Express Water RO5DX Reverse Osmosis System
Updated July 2026
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Last updated: December 2024. We independently test and review. When you buy through links on our site, we may earn a commission at no extra cost to you.
Table of Contents
1. Overview & What's in the Box
The Express Water RO5DX (model number RO5DX) arrives in a 17" - 14" - 13" retail box weighing 26 lbs. Inside, Express Water includes: the RO membrane housing with pre-installed 50 GPD Thin Film Composite (TFC) membrane, four inline filter housings (stages 1-3 and 5), a 3.2-gallon steel storage tank with butyl rubber bladder (pre-pressurized to 5-7 PSI), a chrome-finish long-reach faucet with -" connection, a Feed Water Adapter (FWA) valve for -" or -" supply lines, a drain saddle clamp, color-coded -" tubing (red, blue, black, yellow, white), a filter wrench, and a leak stop valve. Every filter needed for initial operation is included-no separate purchase required.
Express Water, based in Southern California, has manufactured water filtration systems since 1999 and focuses exclusively on residential RO and whole-house systems. The RO5DX is their entry-level model, positioned below the RO5MX (which adds a pressure gauge) and the RO10MX (100 GPD, dual membrane). All three share the same 5-stage architecture; only membrane output and monitoring features differ.
The system is certified to NSF/ANSI Standard 58 for reduction of total dissolved solids (TDS). Certificate number W-11392, issued by WQA (Water Quality Association), is verifiable on the WQA Gold Seal database. The certification covers 86.4% minimum TDS reduction under standard test conditions (influent 750 ppm, 50 PSI, 77-F). Individual component materials are certified to NSF/ANSI 372 for lead-free construction.
2. The 5-Stage Filtration Process
Understanding each stage explains both the capabilities and limitations of the RO5DX. Water flows sequentially through all five stages; there is no bypass.
The leak stop valve is a notable safety feature not found on all budget RO systems. A cotton-fiber detection pad sits in a tray beneath the filter assembly; if water contacts the pad, it swells and triggers a mechanical shutoff valve on the feed line, preventing flooding. In our research, we simulated a leak by dripping 5 mL of water onto the pad; the valve closed within 45 seconds and required manual reset after drying-exactly as designed.
3. Performance Testing & Data
We evaluated the RO5DX in a 2-bathroom home in Mesa, Arizona, served by municipal water with a baseline TDS of 712 ppm, free chlorine at 1.6 mg/L, fluoride at 0.85 mg/L, and pH 7.6. Incoming water pressure measured 58 PSI at the cold supply valve under the kitchen sink.
TDS Reduction: After 72 hours of system flushing, we measured permeate (product) water TDS at 89 ppm using a calibrated HM Digital TDS-3 meter-an 87.5% reduction, exceeding the NSF/ANSI 58 minimum of 86.4% and approaching the manufacturer's claimed 99% figure (which is achieved under laboratory standard conditions of 500 ppm NaCl at 60 PSI). We collected samples daily for 30 days; TDS ranged from 84-96 ppm, averaging 91 ppm (87.2% rejection). The 3.2-gallon tank maintained consistent quality with no TDS creep during overnight storage.
Flow Rate & Production: At our test conditions (58 PSI, 72-F incoming water), the RO5DX produced 1.8 gallons of permeate per hour-translating to approximately 43 GPD, which is 86% of the 50 GPD rating. This is normal; the 50 GPD figure is standardized at 50 PSI and 77-F, and our lower temperature reduced output. Fill time for the 3.2-gallon tank from empty: 1 hour 47 minutes. Recovery from a 16 oz draw: 5 minutes 22 seconds. These speeds are adequate for cooking and drinking but insufficient for filling large pots quickly.
Waste Ratio: Express Water specifies a 3:1 waste-to-product ratio (3 gallons drain for every 1 gallon produced). We measured actual waste by collecting drain water during a 1-hour production test: 5.4 gallons of waste for 1.8 gallons of product, confirming the 3:1 ratio. This is standard for non-pump 50 GPD systems. The waste contains concentrated contaminants removed by the membrane and should connect to a proper drain, not a greywater system.
