The Complete Hydrologic RO Buyer's Guide for Cannabis Growers (2026): Stealth-RO, Evolution-RO, and the Sizing Decision That Makes the Brand Work

Hydrologic is the canonical cannabis-grade RO brand. Retailer's complete 2026 guide to the lineup, sizing math, chloramines question, and Stealth-RO vs Evolution.

A customer walked into the shop last week asking which RO filter to buy. He'd been growing on 320-ppm city tap water for three cycles, fighting calcium deposits in his coco pots and watching his Athena feed schedule drift away from the published targets because his input water EC was throwing off the math. He'd narrowed his RO choice to Hydrologic Stealth-RO 150 or one of the cheap Amazon options. The honest answer: the cheap Amazon RO will produce clean water for one cycle, then the flow rate will collapse, the pre-filters will clog, the membrane will foul, and replacement parts won't be available at any local shop. The Hydrologic Stealth-RO 150 at $300 will produce clean water for five years with annual pre-filter replacement and biennial membrane replacement. The cost-per-gallon over five years works out to roughly the same as the cheap RO when you include replacement parts; the difference is reliability and serviceability.

Every premium cannabis nutrient brand we cover in this cluster (Athena, Heavy 16, HGV, Drip Hydro, House & Garden, CANNA) assumes input water EC at or below 0.4 mS/cm for the published feed schedule to work as designed. Most US tap water tests at 0.5 to 1.2 mS/cm. The math doesn't work without RO filtration. Hydrologic is the canonical cannabis-grade RO brand with a complete lineup spanning hobby through industrial scale, the best waste-water efficiency in the hydroponic category, and the accessory ecosystem that lets you scale your filtration as your grow scales. We sell the full Hydrologic line at Modern Farms, plus the replacement filters and membranes that keep the system working over its 5-year lifespan.

The 30-Second Answer (For People Who Just Want to Buy)

Hydrologic is the cannabis grow community standard. The lineup splits into five tiers. For most home grows, the Stealth-RO 150 at approximately $300 is the right answer. For multi-tent hobby or pro-sumer setups, the Stealth-RO 300 at approximately $450. For light commercial operations (10+ lights, 5-10 reservoirs), the Evolution-RO 1000 at approximately $700. For serious commercial (multi-room, hundreds of lights), the HyperLogic commercial line is custom-built. For growers who only need chlorine and chloramine removal without RO (rare; works only on very-soft input water), the Tall Boy or Big Boy dechlorinators at $200-400.

The single most important upgrade for most growers: if your municipal water is chloraminated (most US cities are), the standard carbon pre-filter doesn't remove chloramines. You need the KDF/catalytic carbon filter upgrade or the ChloraShield filter, which adds approximately $40-60 to the system cost. Skipping this upgrade means chloramines pass through to your reservoir, damage beneficial microbes, and shorten the RO membrane life.

The waste-water efficiency claim is real. Hydrologic Stealth-RO ships with both 1:1 and 2:1 flow restrictors in the box. Most competitor RO systems are fixed at 3:1 or 4:1 (3 or 4 gallons of waste per 1 gallon of product). At 1:1, Hydrologic produces 50 percent less wastewater than typical RO systems, which matters for water-conscious growers and operations on metered water.

Buy Hydrologic if you grow cannabis in coco, rockwool, soilless, or DWC with premium nutrients; if you're on city water above 0.4 EC or chloraminated municipal water; if you have well water with iron, sulfide, or hardness above 200 ppm; or if your nutrient feed schedule depends on clean input water (Athena, Heavy 16, HGV, Drip Hydro, House & Garden, CANNA all do). Skip Hydrologic for cannabis grows where your tap water already tests below 200 ppm and isn't chloraminated (rare but exists) and where your nutrient brand doesn't depend on a published feed schedule.

The Hydrologic Lineup, Mapped Clearly

Five product tiers covering every grow scale from a 4x4 hobby tent to industrial cannabis facilities. The full map.

Pre-RO filtration (no membrane, dechlorination and sediment only)

These products remove chlorine, chloramines (with upgrade), sediment, and some heavy metals, but do NOT reduce TDS or PPM. Right for growers whose tap water already tests below 200 ppm and only needs cleanup, not desalination. Rare use case for cannabis but exists.

