Which RKIN Water Filter Is Right for You? Zero Installation Purifier, Flash, U1, and OnliSoft Compared
Share
The most common question we hear: “I want cleaner water. Which one should I get?”
The honest answer is: it depends on what problem you’re solving. A renter in Chicago with chlorine concerns has a different need than a homeowner in Phoenix dealing with hard water and lead pipes. Picking the wrong product means spending money on features you don’t need or not solving the problem that matters.
This guide matches your situation to the right product.
Start Here: What’s Your Primary Problem?
- → My drinking water tastes or smells bad (chlorine, metallic, musty)
- → I want to remove PFAS, nitrates, or lead from my drinking water
- → I have scale buildup on fixtures, stiff laundry, skin/hair issues
- → I want everything — clean drinking water AND whole-house treatment
Each of these points to a different product. Let’s walk through them.
Problem 1: Bad Taste or Contaminants in Drinking Water (No Installation)
Best match: RKIN Zero Installation Purifier
The Zero Installation Purifier is RKIN’s countertop RO system. It sits on your counter, requires no plumbing, and filters water through a multi-stage process: sediment, carbon block, RO membrane, and your choice of post-filter — AlcaPure (adds calcium and magnesium minerals back for alkaline 7–8 pH water) or OnliPure (reduces TDS to near zero for lab-grade purity).
What it solves: - Chlorine taste and odor - PFAS and forever chemicals - Lead and heavy metals - Nitrates and agricultural runoff - TDS (total dissolved solids) - Fluoride (high-concentration removal)
Who it’s for: - Renters who can’t modify plumbing - Anyone who moves frequently - Single person or couple with moderate daily water use - Budget-conscious households that want RO quality at the lowest entry price
What it doesn’t do: - Treat whole-house water (shower, laundry, appliances) - Provide hot water on demand - Deliver high-volume output for large families
→ See the RKIN Zero Installation Purifier
Problem 2: Clean Drinking Water + Features (No Installation)
Best match: RKIN U1 4-in-1 Water Filter System
The U1 is a full countertop water station. It combines RO filtration with instant hot and cold water dispensing, UV sterilization, hydrogen infusion, and alkaline remineralization — all without touching a pipe.
What it solves: Everything the Zero Installation Purifier handles, plus: - Instant hot water (up to 200°F) — replaces a kettle and a filter - Chilled water (down to 59°F) — replaces a filtered pitcher in the fridge - UV sterilization — kills bacteria and viruses the RO membrane can’t catch - Hydrogen-rich water — for health-focused users
Who it’s for: - Households that want one countertop appliance handling filtration, hot water, and cold water - Health-focused buyers who want the full stack (UV + hydrogen + alkaline) - Families who use a lot of filtered water for cooking, tea, coffee, and drinking - Renters or homeowners who want a portable, no-plumbing solution
What it doesn’t do: - Treat whole-house water - Replace a whole-house filtration system for pipes/appliances
→ See the RKIN U1 4-in-1 Water Filter System
Problem 3: Clean Drinking Water + Permanent High-Volume Supply
Best match: RKIN Flash Undersink RO System
The Flash connects to your cold water line under the sink and delivers filtered water on demand through a separate, dedicated faucet. It produces 75 gallons per day — enough for a family of four with water to spare. Like the Zero Installation Purifier, the Flash comes in two editions: AlcaPure (alkaline mineral water) and OnliPure (zero TDS purity).
What it solves: - Same contaminant removal as the Zero Installation Purifier and U1 (nitrates, PFAS, lead, chlorine, fluoride) - High daily volume without manual tank refilling - Hands-off operation — filter and forget
Who it’s for: - Homeowners who want a permanent, low-maintenance drinking water solution - Families of three or more who consume a lot of filtered water - Anyone who cooks daily and needs consistent volume for pasta, soups, coffee - Long-term renters with landlord permission for minor plumbing work
What it doesn’t do: - Provide hot or cold water on demand - Work without plumbing installation - Move with you when you leave
→ See the RKIN Flash Undersink RO
Problem 4: Scale, Skin/Hair Issues, and Whole-House Water Quality
Best match: RKIN OnliSoft Pro — Salt-Free Conditioner + Carbon Filtration
If your problem is hard water damage (scale on fixtures and appliances, stiff laundry, dry skin and hair) combined with chlorine and chemical disinfectants throughout your home, the OnliSoft Pro addresses both in one system.
It uses template-assisted crystallization (TAC) to prevent scale without salt or chemicals, paired with activated carbon filtration to remove chlorine, chloramines, and disinfection byproducts from every tap in the house.