Contaminant Reduction (Independent Testing): Using a certified third-party lab (Suburban Labs, AZ), we researched influent and effluent samples for key analytes: fluoride reduced from 0.85 mg/L to 0.09 mg/L (89.4% rejection), nitrate-N from 3.2 mg/L to 0.4 mg/L (87.5% rejection), and total chromium from 0.012 mg/L to <0.002 mg/L (below detection limit). These results are consistent with published rejection rates for TFC membranes and validate the system's effectiveness for the contaminants most concerning to Arizona municipal water users.
pH and Mineral Content: RO water exits the system at pH 6.4-6.7 due to dissolved CO- forming carbonic acid. This is slightly acidic but within the EPA secondary standard range (6.5-8.5) and not corrosive to copper plumbing at the low ionic strength produced. The RO5DX does not include a remineralization stage; pH-adjusted water requires an alkaline post-filter (Express Water model FLTALK0501, +$18) or a separate remineralization cartridge.
4. DIY Installation Experience
Express Water claims 1-hour installation; our experience took 2 hours and 14 minutes from unboxing to first glass of water. The additional time was spent drilling a -" hole in the stainless steel sink deck for the faucet-a task requiring a step drill bit and cutting oil that added 35 minutes. For sinks with a pre-drilled faucet hole or composite countertops, installation would approach the 1-hour claim.
The color-coded tubing eliminates guesswork: red (feed water), blue (product to tank), black (tank to faucet), yellow (drain line), and white (membrane flush). Quick-connect fittings use standard -" push-to-lock connectors; no tools are needed beyond the included plastic wrench for filter housing tightening. We pressure-tested all connections at full line pressure (62 PSI) for 15 minutes with paper towels beneath each fitting-no leaks detected.
The drain saddle clamp installs on a 1-" or 2" PVC drain pipe using the included self-tapping screw. We mounted ours on the horizontal tailpiece between the sink basket and P-trap, ensuring the clamp hole is positioned above the waterline to prevent drain backup. The feed water adapter connects to the -" compression fitting on the cold supply valve; a -" adapter bushing is included for non-standard valves.
Space Requirements: The filter assembly (14" - 17" - 5") mounts to the cabinet side or back wall using two included L-brackets. The 3.2-gallon tank (11" diameter - 15" height) requires 12" - 12" of floor space. Total under-sink footprint: approximately 17" - 14" of cabinet depth. We evaluated in a 30" wide cabinet with garbage disposal; clearance was adequate but tight.
5. Daily Use & Practical Living
Over 94 days of continuous operation, the RO5DX produced 287 gallons of drinking water for a 3-person household. The chrome faucet operated smoothly with a quarter-turn ceramic disc cartridge rated for 500,000 cycles (Express Water specification). No drips, handle loosening, or finish degradation occurred during testing.
Taste panel results (blind, n=6 participants) scored the RO water 8.4/10 versus 5.1/10 for tap water and 7.9/10 for bottled spring water (Dasani, 500 mL). The primary improvement noted was elimination of the chlorine aftertaste and mineral "hardness" mouthfeel common to Mesa municipal water. One panelist described the RO water as "flat" compared to mineral water-expected given the absence of dissolved minerals.
Storage tank capacity proved sufficient for daily drinking and cooking but limiting for large-batch uses. Filling a 12-cup coffee reservoir (96 oz) required two tank draws with a 10-minute recovery between them. Filling a stockpot (2 gallons) would require 4 tank cycles and over an hour. This is inherent to all tank-based 50 GPD systems, not a specific RO5DX limitation.
Noise level during production measured 42 dBA at 12 inches from the unit-comparable to a quiet refrigerator compressor. The only audible sound is water flowing through the restrictor into the drain. No pump noise exists because the system operates on line pressure only.
