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

Watts Premier WP531411 4-Stage Reverse Osmosis System

Starting our list is one of the top and most affordable under sink RO systems produced by Watts Premier, the WP531411 RO-Pure reverse osmosis system. It’s a standard system with basic RO filtration functions but lives up to Watts’s reputation by being able to eliminate a vast number of different kinds of contaminants for the lowest possible cost.

Filtration Process

The Watts Premier WP531411 RO system features 4 filtration stages consisting of two pre-filters, an RO membrane and a post-filter.

At the 1st stage, the water goes through a sediment pre-filter which traps particulates that are larger than 5 microns. It removes particles such as dirt, silt, sand and rust that may cause clogging in the later stages.

The 2nd stage of the system features of a 5-micron carbon block pre-filter that helps clear out chlorine, chloramines, most VOCs and any other chemicals that make the water smelly and taste unpleasant.

The 3rd stage is where everything gets going. It consists of a 0.0001-micron RO membrane which effectively filters out all the nasty contaminants from heavy metals like chromium, radium, lead and arsenic to harmful microorganisms like bacteria, virus and cysts. It also removes up to 98% of total dissolved solids and 97% of fluoride.

The final stage is a 5-micron carbon block post-filter which gives the water final polishing after leaving the storage tank. It helps to get rid of residual chlorine or any tastes and odors picked from the storage tank thereby ensuring the water coming out from the faucet is clean and tastes nice.

Filtration Capacity and Efficiency

The WP531411 system doesn’t have a high water output but it can give you a maximum of 50 gallons per day which is pretty the standard capacity of most small under sink RO systems. It should be absolutely sufficient for small to medium-sized households.

In terms of water efficiency, the system wastes around 3 gallons of water to produce one gallon of filtered water. It’s a bit high but just about the average ratio of similar types of RO systems.

The maximum pressure at which it can operate is 100 psi and it requires a minimum pressure of 40 psi to work effectively. If the feed water pressure is below 40 psi, then you will need a booster pump to achieve optimum performance.

Installation and Maintenance

If you are handy with tools, the Watts Premier WP531411 is pretty simple and straightforward to set up. All the necessary components are provided and it requires fewer tube connections, so it’s a matter just following the provided instructions precisely.

Filter and membrane changing is also extremely easy and fast. All it takes is pushing a button where the filter or membrane snaps out and you pull it out and replace it with the new one.

The two pre-filters require changing every 6 months and the post-filter every year while the membrane can last 2 to 5 years based on the quality of the water going into the system.

The other commendable thing about this unit is that it comes with an air gap RO faucet with an indicator that lets you know when it’s time to replace the filters. It turns red when the filters need changing and uses a long-lasting battery that can go up to one year. 

In addition, the unit has a slim, compact design which allows it to fit nicely in any under sink cabinet with minimal space requirements thereby leaving enough room for extra storage.

There are also check valves installed between each cartridge to prevent water and unwanted substances from flowing backwards. Plus the cartridges have double O-rings which as well help prevent leakages.

Generally speaking, there are no major downsides with this unit that we could point out. However, the drain saddle seems finicky. Other than that, everything else is up to standard.

If you working with a tight budget but still seeking a reliable and convenient basic under sink RO system, then this Watts Premier WP531411 model is a suitable pick for you.


  • Removes all kinds of contaminants from the water
  • Has a 50 GPD capacity which is sufficient for small and medium-sized families
  • Installation and filter changing is quick and simple
  • The faucet features an indicator to alert you when filters need changing
  • Slim and compact design that doesn’t take up much space
  • Comes with a 3-year limited warranty


  • The drain saddle is somewhat finicky
  • Wastes 3 gallons of water for each gallon purified water produced

Read moreWatts Premier WP531411 4-Stage Reverse Osmosis System

Watts Premier 531517 Pure Plus Reverse Osmosis System

Watts Premier 531517 Zero Pure Plus brings nothing but optimal efficiency and performance as far as water filtration is concerned. This is a newer model from Watts Premier and perhaps one of the first RO systems out there that’s designed with a complete water conservation feature.

It’s a combination of the superb functionality of the Watts Premier RO Pure Plus model and the water-saving ability of the patented Watts Premier ZeroWaste technology with the addition of a booster pump. For those struggling with regular low municipal water pressure, this may be just the right Watts Premier RO system for you.

Filtration Process

The 531517 Zero Pure Plus model like the RO Pure Plus employs a 4-stage water filtration process made up of two pre-filters, an RO membrane, and a carbon post-filter.

