RKIN Zero Installation Purifier vs Flash: Which Countertop or Under-Sink RO System Is Right for You?

Both the RKIN Zero Installation Purifier (Zero Installation Purifier) and the RKIN Flash deliver reverse osmosis-purified drinking water. Both remove lead, PFAS, fluoride, arsenic, and hundreds of other contaminants. Both are made by the same company with the same commitment to filtration quality.

So what is actually different? Installation, form factor, daily capacity, and how you use your kitchen.

Here is an honest side-by-side to help you pick the right one.

How Each System Works

The Zero Installation Purifier: Countertop, Zero Installation

The RKIN Zero Installation Purifier (Zero Installation Purifier) sits on your counter. You fill the bottom reservoir with tap water, press a button, and the system pushes water through its RO membrane into the top dispenser. No plumbing connection required.

• Fill, press, pour — that is the entire process
• Produces about half a gallon per cycle (roughly 10-15 minutes)
• Compact enough to fit on most kitchen counters
• Runs on electricity (plugs into a standard outlet)
• Perfect for renters or anyone who cannot modify plumbing

The Flash: Under-Sink, Dedicated Faucet

The RKIN Flash Undersink Reverse Osmosis System installs under your kitchen sink. It connects to your cold water line and delivers purified water through a separate, dedicated faucet mounted on your countertop or sink.

• Continuous, on-demand RO water — no filling or waiting
• Higher daily capacity than the Zero Installation Purifier
• Hidden under the sink — zero counter space used
• Requires a simple DIY installation (under an hour for most people)
• Ideal for homeowners who want a permanent, out-of-sight solution

Side-by-Side Comparison

Which One Fits Your Life?

Choose the Zero Installation Purifier if:

• You rent your home or apartment and cannot drill holes or modify plumbing
• You want something portable that moves with you
• Counter space is not a concern
• You like the ritual of filling and having a fresh batch of purified water ready
• You want the absolute simplest setup: unbox, fill, press go

Choose the Flash if:

• You own your home and want a permanent installation
• You value counter space and prefer a hidden system
• Your family uses a high volume of purified water daily (cooking, multiple people)
• You want on-demand, instant RO water without waiting for a batch cycle
• You are comfortable with a basic under-sink DIY install

Consider the U1 if you want more: If you want countertop convenience PLUS instant hot and cold water dispensing, the RKIN U1 4-in-1 Water Filter System combines RO filtration with a temperature-controlled dispenser. It is ideal for families who frequently make baby formula, tea, oatmeal, or anything requiring hot water — without boiling a kettle.

Pair Either One With Whole-House Protection

Neither the Zero Installation Purifier nor the Flash treats your shower, laundry, or appliance water. For complete home coverage, pair your chosen RO system with the RKIN OnliSoft Pro — a salt-free whole-house conditioner and carbon filter that prevents scale and removes chlorine from every tap.

Frequently Asked Questions

Is the Zero Installation Purifier's water quality the same as the Flash's? Yes. Both use reverse osmosis membranes that remove the same range of contaminants. Both include AlcaPure remineralization to add beneficial minerals back into the purified water. The difference is delivery method, not filtration quality.

Can I use the Zero Installation Purifier in an RV or vacation home? Yes. The Zero Installation Purifier is portable and only needs a power outlet and tap water. It is a popular choice for RVs, vacation rentals, and temporary living situations.

How loud is the Zero Installation Purifier while running? The Zero Installation Purifier has a small internal pump that runs during the purification cycle. It produces a quiet hum — roughly comparable to a countertop ice maker.

Does the Flash waste a lot of water? Modern RO systems like the Flash have significantly improved recovery rates compared to older designs. The Flash uses a permeate pump to minimize wastewater, making it one of the more efficient under-sink RO systems available.

Can I install the Flash myself? Yes. The Flash comes with all necessary fittings, tubing, and instructions. If you can connect a garden hose, you can install the Flash. The most involved step is drilling a small hole in the countertop or sink for the dedicated faucet.