• Hydrologic Small Boy ($150): the compact countertop dechlorinator. 1 GPM flow rate, removes up to 99 percent of chlorine and sediment. Right for very small grows or as a pre-treatment in front of an RO system.
• Hydrologic Tall Boy ($230): the mid-size dechlorinator. 2 GPM flow rate, removes 99 percent chlorine. Tall Boy can be upgraded to a Stealth-RO 100 unit with a conversion kit (HL 33021) if you decide you need RO later.
• Hydrologic Big Boy ($420): the high-flow dechlorinator. 7 GPM flow rate, removes 99 percent chlorine and 95 percent sediment, includes inlet and outlet pressure gauges to monitor clog status. Right for whole-house cannabis grow setups where pre-filtering at the main water line makes sense.

Stealth-RO line (the canonical hobby and pro-sumer RO systems)

The product family Hydrologic built its reputation on. Both Stealth-RO models include 1:1 and 2:1 flow restrictors in the box, the Membrane Power Flush Kit, sediment pre-filter, carbon pre-filter, garden hose connector, inline shut-off valve, and all necessary tubing.

• Hydrologic Stealth-RO 150 ($300): 150 GPD, 98 percent contaminant removal, the right pick for most home hobby grows from single 4x4 tents through 4x8 setups. Dimensions roughly 18.5 x 16 x 6 inches, wall-mountable. The most popular Hydrologic product and the canonical recommendation across the cannabis grow community.
• Hydrologic Stealth-RO 300 ($450): 300 GPD, dual membrane, same 98 percent removal. The right pick for multi-tent hobby setups or growers who want to fill reservoirs faster. Same form factor as the 150 with a second membrane housing.

Evolution-RO line (light commercial, tankless, high flow)

• Hydrologic Evolution-RO 1000 ($700): 1000 GPD tankless RO system. 42 gallons per hour of pure water. 95 percent contaminant removal. Designed for light commercial cannabis operations, greenhouses, multi-room hobby setups, or commercial garden operations. Can produce up to 1500 GPD with the optional Pressure Booster Pump accessory. Includes custom KDF/catalytic carbon filter for chloramines removal as standard.

HyperLogic Commercial and Industrial lines

Custom-built systems for commercial and industrial cannabis operations. Each system is configured based on site water chemistry and production targets.

• HyperLogic Commercial: 2,000 to 19,000 GPD configurations. Custom-built per facility specifications. Lowest wastewater-to-product ratios in the hydroponic industry (up to 80 percent recovery rate).
• HyperLogic Industrial: 28,800 GPD and greater. For large commercial cannabis facilities and industrial agricultural operations.
• Hydroid Compact RO: smaller commercial form factor for operations that need commercial flow rates without the full HyperLogic footprint.
• Breakwater RO: alternative commercial offering for specific water chemistry profiles.

The accessory ecosystem

Hydrologic systems are modular. The accessories that matter for cannabis growers:

• Pressure Booster Pump ($180): required for water sources below 50 PSI (common with well water, some apartment setups). Increases pressure to optimal range for membrane efficiency.
• Float Valve ($25): auto-shutoff for unattended reservoir filling. Mount in your reservoir or tank, set desired water level, walk away.
• Pressure Regulator ($45): for water sources above 80 PSI (some municipal supplies). Protects the membrane from pressure damage.
• Flowmaster Flow Meter ($30): tracks total gallons produced, useful for replacement scheduling.
• Pre-Evolution High Capacity Pre-Filter ($120): for Evolution-RO 1000 users on hard water or high-sediment sources, extends membrane life dramatically.
• ChloraShield Filter Upgrade ($45): for chloraminated municipal water. Mandatory on city water in most US metropolitan areas.
• KDF/Catalytic Carbon Filter Upgrade ($40-60): alternative to ChloraShield for chloramines, plus removes iron, sulfur, heavy metals. Best choice for well water.
• Replacement Sediment Filter ($15): change every 2-4 months.
• Replacement Carbon Pre-Filter ($25): change every 2-4 months.
• Replacement RO Membrane ($90 for Stealth-RO; $180 for Evolution-RO): typical lifespan 2-3 years with proper pre-filter maintenance.

