Learn About Reverse Osmosis

Certified RO systems

At NZ Pump and Water Filters, we specialize in Reverse Osmosis technology, and we are proudly based in New Zealand. 

Is certification important?

Yes, certification is an important factor when considering an RO system.

NSF/ANSI Standard 58, titled "Reverse Osmosis Drinking Water Treatment Systems," is a set of guidelines and requirements developed to ensure the safety and performance of reverse osmosis (RO) water treatment systems. These standards are established by NSF International, an independent organization that tests and certifies products to protect and improve human health. The American National Standards Institute (ANSI) accredits these standards.

What can RO water be used for?

  1. Cooking: RO water can enhance the taste of cooked food, especially sensitive dishes like soups, broths, and sauces, by removing impurities and contaminants.

  2. Ice Making: Using RO water in ice cubes can result in clearer and better-tasting ice due to the removal of minerals and other impurities.

  3. Beverage Preparation: Whether it's coffee, tea, or any other beverage, using RO water can improve the taste and quality by ensuring it's free from contaminants.

  4. Household Cleaning: RO water can be used for cleaning purposes, such as filling steam irons, humidifiers, or mixing with cleaning solutions for better results.

  5. Appliance Maintenance: Using RO water in appliances like steamers, humidifiers, and even in household appliances like irons and coffee makers can prolong their lifespan by preventing mineral buildup.

  6. Plant Watering: Some plants are sensitive to minerals and impurities in water. Using RO water for watering plants can prevent mineral buildup in the soil, helping them thrive.

  7. Aquariums: RO water is often used in aquariums to provide a clean and safe environment for fish and aquatic plants, as it lacks the impurities found in tap water that can harm aquatic life.

  8. Medical Applications: In medical settings, RO water is used in various procedures, such as laboratory testing, medical equipment sterilization, and dialysis, where the purity of water is crucial.

  9. Cosmetic and Personal Care: RO water is often used in cosmetic formulations and personal care products to ensure purity and prevent contamination.

  10. Battery Maintenance: In industries where batteries are used, RO water is often employed for topping up lead-acid batteries to prevent mineral contamination, which can affect battery performance.

  11. Colloidal silverUsing RO water for making colloidal silver can be beneficial because it provides a clean and pure water source free from impurities and contaminants.

Is RO water safe for drinking?

Reverse osmosis (RO) water is generally considered safe for drinking and is widely used for its ability to remove a broad spectrum of contaminants from water. 

However, it's essential to consider a few factors:

  1. Mineral Content: One potential drawback of RO water is that it can remove beneficial minerals along with contaminants. While some minerals are essential for health, they are typically obtained from the diet rather than drinking water. If you rely on RO water as your primary source of drinking water, you will want to ensure you're getting essential minerals through remineralizing the water such as the Oasis DP RO


Our quality Oasis DP RO comes complete with a remineralizing filter as the last and final 6th stage. Here are the benefits:

  1. Mineral Content: RO systems remove minerals along with contaminants during the purification process. While some minerals are essential for health, they are primarily obtained from food rather than drinking water. If you have concerns about mineral intake or prefer water with a slightly higher mineral content for taste reasons, a remineralizer can be beneficial.

  2. pH Balance: RO water tends to be slightly acidic due to the removal of alkaline minerals. If you prefer water with a balanced pH or have concerns about the acidity of RO water, a remineralizer can help adjust the pH and improve taste.

  3. Health Considerations: If you rely heavily on RO water as your primary drinking water source, especially if you consume large quantities daily, you may want to ensure you're getting essential minerals. Remineralizing the water can help replenish some of these minerals.

  4. Taste Preferences: Some people find that remineralized water tastes better than pure RO water, which can sometimes taste flat or lacking in flavor due to the absence of minerals.

Choosing the best option for your application

Choosing the right RO (Reverse Osmosis) system for your needs involves considering several factors to ensure you select a system that meets your water quality requirements, budget, and installation preferences. Here's a step-by-step guide to help you choose an RO system:

  1. Water Quality Testing: Begin by understanding the quality of your tap water. You can do this by either using a home water testing kit or by obtaining a water quality report from your local water utility. This will help you identify the specific contaminants present in your water and determine the type of filtration needed.