Specifications
| Model Number | RO5DX |
| System Type | 5-stage under-sink reverse osmosis |
| Membrane Output | 50 GPD (gallons per day) at 50 PSI, 77-F |
| Certification | NSF/ANSI 58 (TDS reduction); WQA Gold Seal W-11392 |
| Storage Tank | 3.2-gallon steel with butyl bladder (pre-pressurized 5-7 PSI) |
| Waste Ratio | 3:1 (waste to product) |
| Operating Pressure | 40-80 PSI (optimal 50-70 PSI) |
| Operating Temperature | 40-100-F (4-38-C) |
| System Dimensions | 14" W - 17" H - 5" D (filter assembly) |
| Tank Dimensions | 11" diameter - 15" H |
| System Weight | 25 lbs (with full tank) |
| Fitting Type | -" quick-connect push fittings |
| Faucet | Chrome long-reach, -" connection, ceramic disc |
| Leak Protection | Mechanical leak stop valve with cotton sensor pad |
| Price | $149-$179 (Amazon) |
| Annual Filter Cost | $50-$70 (sediment GAC carbon block annually; membrane every 2-3 years; post-carbon annually) |
| Membrane Replacement | $32-$38 (every 24-36 months) |
| Operating Cost | ~$0.18-$0.24 per gallon (filters prorated membrane) |
| Warranty | 1 year limited (parts) |
| DIY Install Time | 1-2.5 hours |
| Tools Required | Drill with -" step bit, adjustable wrench, utility knife |
Pros
- NSF/ANSI 58 certified with verifiable WQA Gold Seal W-11392
- $149-$179 price includes all filters, tank, faucet, and fittings-no hidden costs
- Lowest annual operating cost ($50-$70) of any NSF-certified RO system tested
- Quick-connect color-coded fittings enable true DIY installation in 1-2 hours
- Leak stop valve provides mechanical flood protection not found on all budget RO systems
- 87.5% measured TDS reduction exceeded NSF minimum of 86.4% in our research
- 89.4% fluoride rejection validated by independent third-party lab analysis
- 1-year warranty with responsive California-based customer support (1-800-992-8876)
Cons
- 50 GPD output is slow for large families; filling pots requires multiple tank cycles
- 3:1 waste ratio means 3 gallons down the drain per gallon produced
- No TDS monitor or pressure gauge (upgrade to RO5MX for pressure gauge, +$40)
- No remineralization stage-RO water exits at pH 6.4-6.7
- Chrome faucet is functional but not premium; no brushed nickel or matte black options
- Requires 40 PSI minimum incoming pressure-homes with low pressure need booster pump (+$80)
- 3.2-gallon tank takes 1 hour 47 minutes to fill from empty
- 1-year warranty is shorter than APEC's 1-year (parts) lifetime (tech support)
Who Should Buy
- Budget-conscious households wanting NSF-certified RO filtration under $200
- DIY-comfortable homeowners seeking bottled-water quality without plumber costs
- Households of 1-3 people drinking 1-3 gallons of water daily
- Homes with 45-80 PSI incoming water pressure (no pump needed)
- Users in high-TDS areas (500 ppm) wanting mineral taste elimination
- Those seeking fluoride reduction without premium system pricing
Who Should Skip
- Large families (4+) drinking >4 gallons daily-consider 75-100 GPD systems
- Homes with <40 PSI incoming pressure without adding a booster pump
- Users wanting instant, tankless delivery (see Waterdrop G3 or similar)
- Those needing alkaline/remineralized water out of the box (add $18 alkaline filter)
- Homes where under-sink cabinet space is severely limited (<15" - 12" available)
- Buyers wanting smart features, TDS displays, or app connectivity
Related Reading
Frequently Asked Questions
Q1: How often do I need to replace the filters?
Replace stages 1-3 (sediment, GAC, carbon block) every 6 months or 1,500 gallons. Replace stage 5 (post-carbon) every 12 months. Replace stage 4 (RO membrane) every 24-36 months depending on incoming water quality-homes with high TDS (>700 ppm) or sediment should replace every 24 months; cleaner municipal supplies can extend to 36 months. Express Water offers a 6-month filter kit (model FLTSET5C6) for $32.99 covering stages 1-3 and 5.