The Sizing Decision Framework

The most-asked Hydrologic question: which size do I need? The answer depends on your daily water consumption, your grow scale, and your tolerance for filtration runtime.

The rule of thumb

Hydrologic's own published sizing rule: estimate your daily water consumption, add 20 percent for safety margin, then double the total so you're not running the filter more than 12 hours per day. The math: 30-gallon daily need + 20% = 36 gallons. Doubled = 72 GPD minimum sizing. Round up to the next available size (in this case, the Stealth-RO 75 if it still existed, or step up to the Stealth-RO 150).

Daily water consumption by grow scale

Estimates for a typical cannabis grow at peak demand (mid-to-late flower, the highest water use stage):

• Single 2x4 tent (4 plants in 3-gallon pots): 5-10 gallons per day at peak. Need: minimum Stealth-RO 75 or 100; Stealth-RO 150 is right pick for headroom.
• Single 4x4 tent (4 plants in 5-gallon pots): 15-25 gallons per day at peak. Need: Stealth-RO 150 is the canonical choice.
• Single 5x5 tent or 2x 4x4 tents: 30-50 gallons per day at peak. Need: Stealth-RO 150 with overnight runtime, or step up to Stealth-RO 300 for faster fills.
• 3x 4x4 tents or 1x large commercial flower room (10 lights): 75-150 gallons per day at peak. Need: Stealth-RO 300 or Evolution-RO 1000.
• Multi-room commercial (24+ lights): 300-1000 gallons per day at peak. Need: Evolution-RO 1000 with booster pump, or HyperLogic Commercial system.
• Large commercial (50+ lights, multi-room): 1000+ gallons per day. Need: HyperLogic Commercial or Industrial.

The runtime trade-off

You can save money by undersizing and running the filter longer, but at a real cost. A 30-gallon daily need on a Stealth-RO 100 means roughly 7 hours of filter runtime. The same need on a Stealth-RO 150 takes 4-5 hours. On a 300, less than 2 hours. The Stealth-RO 100 is cheaper, but you're committed to filling your reservoir over half the workday, which constrains when you can do other operations.

The right sizing for most home growers: pick one size up from the minimum that math gives you. The headroom matters when your grow expands, when your source water gets harder over time (well water especially), and when you want to fill a reservoir on demand rather than scheduling around filter runtime.

The headroom rule

Hydrologic systems live their best life at 30-70 percent of rated capacity. A Stealth-RO 150 running 4 hours a day to produce 25 gallons is in its sweet spot. The same filter running 18 hours a day to produce 110 gallons is being pushed; pre-filters clog faster, the membrane fouls earlier, and the lifespan drops. Buying one size larger than the strict math says is the move that extends the equipment lifespan.

The Chloramines Question (The Section Most Growers Skip)

The single most important Hydrologic upgrade for most growers. Skipping this destroys the brand's value proposition. Worth understanding clearly.

Chlorine vs chloramines

Municipal water suppliers disinfect tap water with one of two chemicals: chlorine or chloramines. Chlorine is the older standard; it dissipates from water with time and aeration. Chloramines are the newer standard (most US cities switched in the 2010s); they're more stable, don't dissipate readily, and require active filtration to remove.

Hydrologic's standard carbon pre-filter handles chlorine effectively. The standard carbon pre-filter does NOT remove chloramines adequately. If your municipal water is chloraminated (most US cities are; check your local water quality report or call your water utility), the standard system passes chloramines through to your reservoir.

Why chloramines matter for cannabis

Chloramines damage beneficial microbes in the root zone (mycorrhizae, beneficial bacteria), shorten the RO membrane life by oxidizing the thin-film material, and contribute to flavor and aroma issues in finished flower. For coco and soil growers running microbial-inoculant programs (compost teas, mycorrhizal inoculants, Heavy 16's Prime), chloramines are particularly damaging because they undo the inoculant work.

The two upgrade paths

KDF/Catalytic Carbon Filter Upgrade ($40-60): the most common upgrade. Replaces the standard carbon pre-filter with a catalytic carbon that handles chloramines plus iron, sulfur, and heavy metals. Best choice for well water or city water with multiple contaminants. Lifespan: 2,000 filtered gallons.

