigation fill point.
5. Install the 1/4-inch shut-off valve on the feed line if not already in place. This valve allows you to stop water flow at the filter during cartridge changes without interrupting the main supply.
6. Verify the KDF85/catalytic carbon cartridge is seated in the filter housing. The cartridge ships installed; confirm the housing cap is hand-tight before turning on the water supply.
7. Open the supply slowly and check all connections for leaks. Tighten any dripping fittings by hand; use a wrench only if leaking persists.
8. Flush 2–3 gallons of water through the outlet line before use. Discard this flush water. The outlet water may appear slightly cloudy during the initial flush due to carbon fines; this clears within the first 2–3 gallons.
9. Begin normal use. Water is now treated and ready for reservoir fill or downstream RO system input.

Sources & Further Reading