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

Read moreWatts Premier 521934 Six Stage Reverse Osmosis System

Watts Premier 0950045 ZeroWaste Reverse Osmosis System

The Watts Premier 0950045 is yet another super-efficient RO system produced by Watts Premier featuring their innovative ZeroWaste technology.

In addition to this, the unit is incorporated with a booster pump and can achieve purification standards comparable with the Watts Premier 531517 Zero Pure Plus model above which makes a great alternative for those who experience issues with water pressure.

Filtration Process

The filtration process of this Watts Premier 0950045 RO system is made up of 4 separate stages that extract a wide range of contaminants from the water to ensure it’s clean and much safer for drinking and cooking.

The first two stages consist of a 5-micron sediment pre-filter in the 1st stage and an equally 5-micron carbon block pre-filter in the 2nd stage.

These two pre-filters together help clear out sediments and fine particles suspended in the water as well as chemical contaminants like chlorine, chloramines and VOCs which lead to bad taste and odor.

The RO membrane takes up the 3rd stage of the system and it deals with the remaining microscopic contaminants from TDS to heavy metals and microorganisms removing up 98% of them down to 0.0001 microns.

The last stage includes a quality granular activated carbon (GAC) post-filter that’s installed right after the storage tank.

Here, the water undergoes one final polishing where any chlorine or other chemicals that slipped past the RO membrane are completely removed. Unpleasant tastes or odor collected from the RO tank are also removed before the water is dispensed.

Booster Pump

To facilitate a consistently high level of filtration and performance, Watts Premier has included a booster pump in this Watts Premier 0950045 model. The pump is capable of raising the pressure of the water entering the system from below 40 psi up to 80 psi.

In doing so, it enables the system to perform at its peak which is one of the reasons that makes this model another wonderful option for use in areas that usually face very low or fluctuating water pressure.

Filtration Capacity and Efficiency

The production rate of the Watts Premier 0950045 is only 24 gallons per day and this is the area that it falls short compared to other models on this list. It’s a pretty low capacity considering that most standard systems offer an average output of 50 gallons of filtered water a day.

However, if you are intending to produce purified water for less than three people, then 24 gallons per day may be enough, that is if they don’t use a lot of water regularly.

Again similar to Zero Pure Plus model, the distinct feature that makes this unit stand out is none other than the ZeroWaste technology.

The system does not send the wastewater down the drain but instead returns it into the house hot water supply where it can be reused somewhere else like washing the car or cropping the lawn.

In other words, while some wastewater is generated, literally nothing goes to waste in the production of the pure water hence making the system 100% efficient.

Installation and Maintenance

Installing the unit by yourself is not hard at all provided you have some basic technical skills because the pump requires electricity which means you will need to have a power outlet installed where you will be putting the system in case you don’t already have one in place.

As for maintenance, you will need to change the pre-filters every 6 months and the post-filter every year. The RO membrane has a lifespan of 2 to 5 years, so it can last a while before requiring changing depending on the condition of your incoming water.

The only drawback is that besides boosting the water pressure at the inlet, the pump is used by the ZeroWaste technology to pump the wastewater back to the house hot water line. This results in additional energy use which may lead to an increase in your monthly electricity bill.

The pump does make a little sound while running but it’s not that loud to be noticeable over a normal conversation.

Overall, Watts Premier 0950045 provides reliable performance and superb water efficiency. If you don’t mind the low production rate and using a bit more electricity, this is another good system to consider, particularly if your source water is pressure is a major issue.


  • Reliable performance in removing contaminants
  • Booster pump helps raise the water pressure
  • High water efficiency thanks to the ZeroWaste technology
  • Relatively easy to install with basic technical skills
  • Backed by a 1-year limited warranty


  • Low production capacity of only 24 gallons a day
  • Uses a bit more electricity than other RO systems

Read moreWatts Premier 0950045 ZeroWaste Reverse Osmosis System

Whirlpool WHER25 Reverse Osmosis System [3-Stage]

If your water usage is not that high or you are living alone but still want to ensure your drinking water is properly purified, then the Whirlpool WHER25 will most probably be a perfect choice for you. It’s a really affordable unit, but still quite efficient at cleaning the water.

Despite being a 3-stage filtration system, this reverse osmosis system performs really well. It has the mandatory three filters needed to remove numerous unhealthy contaminants such as chemicals, sediments, arsenic, lead, dissolved solids, chlorine odor and taste and many more.  

It offers very decent performance for a unit of its size and price. It will definitely deliver pure, fresh water. You will not get large quantities of water from this unit either, but if your water demand is on the lower side, then you have nothing much to worry about.

The unit can produce around 14 gallons a day which is just enough to cater to the daily drinking and cooking needs of a family of 4. However, in comparison to its water wastage ratio which is 3 gallons of wastewater for one gallon of pure water, this Whirlpool isn’t that efficient when it comes to water wastage.

You can easily change the filters without any hassles or mess. No need of opening anything, it just needs a quarter turn and you have access to the cartridges for replacement.

The pre and post-filters need to be changed every 6 months while the membrane should be changed every 2 years. That’s a pretty decent life span for such an affordable unit. Plus it comes with a built-in filter change indicator that will prompt you when the filters need replacement.

The Whirlpool WHER25 comes ready for installation with a DIY instruction manual to guide you through the whole process. The manufacturer also provides lifetime technical support, so should you have any difficulties while setting it up, you can seek their assistance.

Generally, this Whirlpool model is not a heavy-duty system, but for the price, it’s a fair budget solution. It will most probably meet the needs of any small family out there.


  • Convenient and efficient for a small family
  • Long-lasting RO membrane
  • An indicator to prompt you when the filter needs replacement
  • Easy to set up and maintain
  • Very affordable price


  • You may need to get additional filters like remineralization filter
  • Not ideal for more than 4 people
  • Water wastage is a bit high with regards to the flow rate

Read moreWhirlpool WHER25 Reverse Osmosis System [3-Stage]