• A compact design – saving your space
  • A modular design – easy for filter changing
  • Easy to install
  • Includes a faucet and a 3-gallon water storage tank
  • Certified by WQA to NSF/ANSI 372

The Watts Premier WP531411 4-Stage Reverse Osmosis System has a modular design, and as an under sink water filter, it is able to produce up to 50 gallons of pure water every day. Well, it offers 50 gallons at 60 psi and 77 degrees Fahrenheit. If the water pressure or temperature of the feed water varies, the result will be different. Low temperature and lower pressure result in less pure water it will produce every day.

This RO system comes with a LED indicator in its faucet. When the filters wear out, the indicator will remind you that you need to replace them. This feature is useful, because you don’t need to guess when to do that. And you don’t need to buy a TDS meter to measure yourself on a regular basis.

This system has 4 stages, which can offer you pure water. These stages include:

  • In stage 1, a 5-micron sediment filter is used to reduce or remove larger sand, dirt or rust, protecting the RO membrane in stage 3.
  • In stage 2, a 5-mciron carbon block filter can get rid of chlorine, bad tastes and smells
  • In stage 3, the RO membrane is used to reduce or remove most of the contaminants in the feed water. This is the core stage of a RO system.
  • In stage 4, a carbon post filter is used to polish the filtered water further more. It can remove the strange taste from the RO water. Of course, it doesn’t remove anything. On the contrary, it adds back something to make it taste good.

This RO system comes with everything you need for installation, including the hoses, fittings, a faucet, etc.

Filtration System Design

As a modular RO system, all the parts are well organized and its filters are attached through a manifold. Therefore, all the tubes are kept well and you will get a neater and tidier installation.

The filters fit in their own housing. And the whole system is covered as one. Because of its modular design, it is so easy to replace its filters. Of course, spilled water is inevitable.

First, you need to slightly pull the filter away from the vertical, and then press the button on the manifold, and then you can pull it away. There is a protective cap on the new filter, and you need to remove it first. After that, insert the new filter into the manifold until it clicks. This is the whole process. After that, you need to reset its indicator light by removing and replacing its battery which you can find at the base of the water faucet. After that, you can make your faucet run several minutes. Then it is ready for use.

Water Efficiency

For all RO systems, waste water is inevitable. This is because RO systems need water to flush the RO membrane and create pressure. The amount of water wasted shows how such a RO system takes a use of water. And the water pressure and temperature can influence the result.

This system doesn’t specify how much water it will waste to produce 1 gallon of pure water. For this type of RO systems, about 3 to 4 gallons of waste water will be produced to produce 1 gallon of pure water.

Ease of Installation

It is pretty easy to install it, if there is already a blanked off 1 1/4 inches hole in the sink. Or you may need to drill one. Don’t worry about it. Such a hole in the sink is very common. This hole is used for the installation of the water faucet. Of course, you can use the soap dispenser hole instead.

The manufacturer offers a full installation manual and you can find it at this link.

Pros & Cons


  • Up to 50 gallons of pure water output per day
  • RO filter life: 2 to 5 years
  • Other Filters’ life: 6 months for the stage 1 and 2 filter, 1 year for the stage 4 filter
  • A modular design
  • Has a LED indicator to remind when to change its filters
  • Comes with an air gap faucet
  • A 3-year manufacturer’s limited warranty is included


  • Only comes with a 3-gallon storage tank, smaller than others (4-gallon is very common)
  • Only a 4-stage RO system


Question: Does this RO system remove fluoride from tap water?

Answer: Yes, of course. Therefore, this system removes all the bad taste.

Question: How to change the indicator battery?

Answer: Just find and replace it. It is behind a small rubber wedge below the faucet handle.

Question: Is the water storage tank is BPA-free?

Answer: Yes, of course. Polypropylene is a new material certified by ANSI, FDA, NSF, which is BPA-free.

Question: How often change filters?

Answer: The first 2 stage filters are changed every 6 months. The RO membrane filter can last 2-3 years. And the stage 4 filter is changed every year. Well, the feed water quality and the use may influence their life.

Question: How long to install?

Answer: If you have read its user manual or watch some installation videos, and you have good tools, you can finish it in less than 2 hours, or even within 1 hour.


As a 4-stage under sink reverse osmosis system, its affordability, ease of installation, built-in indicator, modular design and longer filter life make it very competitive. If you just need a basic RO system, this one is definitely one of the best reverse osmosis systems you can trust.

Watts Premier WP531411 4-Stage Reverse Osmosis System Review

Leave a Reply

Your email address will not be published. Required fields are marked *