ChloraShield Filter ($45): Hydrologic's chloramine-specific filter that drops into the same housing as the standard carbon pre-filter. Slightly more chloramine-specific than KDF/catalytic carbon. Lifespan: 7,000 filtered gallons. Best choice for city water where chloramines are the primary concern.

The choice between KDF and ChloraShield depends on your water source. City water with chloramines and minimal other contaminants: ChloraShield. Well water or city water with chloramines plus iron, sulfur, or heavy metals: KDF/catalytic carbon. For commercial Evolution-RO 1000 systems, the KDF/catalytic carbon is included standard.

How to know if your water has chloramines

Three options. First, check your local water utility's annual water quality report (mailed annually to all customers; often posted online). The report identifies disinfectant type. Second, call the utility and ask. Third, test for chloramines specifically (test strips and lab analysis available). Most US cities above 50,000 population use chloramines; most rural water systems and well water do not.

If you can't determine your water source's disinfectant type, default to assuming chloramines are present and run the ChloraShield or KDF upgrade. The cost is small ($40-60 one-time, plus replacement every 7,000 gallons), and the protection against beneficial microbe damage and premature membrane failure is significant.

Well Water Challenges

Growers on well water face specific challenges that city-water growers don't. Hydrologic addresses these but requires specific configurations.

The well water reality

Well water typically presents:

• Higher TDS/PPM (often 400-800 ppm): mineral hardness from limestone, dolomite, or other rock formations. Shortens RO membrane life if pre-filtration doesn't capture it first.
• Iron and manganese: common in well water, causes orange/brown staining. Iron specifically fouls RO membranes if not pre-filtered.
• Hydrogen sulfide (rotten egg smell): common in wells in certain geological areas. Damages membranes and creates terrible flavor in any downstream uses.
• Iron bacteria: microbial growth that's difficult to remove and clogs filters quickly.
• Lower water pressure: well pumps often deliver 30-50 PSI vs city water at 50-80 PSI. The membrane's efficiency depends on pressure.
• Colder water temperature: well water is typically 50-60°F vs city water at 60-70°F. Cold water flows slower through the RO membrane, reducing throughput.
• Higher sediment: wells with shallow drilling or weathered casings produce sand and grit that clogs carbon filters quickly.

The well water configuration

For most well water cannabis grows, the configuration is:

• Hydrologic Stealth-RO 150 or larger (depending on consumption) as the base system
• KDF/Catalytic Carbon Filter Upgrade (handles iron, sulfur, chloramines if present, heavy metals)
• Pre-Evolution High Capacity Pre-Filter (for Evolution-RO 1000 users) or larger external sediment pre-filter (for Stealth-RO users). The filter extends membrane life by capturing well-water sediment before it reaches the RO membrane
• Pressure Booster Pump if your well pressure is below 50 PSI
• More frequent pre-filter replacement (every 1-2 months vs the standard 2-4 months for city water)

The iron bacteria problem

If your well has iron bacteria (orange slimy buildup in plumbing, brown/orange staining), standard RO pre-filtration won't fully address it. You may need a separate iron filter or chlorination/dechlorination treatment upstream of the Hydrologic system. This is rare but worth knowing if you see the symptoms; Hydrologic technical support can advise on the upstream configuration.

The high-iron well water trap

High-iron well water (above 0.3 ppm iron) fouls RO membranes quickly. The standard carbon pre-filter doesn't remove iron effectively; only KDF/catalytic carbon does. Growers on high-iron wells who skip the KDF upgrade replace their RO membrane within 6-12 months instead of the typical 2-3 years. The math: $40 KDF upgrade plus $90 annual KDF replacement is much cheaper than $90 RO membrane replacement every 6 months.

Stealth-RO 150 vs 300 vs Evolution-RO 1000 (The Decision)

The three Hydrologic systems most growers consider. Head-to-head.

The compressed comparison

• Stealth-RO 150 ($300): 150 GPD, single membrane, 98 percent contaminant removal, hobby through pro-sumer. Right for single 4x4 to 4x8 tent operations and growers who want the canonical cannabis-grade RO at the lowest entry price.
• Stealth-RO 300 ($450): 300 GPD, dual membrane, 98 percent removal, multi-tent hobby. Right for 5x5 tents, multi-tent setups, or single-tent operations where you want to fill reservoirs in half the time.
• Evolution-RO 1000 ($700): 1000 GPD tankless, 95 percent removal, light commercial. Right for 10+ light operations, greenhouses, multi-room hobby setups, or growers who want commercial flow rates without the HyperLogic price tier.