The first line of defense is a sediment filter which completely removes all suspended particles such as rust, dirt, silt, sand, and sediments from the incoming water down to 5-microns.

The 2nd stage uses a carbon pre-filter with also a 5-micron filtration capability and it quite effectively eliminates natural organic compounds and chemical contaminants like chlorine, VOCs and chloramines, as well as unpleasant tastes, odor, and particulates.

A TFC RO membrane with pores sized 0.0001 microns sits in the 3rd stage where its tiny pores provide a high rejection rate of about 98% which ultimately clears out more than 1000 different microscopic contaminants such as heavy metals, bacteria, viruses, cysts and also dissolved solids like calcium and sodium among many others.

The 4th and final stage is taken up by a special 1-micron VOC carbon post-filter which refines the filtered water by extracting any residual odors or taste residues from the RO tank. It as well helps remove any remaining chlorine, VOCs and other major contaminants missed by the RO membrane and the pre-filters like atrazine and MTBE’s giving you clean pure drinking water.

Booster Pump

Oneof the outstanding thing about this Zero Pure Plus model is that it comes incorporated with a booster pump which is a big bonus especially if your water source pressure is below the normal 60 psi municipal water pressure.

This useful device helps to increase the pressure of the water going into the system at the inlet. It can raise the pressure from as low as 40 psi or lower up to around 80 psi which not only boosts the performance of the system but also enhances its efficiency.

It does guarantee too much quality filtered water than when depending only on the municipal water pressure. Therefore, if you are struggling with low water pressure, then this is a feature you will no doubt appreciate.

Filtration Capacity and Efficiency

The 531517 Zero Pure Plus system is rated to produce 50 gallons of pure water a day which as we’ve mentioned several times above is sufficient to allow a small or fairly medium family to enjoy clean drinking water daily.

Now the major highlight of this Watts Premier RO unit is its exceptionally high water efficiency which is brought about by the patented ZeroWaste (R) design. This very innovative technology enables the system to return the wastewater it generates back into your home’s hot water supply.

This way no water is wasted making the system 100% efficient which is pretty commendable considering that most other similar RO systems waste up to 4 gallons or more for each gallon of pure water produced.

Installation and Maintenance

The unit is provided with every necessary thing you need to set it up and it can be typically installed by anyone that’s handy or at least has basic DIY skills.

It may, however, be somewhat tricky if there’s no existing power outlet where you planning to set it up as you will have to have one installed which may call for a plumber if you are not that handy. The pump requires a 110V electrical outlet that’s non-switched to power it up.

Changing the filters when performing maintenance is simple with each cartridge featuring a push button that allows the filters to easily snap out and be replaced by new ones.

Furthermore, the cartridges feature double O-rings to prevent leaking plus there are check valves installed between the elements to ensure no backflow of water into the system.

Even much better, the faucet it comes with has an indicator with a timer which keeps track of the filter life and lets you know when it’s time to change them by displaying a blinking red light.

You will have to replace the two pre-filters after every 6 months, the RO membrane once after 2 to 5 years and the post-filter after one year. The booster pump is relatively silent while running hence won’t cause any distractions while you are trying to have a conversation in the kitchen.

The downside with this unit is that even though it reduces the cost of water, it utilizes the pump to return the wastewater to the house which translates to additional energy cost compared to other RO systems with a booster pump. That’s the only major thing you will have to worry about.

In general, if your source water pressure is quite low or you are really concerned with the high wastewater rates of most RO systems, then we would very much recommend getting this Watts Premier 531517 Zero Pure Plus RO system.


  • Removes more than 1000 different contaminants
  • Feature a booster pump to enhance the system performance
  • Suitable for use in areas with low municipal water pressure
  • The ZeroWaste technology ensures 100% water efficiency
  • Decent production capacity of 50 gallons per day
  • Setting it up is fairly simple same as changing the filters
  • An indicator to inform you when it’s time to change filters
  • Comes with a 1-year limited warranty


  • Requires electricity which can make installation tricky for first-timers
  • The ZeroWaste technology may result in additional electricity cost

Read moreWatts Premier 531517 Pure Plus Reverse Osmosis System

Watts Premier 531417 RO Pure Plus Reverse Osmosis System

In the second position, we have the Watts Premier 531417 model which is another incredible standard under sink RO system from the company that offers an effective water filtration process. The unit is quite identical to the Watts Premier WP531411 model with the only differences being the faucet type and the special carbon block post-filter.

Filtration Process

Same as the WP531411 system, this Watts Premier 531417 model utilizes a 4-stage filtration process to clean and purify the water.