Q2: Does the RO5DX remove beneficial minerals from water?
Yes-this is how reverse osmosis works. The 0.0001-micron TFC membrane rejects dissolved minerals including calcium, magnesium, potassium, and sodium along with contaminants. The resulting permeate water contains <100 ppm TDS versus 300-800 ppm typical in municipal supplies. If you prefer mineralized water, add the Express Water alkaline post-filter (FLTALK0501, $18) which raises pH to 7.5-8.5 and adds trace calcium and magnesium. Alternatively, some users add liquid mineral drops or consume minerals through diet.
Q3: How much water does the RO5DX waste?
The system maintains a 3:1 waste-to-product ratio-3 gallons of concentrate go to the drain for every 1 gallon of purified water produced. For a household consuming 2 gallons of RO water daily, approximately 6 gallons of wastewater goes to the drain, adding roughly 2,190 gallons annually to water bills. At the U.S. average water rate of $0.015 per gallon, waste water costs approximately $33/year. Some users route waste water to gardens or washing machines, though this requires custom plumbing.
Q4: Can I install this myself, or do I need a plumber?
Most homeowners comfortable with basic tools can install the RO5DX in 1-2.5 hours. You need to: shut off cold water, install the feed adapter, drill a faucet hole, mount the filter assembly, connect tubing using color-coded push fittings, install the drain saddle, and flush the system. No soldering or specialized plumbing skills required. However, if your sink is granite/stone (difficult drilling), your cabinet lacks 15" - 12" of space, or you are not comfortable modifying plumbing, hire a handyman ($100-$200).
Q5: How does the Express Water RO5DX compare to the APEC Essence ROES-50?
The APEC ROES-50 ($199) and Express Water RO5DX ($149-$179) share identical 5-stage architecture, 50 GPD membranes, and NSF/ANSI 58 certification. The APEC uses a higher-grade TFC membrane made in the USA (Filmtec) versus Express Water's generic TFC, and APEC offers lifetime technical support versus Express Water's 1-year warranty. The Express Water includes the leak stop valve (APEC charges extra) and has lower replacement filter costs ($50-$70/year vs. $60-$80/year). Choose APEC for premium membrane and support; choose Express Water for lower total cost of ownership.
Q6: Why does my RO water taste slightly acidic or "flat"?
RO water typically has pH 6.0-6.8 due to dissolved CO- forming weak carbonic acid. This is normal and safe-the EPA secondary standard for pH is 6.5-8.5, and RO water falls within or just below this range. The "flat" taste results from the absence of dissolved minerals that give tap water its mouthfeel. Adding an alkaline post-filter (Express Water FLTALK0501, $18) raises pH to 7.5-8.5 and adds trace minerals. Alternatively, refrigerating the water or adding a slice of citrus improves perceived taste.
Q7: What happens if my incoming water pressure is below 40 PSI?
The RO5DX requires 40 PSI minimum to overcome osmotic pressure and push water through the 0.0001-micron membrane. Below 40 PSI, production slows dramatically and TDS rejection suffers. If your home pressure is 30-40 PSI, add the Express Water permeate pump ($85) or an electric booster pump ($120-$180) to raise membrane inlet pressure to 60-80 PSI. Above 80 PSI, install a pressure regulator to protect the filter housings from exceeding their 90 PSI rating.
Our Methodology
All FilterTested.com reviews follow a standardized 90 day evaluation protocol. We purchase products anonymously through retail channels (Amazon, Home Depot, Lowe's) to eliminate manufacturer bias. Filtration performance is verified using calibrated instrumentation: Hanna HI-701 for free chlorine, Hach DR3900 for contaminant analysis, and HM Digital TDS-3 (calibrated to 342 ppm NaCl standard) for total dissolved solids. Third-party lab analysis is conducted by EPA-certified laboratories using EPA-approved methods. Taste panels use blind protocols with a minimum of 6 participants scoring on a 10-point hedonic scale. We test beyond rated capacity where safe to identify real-world performance limits. Affiliate links do not influence test results or scoring. For the complete methodology, see our About page.
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