The capacity per dollar math

Cost per gallon-per-day of capacity:

• Stealth-RO 150: $2.00 per GPD
• Stealth-RO 300: $1.50 per GPD
• Evolution-RO 1000: $0.70 per GPD

Larger systems are dramatically cheaper per unit of capacity. This is one of the reasons commercial operations skip the Stealth line entirely and start at Evolution-RO 1000; the per-gallon economics improve substantially with scale.

The form factor difference

Stealth-RO 150 and 300 are wall-mountable, compact (roughly 18 x 16 x 6 inches for the 150; slightly larger for the 300), and look at home in a residential grow room. Evolution-RO 1000 is tankless (no holding tank needed), has higher flow rates (42 gallons per hour vs the Stealth's roughly 6 gallons per hour), and is sized for commercial racks or industrial-style installations rather than residential walls.

The contaminant removal difference

Stealth-RO removes 98 percent of contaminants. Evolution-RO 1000 removes 95 percent. The 3-percentage-point difference is small in practical terms (both produce water below 10 ppm starting from 500 ppm tap), but worth noting if you're working from extremely contaminated source water and need every percentage point.

The Pre-Evolution recommendation

Evolution-RO 1000 users producing more than 150 gallons per day or on hard water should pair the system with the Pre-Evolution High Capacity Pre-Filter ($120). The Pre-Evolution extends membrane life dramatically (replacement every 7,500 gallons instead of every 2,000). For commercial operations, this is essentially mandatory equipment.

The decision rules

Single 4x4 to 4x8 tent, residential setting: Stealth-RO 150.

Multi-tent hobby (2-3 tents) or single 5x5: Stealth-RO 300.

Light commercial (10+ lights, less than 1000 GPD demand): Evolution-RO 1000 with Pre-Evolution pre-filter.

Heavy commercial or industrial (1000+ GPD demand): HyperLogic Commercial or Industrial, custom-configured.

Hydrologic vs Growonix Head-to-Head

The only competitor that warrants a head-to-head comparison. Growonix is the other premium cannabis-grade RO brand most retailers carry alongside Hydrologic. The decision between them is genuine.

What they share

Both are premium cannabis-grade RO brands with 10+ years of grow community trust. Both ship at multiple GPD tiers (Growonix EX line covers 100 to 1000 GPD). Both are wall-mountable and serviceable. Both offer KDF/catalytic carbon upgrades for chloramines. Both have established accessory ecosystems. Both ship in roughly the same price range.

Where Hydrologic wins

Waste-water efficiency. Hydrologic's 1:1 flow restrictor (included in the box) is the best in the hydroponic category. Growonix runs 2:1 or 3:1 standard. For growers on metered water or water-conscious operations, Hydrologic's efficiency advantage compounds.

Replacement filter and membrane availability. Hydrologic parts are stocked at virtually every cannabis hydro retailer (Modern Farms, Hydrobuilder, HTG Supply, GrowGeneration, hundreds of independent shops). Growonix parts are stocked at fewer retailers and sometimes require manufacturer-direct orders. The serviceability gap matters when you're mid-cycle and need a replacement filter quickly.

Commercial scale. HyperLogic Commercial and Industrial lines scale to 28,800+ GPD. Growonix's commercial offerings top out lower.

Where Growonix wins

Larger replacement filter sizes. Growonix EX systems use 10-inch standard filter housings vs Hydrologic's compact form factor. Larger filters mean longer replacement intervals at the cost of larger physical footprint.

Build quality on the higher-tier units. Growonix's EX line uses heavier-gauge materials and metal brackets that Hydrologic's plastic-housing approach doesn't match. For commercial installations where the system gets bumped or vibration is a factor, Growonix's build quality matters.

Slightly higher contaminant rejection rates. Growonix EX rates 98-99 percent rejection on most units; Hydrologic Stealth-RO rates 98 percent and Evolution-RO 1000 rates 95 percent.