Stage 1 consists of a sediment pre-filter that clears out rust, sand, silt, dirt, coarse sand, scale and other suspended particles from the water down to 5 microns.

It’s followed by a 5-micron carbon block pre-filter in the 2nd stage which ensures a greater reduction of chemical contaminants especially chlorine, chloramines and other common chemicals that often cause unpleasant tastes and odor.

In the 3rd stage, the system uses a 0.0001-micron reverse osmosis membrane that’s capable of eliminating up to 98% of the remaining contaminants. It will clear out heavy metals, total dissolved solids, chemicals and microorganisms like cysts, viruses, and bacteria.

Stage 4 of the unit features a special VOC carbon block post-filter. This is a high-quality 1-micron filter that not only refines the water by removing residual tastes and odors from the tank but also helps further remove VOCs (volatile organic compounds) such as THMs, pesticides, and herbicides from the water making it cleaner and safer for drinking and cooking.

Filtration Capacity and Efficiency

At optimum feed water pressure which is 60 psi and above, this Watts Premier RO system can output up to 50 gallons of pure water in a day. It’s the same capacity as the WP531411 model and just enough to meet the demands of a small or medium-sized family.

With regards to efficiency, the Watts Premier 531417 wastes around 4 gallons of water to deliver a gallon of purified water.

It’s not really that efficient but with consistent high feed water pressure, the ratio can drop to 3:1. The system is designed to work with an incoming water pressure of between 40 to 80 psi.

Installation and Maintenance

You would break no sweat setting up this unit as the installation process is pretty simple and anyone with basic DIY skills can get it done under 2 hours.

It has a slim, space-saving design like its counterpart above, the WP531411 model hence it’s ideal for a small kitchen and will fit inside any under sink cabinet effortlessly.

Maintaining the unit is easy too. The filters and membrane cartridges are designed for quick changing. You simply press the filter, then twist it and pull it out. There are built-in check-valves installed in the manifold to ensure no messy or fussy change-outs.

The maximum life span of the two pre-filters is 6 months while the carbon post-filter can last for one year and the RO remembrance for 2 to 5 years.

This model is also equipped with a TDS sensor in the faucet with a red and blue LEDs indicator. It’s a nice bonus that will let you when it’s to change the filters to make sure the system maintains an optimum performance. 

Overall, aside from the slightly high wastewater to pure water ratio, the Watts Premier 531417 is a worthwhile alternative to the WP531411 model above for small homes or anyone looking for a highly affordable under sink RO system.


  • Adequate 4-stage RO filtration process
  • Suitable for small and medium-sized families
  • Simple installation process and maintenance
  • Slim design fits easily in most under-sink cabinets
  • TDS sensor indicates when it’s to change the filters
  • Highly affordable unit backed by a 3-year warranty


  • Slightly high wastewater to pure water ratio of 4:1
  • Doesn’t work efficiently with a feed water pressure of below 40 psi

Read moreWatts Premier 531417 RO Pure Plus Reverse Osmosis System

Watts Premier 500025 4SV 4-Stage Reverse Osmosis System

The Watts Premier 500025 is an awesome little under sink RO system. It’s the most affordable unit on our list and although it comes with a very simple filtration process, it will certainly give you clean and healthy drinking water.

Filtration Process

This Watts Premier 500025 model consists of the classic 4-stage RO filtration process which includes 3 filter cartridges: two pre-filters and a post-filter plus the main heart of the system which is the RO membrane.

Stage 1 comprises a sediment pre-filter which deals with the larger particles and sediments like sand, rust, and dust reducing them down to 5 microns.

Stage 2 is fitted with a 5-micron carbon block pre-filter which has a plethora of tiny pores that allow water to pass through while trapping a large amount of different chemical contaminants. It removes chlorine, volatile organic compounds, and chloramines which affect the color, odor, and taste of the water significantly.

The 3rd stage features the RO membrane which tackles all the remaining impurities that were not sieved by earlier stages. The very tiny 0.0001-micron pores on its surface trap up to 98% of the contaminants in the water including heavy metals, TDS,  cysts, bacteria, viruses, herbicides and many more.

Completing the filtration process in the 4th stage is a granular activated carbon (GAC) post-filter employed to provide the water with one final polishing by removing any possible taste and odor from the tank as well as any residual chlorine, leaving the water with a pleasant smell and a taste of purity.

Filtration Capacity and Efficiency

The RO membrane of the Watts Premier 500025 system has the capability to produce 50 gallons of pure water a day which should be able to cover an entire family of 4.

The system generates 4 gallons of wastewater for every gallon of pure water it produces and again like most of the other Watts Premier 4-stage systems, this ratio is a little on the high end compared to the average ratio of 3:1 seen in many standard under sink RO systems.