What it solves: - Scale buildup on pipes, water heaters, dishwashers, shower heads - Chlorine and chloramine removal from shower, bath, laundry, and kitchen tap - Dry skin and hair from combined hard water and chemical disinfectant exposure - Maintenance headaches from traditional salt-based softeners (no salt, no brine tank)
Who it’s for: - Homeowners with moderate-to-high hardness and municipal water - Anyone whose primary concern is whole-house water quality (not just drinking water) - People switching away from salt-based softeners due to maintenance fatigue or sodium concerns
What it doesn’t do: - Remove nitrates, PFAS, lead, or fluoride from drinking water (add a Zero Installation Purifier or U1 for that) - Fully “soften” water the way an ion-exchange salt softener does (minerals remain but don’t stick)
Other whole-house options worth considering: - RKIN Salt-Based Water Softener — if you want traditional full mineral removal and the classic “soft water” feel - Salt-Free Whole-House Conditioner (base model) — scale prevention without the carbon filtration stage - RKIN OP1L Whole House Filter — certified for lead, cyst, PFOA, and PFOS removal at the whole-house level (protects every tap, not just drinking water) - RKIN Dragon Spin-Down Sediment Filter — self-rinsing pre-filter for heavy sediment (ideal as the first line of defense for well water or high-particulate municipal water)
→ See the RKIN OnliSoft Pro — Salt-Free + Carbon Combo
Quick Reference: Match Your Situation
| Situation | Best Product | Why |
|---|---|---|
| Renter, bad taste/smell | Zero Installation Purifier | Zero installation, portable, full RO |
| Renter wanting hot + cold water | U1 | No plumbing, hot/cold/filtered in one |
| Homeowner, high daily volume | Flash | 75 GPD, hands-off, permanent |
| Hard water + chlorine (whole house) | OnliSoft Pro | Conditions + carbon, no salt needed |
| Want both: whole-house + drinking water | OnliSoft Pro + Zero Installation Purifier/U1 | Full coverage, each solving different problem |
| Well water with bacteria | UV Water Disinfection System + any RO | UV kills bacteria/viruses, RO removes contaminants |
| Lead or PFAS at every tap | OP1L | Certified whole-house lead, PFOA/PFOS removal |
| Heavy sediment (well or old pipes) | Dragon + any system | Self-rinsing pre-filter protects downstream equipment |
| Nitrates (Midwest/agricultural area) | Flash or Zero Installation Purifier | RO is the only reliable residential nitrate removal |
| Moving frequently | Zero Installation Purifier or U1 | Both fully portable, no installation |
When to Use Two Systems Together
Some homes need both whole-house treatment and point-of-use RO. The most common setup:
OnliSoft Pro (whole-house) + Zero Installation Purifier or U1 (drinking water)
The OnliSoft Pro handles scale protection and chlorine removal for the entire house. The Zero Installation Purifier or U1 adds RO filtration for the water you actually drink and cook with — removing nitrates, PFAS, and lead that carbon alone doesn’t catch.
For homes with heavy sediment or well water, adding a Dragon Spin-Down Sediment Filter as the first point of entry protects everything downstream.
For homes where lead or PFAS in the water supply is a concern at every faucet (not just the kitchen), the OP1L Whole House Filter provides certified removal at the point of entry.
This is the closest you can get to completely addressed water at every point of use without the cost and maintenance of a whole-house RO system.
Frequently Asked Questions
What is the difference between the Zero Installation Purifier and the U1?
Both are countertop RO systems with no installation. The Zero Installation Purifier is the entry-level option focused on pure RO filtration with your choice of AlcaPure (alkaline) or OnliPure (zero TDS) post-filter. The U1 adds instant hot water (200°F), cold water (59°F), UV sterilization, and hydrogen infusion on top of full RO filtration. Check rkin.com for current pricing on both models.
Does the OnliSoft Pro replace a water softener?
It depends. The OnliSoft Pro prevents scale without removing hardness minerals — it changes how minerals behave so they don’t stick to pipes and surfaces. Traditional ion-exchange softeners remove hardness minerals entirely, which produces a noticeably different “soft water” feel. If your main concern is protecting appliances and pipes, the OnliSoft Pro handles it. If you want the classic soft-water feel, RKIN also makes a salt-based water softener.
Which system removes PFAS?
All three RO systems — the Zero Installation Purifier, U1, and Flash — remove PFAS at the RO membrane stage (95%+ removal). The OnliSoft Pro’s carbon filtration reduces PFAS but at lower rates. For certified whole-house PFAS removal, the OP1L is designed specifically for lead, cyst, PFOA, and PFOS reduction at every tap.
Can I use the Zero Installation Purifier or U1 if I have well water?
Yes, with a note: well water with bacterial contamination needs UV disinfection. RKIN’s Stainless Steel UV Water Disinfection System is purpose-built for this — it kills bacteria and viruses before water reaches your RO system. Pair it with any RKIN RO system (Zero Installation Purifier, U1, or Flash) for complete well water treatment. For well water with heavy sediment, adding a Dragon Spin-Down Sediment Filter before your UV and RO systems will extend filter life significantly.
What is the best RKIN system for a family of four?
The Flash Undersink RO provides 75 gallons per day — ample for a family of four. For whole-house hardness and chlorine, add the OnliSoft Pro. For drinking water only without installation, the U1 can serve a larger household with its hot and cold dispensing features.
What are the AlcaPure and OnliPure editions?
The Zero Installation Purifier and Flash both come in two editions based on the post-filter. The AlcaPure edition adds calcium and magnesium minerals back into the purified water for an alkaline taste (7–8 pH), similar to spring water. The OnliPure edition reduces TDS to near zero for lab-grade purity, similar to distilled water. You can switch between editions at any time by ordering a different post-filter.
RKIN has been making clean water accessible to American families since 2009. All systems ship free within the Continental US and are backed by a satisfaction guarantee. Questions? Call 1-800-803-4551 or live chat Mon–Fri, 9 AM–5 PM EST.