The decision rules

Want best-in-class waste-water efficiency, broadest replacement parts availability, and largest commercial scale options: Hydrologic.

Want highest build quality and longest filter replacement intervals at the cost of size: Growonix.

For most home and pro-sumer growers, Hydrologic is the canonical pick. For commercial operations that prioritize build quality over filter efficiency, Growonix is the legitimate alternative.

Cross-reference: our nutrient brand pillars (Athena, Heavy 16, HGV, Drip Hydro) all recommend Hydrologic Stealth-RO as the standard RO filter. The recommendation reflects the brand's combination of efficiency, parts availability, and grow community trust rather than a categorical superiority over Growonix.

The Cost Economics (Initial Purchase Plus 5-Year Operation)

The honest math on what an RO system costs over its operational lifetime.

Initial purchase

• Stealth-RO 150: $300
• Stealth-RO 300: $450
• Evolution-RO 1000: $700
• HyperLogic Commercial: $5,000-$25,000 (custom configuration)

Required upgrades for most growers

• ChloraShield or KDF/Catalytic Carbon Filter Upgrade: $40-60 one-time
• Pressure Booster Pump (if needed for low-pressure source): $180
• Float Valve for unattended fills: $25

Annual recurring costs

For a Stealth-RO 150 producing 30 gallons per day (typical 4x4 hobby grow):

• Replacement sediment filter (3x per year): $45
• Replacement carbon pre-filter or ChloraShield (every 2,000 gallons = roughly twice per year): $60-90
• Replacement RO membrane (every 2-3 years; amortized): $30-45 per year
• Total annual recurring: $135-180

5-year total cost of ownership

Stealth-RO 150 with KDF upgrade and basic accessories:

• Initial: $300 + $50 (KDF) + $25 (float valve) = $375
• 5 years of recurring: $135 × 5 = $675
• Total 5-year cost: $1,050
• Effective per-gallon cost over 5 years (54,000 gallons produced): $0.02 per gallon

For comparison, buying bottled RO water at a grocery store costs $0.50 to $1.00 per gallon. Distilled water at $1.50 per gallon. Even the cheapest delivery service runs $0.20+ per gallon. RO water filtration pays back its 5-year cost within the first few cycles of grow water consumption.

The cheap Amazon RO trap

A $100 Amazon RO system looks cheaper on the box. The real math: cheap RO systems use proprietary filter cartridges (not standard sizes), have shorter filter lifespans (typically 1-2 months vs Hydrologic's 2-4 months), have fixed 3:1 or 4:1 waste-water ratios (no efficiency option), and have lower-quality membranes that need replacement every 12-18 months. Over 5 years, the cheap RO costs roughly the same as Hydrologic but produces less water and requires more frequent replacement.

The serviceability gap matters more than the upfront cost. When your cheap RO breaks mid-cycle and replacement parts aren't available locally, your nutrient program is on hold until parts ship. Hydrologic parts are at every hydro shop; the breakdown is solved same-day.

The Case For and Against Hydrologic

The retailer-honest assessment.

Buy Hydrologic if

• You grow cannabis with premium nutrients (Athena, Heavy 16, HGV, Drip Hydro, House & Garden, CANNA). The published feed schedules require input water EC at or below 0.4 mS/cm; tap water above that throws off the math.
• Your tap water tests above 200 ppm (most US municipal water does). The mineral content interferes with nutrient ratios and creates calcium deposits in pots.
• You're on chloraminated city water and running biological inoculants (mycorrhizal products, beneficial bacteria, Heavy 16 Prime). Chloramines damage the microbes.
• You have well water with iron, sulfide, or hardness issues. Hydrologic's KDF upgrade handles these directly.
• You want a system that's serviceable locally with parts available at any hydro shop.
• You're planning to scale your grow. The lineup spans hobby through commercial without brand switching.

Skip Hydrologic if

• Your tap water already tests below 150 ppm and isn't chloraminated. Rare, but exists in some rural municipalities or near mountain water sources. In this case, a Tall Boy or Big Boy dechlorinator may be sufficient.
• You're growing organically in living soil with no nutrient salt program. Living soil tolerates tap water mineral content better than salt-based hydroponic systems.
• You only grow occasionally (one cycle every year or two) and can fill a reservoir with bottled distilled water without it being an operational burden.
• You're committed to a competing brand (Growonix specifically) for build quality or specific feature preferences.