  2. Contaminant Removal: Based on your water quality test results, identify the contaminants you want to remove or reduce with an RO system. Look for RO systems that are certified to effectively remove those contaminants. Common certifications to look for include NSF/ANSI Standard 58 for RO systems.

  3. System Capacity: Consider the daily water usage in your household or business to determine the capacity of the RO system you need. RO systems are available in various capacities, ranging from small under-sink units to larger whole-house systems. Choose a system that can meet your daily water demand without overburdening the system.

  4. Efficiency and Wastewater Ratio: Pay attention to the efficiency of the RO system and its wastewater to purified water ratio. Look for systems with higher efficiency ratings and lower wastewater ratios to minimize water wastage.

  5. Ease of Installation: Determine whether you prefer a DIY installation or if you'd prefer to hire a professional. Some RO systems are designed for easy installation with detailed instructions, while others may require professional installation.

  6. Budget: Set a budget for your RO system purchase, taking into account not only the initial cost of the system but also ongoing maintenance expenses such as filter replacements. Consider the long-term cost-effectiveness of the system, including its energy efficiency and lifespan.

  7. Additional Features: Consider any additional features or options you may want, such as remineralization cartridges. These features can enhance the performance or convenience of the RO system but may come at an additional cost.

  8. Brand Reputation and Warranty: Research the reputation of different RO system brands and manufacturers. Look for reviews and customer feedback to gauge reliability and customer satisfaction. Additionally, check the warranty coverage offered by the manufacturer to ensure adequate protection against defects or malfunctions. 

On the other hand, if you are primarily concerned with removing contaminants and prefer the purest water possible, you may opt to forgo a remineralizer and continue drinking pure RO water.

Ultimately, the decision to use a remineralizer with your RO system is a personal one based on your preferences and individual circumstances. If you're unsure, you could try both options and see which one you prefer in terms of taste and overall satisfaction.

What does an RO water purifier do?

Reverse osmosis is a water purification process that uses a semi-permeable membrane to filter out unwanted particles and contaminants, resulting in clean drinking water. In this process, applied pressure is used to overcome the natural osmotic pressure, pushing water from high concentrations of contaminants to low concentrations, forcing contaminated water through the filter, and leaving only pure water behind.

The stages of filtration include a sediment filter, pre-carbon block, reverse osmosis membrane, and post-carbon filter. The sediment filter removes the largest particles, the pre-carbon block prevents larger particles from passing through and prevents chemical compounds from passing to the next filter, the reverse osmosis membrane removes molecules heavier than water, and the post-carbon filter polishes the water.

Rigorous testing has shown reverse osmosis water filters to effectively remove arsenic, lead, fluoride, and more. And while there are other purification options out there, many experts consider reverse osmosis to be one of the most thorough, effectively removing up to 99% of these contaminants. So if you're on the hunt for some peace of mind when it comes to quenching your thirst, consider investing in a reverse osmosis water filter.

Reverse osmosis water filtration systems offer a remarkable solution by effectively removing up to 98% of total dissolved solids (TDS) from water, ensuring your home has access to the purest water possible. These filters are highly proficient at eliminating a wide spectrum of contaminants from your drinking water, including chlorine, fluoride, cryptosporidium, and hexavalent chromium.

When it comes to improving the taste and safety of your water supply, a reverse osmosis filter stands out as the most effective solution for eliminating impurities that can negatively impact both flavor and water quality. Installation is a straightforward process that typically requires the assistance of a plumber. If you're considering an under-sink or under-bench water filter system, don't hesitate to contact us at NZ Pump and Water Filters. We can discuss the space requirements and tailor a system to your needs.

How long does it take to fill the tank?

Note An RO tank will never be full. If you have a 12 litre tank for example you will have 1/3 of that in purified stored water.

The time it takes for an RO (Reverse Osmosis) storage tank to fill up depends on several factors, including the size of the tank, the water pressure, and the flow rate of the RO system. However, I can provide a general estimate.

A standard household RO system with a 15 litre storage tank and average water pressure (around 40-60 psi) can take approximately 2 to 4 hours to fill completely after a fresh installation or if the tank has been completely emptied.

The flow rate of the RO system also plays a role in determining how quickly the tank fills up. Higher flow rate systems can fill the tank faster than lower flow rate systems. Additionally, factors such as the temperature of the water and any pre-filters or additional treatment stages in the RO system can affect the filling time.

