Watts Premier 521934 Six Stage Reverse Osmosis System

Concerning filtration performance and production rate, the Watts Premier 521934 model takes the upper hand compared to the rest of Watts Premier RO systems featured on our list. This unit is a top performer offering a very fast production rate and remarkable filtration process designed to ensure the purified water generated is of high quality.

Filtration Process

The Watts Premier 521934 has 6 stages of filtration consisting of three pre-filters, two parallel flow membranes and a post-filter all working together to make sure the water is thoroughly purified.

The 1st stage is a 5-micron sediment filter that traps the fine particles and larger sediments such as dirt and sand to protect later filters from getting clogged. 

It’s followed by a 5-micron carbon block filter made from coconut shell in the 2nd stage which is the first point where chlorine and other chemical contaminants like chloramines and VOCs are extracted from the water.

The water then goes through a second 5-micron carbon block filter in the 3rd stage also made from coconut shell and this provides additional reduction of the remaining chlorine and chemicals while as well acting as the pre-filter to the RO membranes.

The 4th and 5th stages feature two parallel flow RO membranes which allow the system to perform double filtration. This one of the features that make the Watts Premier 521934 a highly effective water purification system.

These quality membranes filter the water down to 0.0001 of a micron basically removing 99% of the contaminants which includes TDS, microorganisms, heavy metals and natural organic compounds.

Taking the 6th is a granular activated carbon (GAC) post-filter which is the final stage in the system and serves as the last polishing filter right after the water leaves the storage tank. It clears out any residual chlorine, tastes or odor in the water before it’s dispensed out of the faucet.

Filtration Capacity and Efficiency

The best part that puts this Watts Premier 521934 model ahead of the rest is the exceptionally fast production rate it offers especially since it’s a standard under sink reverse osmosis system.

The two parallel RO membranes each produce up to 75 gallons of purified water per day which is not only an adequate capacity for those who use large amounts of water regularly but provides a much faster water production rate than RO systems that utilize only one 150GPD RO membrane.

Having a single filter is good, but two is much better because it translates to faster purification times as well as a more continuous flow of water plus the unit comes with a large, space-efficient 4-gallon RO storage tank offering more than enough capacity to ensure a regular supply of water.

This is a perfect unit for large families as well as corporate environments like offices or small businesses. It can comfortably handle pressures of up to 150 psi.

Installation and Maintenance

The process of setting up this high-performance Watts Premier model is fairly easy if you have some basic DIY skills. You just need to follow every step in the installation manual dutifully and you will it up and ready to run in less than 2 hours.

The two parallel membranes will give you a service life of 2 to 5 years. For the pre-filters, you will need to change them after every 6 months and the post-carbon filter once every year.

To sum it all, Watts Premier 521934 is a unit that offers great value for money. It’s not only a highly effective water purification system due to its double filtration but it also comes at an incredibly reasonable cost. You will certainly not be disappointed if you have a large family.


  • Double membrane design for optimum filtration performance
  • Very fast production rate with adequate capacity for larger families
  • Big 4-gallon holding tank facilitates a constant supply of purified water
  • Setting it up is fairly easy as well as changing the filters
  • Backed by a 1-year limited warranty


  • May not work well in areas with low feed water pressure

Product Overview

ProductWatts Premier 521934 Six Stage Reverse Osmosis System
BrandWatts Premier
Rating3.3 out of 5 stars (3.3 / 5) (More than 5 reviews)
Recommended price249 USD (Check the latest price at Amazon.com)

Product Specifications

Pre-filtersStage 1: 5 Micron Sediment Filter
Stage 2 & 3: 5 Micron coconut shell carbon block filter
RO membraneStage 4 & 5: 2 parallel flow RO membranes
Post-filtersStage 6: High-quality In-Line Granular Activated Carbon (GAC) Final Polishing Filter
Incoming Water Pressure40-80 PSI
Storage tank3-gallon capacity
Fitting adaptors3/8” Stem & 1/4” Quick connect fitting adapter
Filtered Water to Waste Water Ratio1:5
Alkaline / pH+ RemineralizationNo
UV FilterNo
Booster PumpNo
– WQA Gold seal
– NSF/ANSI 372 Lead Free
DocumentsUser Manual [PDF]
Warranty [PDF]




Installation Guide

This video shows you step-to-step how to install Watts Premier 5-Stage Reverse Osmosis System.



Are the components BPA free?

No, it doesn’t, the pump is used for creating more pressure at the water inlet, not at the outlet or storage tank.


Images Gallery

Watts Premier 521934 6-Stage Reverse Osmosis System

Watts Premier 521934 6-Stage Reverse Osmosis System

Watts Premier 521934 - Faucet
Watts Premier 521934 – Faucet
Watts Premier 521934 - Connector
Watts Premier 521934 – Connector

Watts Premier 521934 - Components diagram
Watts Premier 521934 – Components diagram

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