The "but my plants seem fine on tap water" argument

Plants seem fine on tap water until the moment they're not. The visible effects of high-PPM tap water on cannabis (calcium deposits in pots, nutrient lockout in late flower, EC drift in reservoirs, reduced yields and terpene quality) compound slowly over multiple cycles. Many growers don't realize their tap water is the problem until they switch to RO water and see the improvement directly. If your nutrient brand publishes a feed schedule assuming input EC below 0.4, you're working against the brand's design until you provide clean input water.

Specific 2026 Product Picks

Modern Farms stocks the complete Hydrologic lineup. The recommended packages by grow scale.

The hobby cannabis kit (4x4 to 4x8 tent)

• Hydrologic Stealth-RO 150: $300
• ChloraShield Filter Upgrade (for city water) or KDF/Catalytic Carbon Upgrade (for well water): $40-60
• Float Valve for unattended reservoir fills: $25
• Initial replacement filter set (1 sediment + 1 carbon for first replacement): $40
• Total: approximately $410 for a 1-2 year setup

The multi-tent or pro-sumer kit (2-3 tents or 5x5)

• Hydrologic Stealth-RO 300: $450
• KDF/Catalytic Carbon Filter Upgrade: $50
• Float Valve: $25
• Pressure Booster Pump (if source water below 50 PSI): $180
• Initial replacement filter set: $50
• Total: approximately $755 with booster pump, $575 without

The light commercial kit (10+ lights)

• Hydrologic Evolution-RO 1000: $700
• Pre-Evolution High Capacity Pre-Filter: $120
• Float Valve: $25
• Pressure Booster Pump (recommended for any commercial setup): $180
• Pressure Regulator (for high-pressure municipal sources): $45
• Flowmaster Flow Meter: $30
• Initial replacement filter set: $80
• Total: approximately $1,180

The commercial scale

For 24+ light commercial operations or operations consuming 1000+ GPD: contact Modern Farms commercial accounts to scope a HyperLogic Commercial system based on your facility's water chemistry and production targets. HyperLogic systems are custom-configured per site, and the consultation is the first step.

Annual replacement parts

Budget for annual replacements regardless of which tier you bought:

• Replacement sediment filters (3 per year): $45
• Replacement carbon or KDF pre-filter (2 per year for ChloraShield, 1 per year for KDF): $60-90
• Replacement RO membrane (every 2-3 years): $90-180 amortized to $30-90 per year
• Total annual budget: $135-225 for Stealth-RO; higher for Evolution-RO and HyperLogic

Cross-reference: our Bluelab buyer's guide covers the meters that pair with any RO setup. Our nutrient brand pillars (Athena, Heavy 16, HGV, Drip Hydro) explain why RO water is foundational for premium feed schedules. Our 4x4 grow tent setup guide includes a Hydrologic Stealth-RO in the recommended hobby build.

Common Hydrologic Problems and Diagnostic Logic

"My RO system is producing less water than rated GPD"

Three checks in order. First, verify source water pressure (must be 50-80 PSI; low pressure means slow production); install a booster pump if needed. Second, verify source water temperature (cold water flows slower; well water at 50°F produces noticeably less than rated GPD compared to 70°F water). Third, check pre-filter clog status; pre-filters at 80%+ life produce visibly slower flow. Replace pre-filters on schedule (every 2-4 months) or earlier if you see flow drop.

"My RO water has higher pH than my source water"

Normal. The activated carbon pre-filter creates a temporary pH spike that mitigates over the first hours to weeks of system operation. New systems often show RO water at pH 7.5-9.0 for the first few days; this settles to 6.0-7.0 over time. The spike is harmless and mitigates without intervention.

"My RO water has lower pH than my source water"

Also normal. RO product water can have lower pH than feed water depending on dissolved CO2 levels in the source. The pH typically lands in 5.5-6.5 range for RO product water from typical municipal sources. Once you mix in calcium/magnesium supplements and nutrients, the final reservoir pH stabilizes; don't try to adjust the RO water itself.