Installation and Maintenance

Having a simple compact design, the installation process of this Watts Premier model is rather easy provided you follow the instructions properly. All the necessary parts needed to set it up are provided and you just require basic tools to complete the process.

Maintenance is equally a breeze as it’s only the three filters that need changing periodically. The two pre-filters require replacing every 6 months and the post-filter every 12 months. The RO membrane can last 2 to 5 years before requiring changing.

Are there any downsides? Well, we couldn’t find any major setbacks other than that the system seems to make a continuous whistling sound due to the small hole it has at the base of its dispensing spigot.

All in all, the Watts Premier 500025 model will be appealing to anyone looking for a standard RO system that delivers a good level of performance with ease. The best part is that it’s so cost-effective which is another key reason we love it.


  • Capable of removing over 99% of contaminants
  • Produces 50 gallons a day ideal for small to medium families
  • Robust yet compact design that doesn’t take up much space
  • Installation and maintenance are straightforward
  • Comes at a highly affordable price with all parts included
  • Backed by a 3-year limited warranty


  • Water wastage is a bit high
  • May make whistling sound while running

Read moreWatts Premier 500025 4SV 4-Stage Reverse Osmosis System

Watts Premier WP500032 5-Stage Reverse Osmosis System

The Watts Premier WP500032 model is our top pick when it comes to 5-stage RO systems from Watts Premier. It’s a quality unit with excellent contaminant rejection rates and reliable performance at a pocket-friendly cost.

Filtration Process

The WP500032 RO system is equipped with 5 separate filtration stages that consist of three pre-filters, an RO membrane and a post-filter all which work together to deliver clean, crystal clear, purified drinking water.

The 1st stage is a sediment filter that removes all the suspended particles and sediments down to 5 microns which means essentially clears out any silt, dirt, rust, sand, scales and many other fine particulate matter present in the water.

The 2nd stage is made up of a 5-micron carbon block pre-filter which greatly reduces the amount of chlorine, chloramines and other common chemicals such as pesticides, herbicides and organic chemicals like VOCs.

The 3rd stage of the unit features another 5-micron carbon block pre-filter. This helps to further clear out chlorine, chloramines and harmful chemicals which may have slipped past the 2nd stage thereby effectively improving the taste and odor of the water.

At stage 4, the water passes through a 0.0001-micron RO membrane that works remarkably well to filter out over 98% of the contaminants from total dissolved solids to chromium, lead, copper, arsenic, cysts as well as dangerous microorganisms.

In the final stage, the unit uses a granular activated carbon (GAC) post-filter as the last polishing filter to remove any residual chlorine or other chemicals and also odors and tastes picked up while the water was sitting in the storage tank. The result is a thoroughly purified water that’s free of unpleasant taste and a wide of range of contaminants.

Filtration Capacity and Efficiency

This system like the other two models above comes with a standard RO membrane which is capable of producing a maximum of 50 gallons of filtered water per day. Therefore, it’s equally a good option if you have a small family as it will provide enough water to meet their daily use.

For each gallon of purified water it produces, the system generates around 4 gallons of wastewater, so it’s a little above average as far as efficiency is concerned but not different from most of the standard 5-stage under sink systems available in the market.

Installation and Maintenance

Setting the Watts Premier WP500032 model won’t present many challenges, that is, if you are handy or have some basic DIY skills. The installation manual clearly takes you through the whole process and the unit has a simple design that makes the process less stressful.

As for changing the filters, there’s little work involved since you only need to unscrew the filter bowls to remove the filter housings, then drop your replacement filters and screw back the bowls on the filter housings. It’s a simple process without much fuss.

The three pre-filters require changing every 6 months, the carbon post-filter every 12 months while the membrane should be replaced every 2 to 5 years.

If there is a setback to point out, it would probably be the relatively high wastewater ratio. Nonetheless, for a 5-stage under sink RO system that costs less than $300, it’s safe to say that the Watts Premier WP500032 is a worthwhile choice that can give you value for your money.


  • Clears out 99% of the contaminants in the water
  • A reliable system for cleaning municipal water with a high chlorine level
  • 50 GPD production capacity which is enough for small families
  • Easy to set up with basic DIY skills and changing the filters is simple too
  • A very pocket-friendly price tag with a long 3-year limited warranty


  • Wastes 4 gallons of water to generate a gallon of clean water
  • May require a booster pump for feed water pressure of below 40 psi

Read moreWatts Premier WP500032 5-Stage Reverse Osmosis System