"The RO membrane needs replacement after 8 months"

Two likely causes. First, chloramines passing through the standard carbon pre-filter (the most common cause; upgrade to ChloraShield or KDF). Second, high-iron well water without proper pre-filtration (iron fouls the membrane; KDF/catalytic carbon handles this). The standard membrane lifespan with proper pre-filtration is 2-3 years; early failure points to a pre-filtration gap, not a membrane defect.

"Pre-filters are clogging after only 1 month"

Source water has high sediment or biological load. Wells with sand or shallow drilling produce sediment that clogs carbon filters quickly. City water can have biological loads (especially during summer algae blooms) that clog filters. The fix: install an additional sediment pre-filter upstream of the Hydrologic system, or replace pre-filters more frequently (every 4-6 weeks vs 2-4 months).

"I'm storing my system for 3+ weeks; how should I prepare?"

RO membranes prefer constant water flow. For extended storage, flush the system with a 1:1 mix of RO water and food-grade glycerin to preserve the membrane and prevent biological growth. Hydrologic publishes specific storage guidance; consult the manual or call technical support before storing more than 3 weeks.

"Should I add CalMag to RO water before mixing nutrients?"

Depends on your nutrient brand. Athena Pro Line and HGV include calcium and magnesium in the base formula; no CalMag supplementation needed. Athena Blended, Heavy 16, House & Garden, and most other premium brands either include separate CaMg products or recommend supplementation with Botanicare CalMag Plus at 1-2 mL per gallon. The RO water itself is mineral-free; downstream supplementation in your nutrient mix is what matters, not adding CalMag to the RO before mixing.

Cross-reference: our EC and pH reservoir management pillar contains the complete diagnostic flowchart for reservoir problems across all RO setups and nutrient programs.

What We'd Tell You at the Counter

The honest summary, framed the way we'd say it in person.

If you're running premium cannabis nutrients on US municipal water above 200 ppm or any chloraminated source, you need RO filtration. The math of every premium feed schedule requires it. Hydrologic Stealth-RO 150 at $300 is the canonical pick for hobby grows; the ChloraShield or KDF upgrade is mandatory on city water (most US cities use chloramines).

Size your system one tier larger than the strict math says. The Stealth-RO 150 is the right pick for most 4x4 hobby tents because the math works at peak demand AND the system has headroom for grow expansion, hardening source water, and longer equipment life.

The waste-water ratio matters less than most growers think for cost (waste water in most home setups goes down the drain for free) and more than they think for environmental responsibility. Hydrologic's 1:1 restrictor option is included in the box; use it.

Replacement parts schedule matters more than people realize. Set calendar reminders for sediment filter every 3 months, carbon or KDF/ChloraShield every 6-12 months depending on type, and check RO membrane performance annually (test product water EC; if rising above 10-20 ppm from typical 0-5 ppm, the membrane is failing).

For commercial operations evaluating HyperLogic, the consultation process is the first step. Hydrologic configures HyperLogic systems based on your specific source water chemistry and production targets. Modern Farms commercial accounts can connect you with the Hydrologic technical team for the scoping conversation.

Don't substitute a $100 Amazon RO for a Hydrologic Stealth-RO 150 to save $200. The cost over 5 years is roughly the same; the difference is serviceability when something breaks mid-cycle. Hydrologic parts are at every hydro shop; cheap RO parts aren't.

The cluster of articles we've written reinforces this one. Every premium nutrient brand pillar (Athena, Heavy 16, HGV, Drip Hydro) recommends Hydrologic Stealth-RO as the foundational equipment. The EC and pH reservoir management guide covers the discipline that makes RO water valuable. The Bluelab buyer's guide covers the meters that monitor what you're producing. This pillar is the destination for those recommendations.

Modern Farms stocks the complete Hydrologic lineup: Stealth-RO 150 and 300, Evolution-RO 1000, Tall Boy and Big Boy dechlorinators, plus the full accessory ecosystem (ChloraShield and KDF filter upgrades, booster pumps, float valves, pressure regulators, replacement sediment and carbon filters, replacement membranes). Commercial accounts can scope HyperLogic Commercial and Industrial systems for larger operations. If you're shopping your first RO system, switching from a cheap Amazon unit, or scaling up from hobby to commercial, we're happy to help in person or by phone. We don't upsell.