It's important to note that once the tank is initially filled, it will continuously refill and maintain its water level as long as there is water in the system and the faucet is not in use. The exact time it takes for the tank to refill after each use will depend on the demand for water in your household or business and the capacity of the RO system to produce purified water.

Certified Quality Brands 

NSF/ANSI Standard 58 certified

  • Atlas Filtri  Italian water technology company since 1975
  • Pentair  American water filter companies since 1966 
  • Ecosoft Germany & Belgium water specialists founded in 1998


Do RO systems waste water?

To ensure a Reverse Osmosis system delivers purified drinking water, it must eliminate impurities as an integral part of its operation. The volume of wastewater generated varies depending on the quality of the RO system, and we are proud to offer a range of quality-certified systems.

One perspective on the wastewater is to view it as part of the purification process rather than as water wastage. For instance, when our hands are soiled, we wash them to remove impurities, a standard practice that isn't considered water wastage. Similarly, if the discarded RO water can be collected, it becomes a valuable resource for tasks such as mopping floors, watering the garden, and more. This approach transforms what might seem like waste into a useful resource.

Waste water is often referred to as "brine" or "rejected water"

RO or Standard Carbon filter?

When it comes to filtration options for your home's drinking water, the clear winner is reverse osmosis. While a carbon filter can remove some contaminants, reverse osmosis does a much more thorough job of removing substances like lead, fluoride, and arsenic. In areas with high levels of total dissolved solids (TDS) like minerals and salts, reverse osmosis also shines in comparison to a carbon filter.

Which Filter Removes The Most Contaminants?

When it comes to filtering your water, reverse osmosis water filter systems are top-of-the-line in terms of removing contaminants. In fact, they can remove up to 99% of particles, including lead, arsenic, chlorine, and more. Plus, they also have the bonus effect of reducing excess sodium in the water. For those looking for the ultimate peace of mind about their drinking water quality, reverse osmosis is the way to go. And with NZ Pump & Water Filters' various multi-stage options available, you can tailor your system to meet your specific needs." 

Does the Reverse Osmosis system require power?

Only if you have low pressure in your home and you require a booster pump to increase the systems pressure. Otherwise all of our other RO water Purifiers do not require electrical power.


Will I need a Plumber to Change the Filters?

The Hydronix 4-stage Reverse Osmosis System offered by NZ Pump and Water Filters simplifies the process of replacing water filter cartridges through its user-friendly twist-lock mechanism. You can easily unlock the filter by giving it a simple turn, and the same applies when installing the new filters.

In contrast, the Oasis and EcoSoft Reverse Osmosis systems, also available from NZ Pumps and Water Filters, involve a slightly more involved process. To replace the filter, you'll need to disconnect the tubing, remove the existing filter, and detach the push-fit connections from both ends before attaching them to the new replacement filter. Then, securely place the filter onto the clips and reconnect the tubing. While this may sound complex, it is actually quite manageable and straightforward.

Flush it out

If the RO system has been unused up to 7-14 days it is best that the system is completely flushed out. Completely empty the storage tank.

Cleaning your RO

  1. Maintenance: It's crucial to properly maintain your RO system by  replacing filters when the pressure drops by 1 bar and  also sanitising the system to prevent bacterial growth and ensure optimal performance. Neglecting maintenance can compromise the quality of the water produced.

it is very important to clean the system with a sanitiser with an unscented bleach at least every 12 months


  1. Shut off the cold water supply line leading to the RO system.

  2. If your system is connected to your refrigerator or icemaker, turn off the water line that connects to the icemaker.

  3. Open the faucet of the RO water system and allow all water to drain from the system and storage tank.

  4. After emptying the system, make sure to close the RO faucet handle.

  5. Unscrew the pre-filter housing, typically the filter closest to the feed water line. If you plan to replace the pre-filter, remove and discard it. Keep the filter housing off.

  6. Remove all remaining filters and the reverse osmosis element (membrane). If your RO filter system includes an inline post-filter, retain the old filter unless you are installing a new one. Discard any old filters when replacing them. Refer to the filter manufacturer's instructions for installation and removal guidance.

  7. Reattach all empty housings to the system, excluding the pre-filter housing. There should be no filters in any housings at this stage.

  8. Add two or three tablespoons of unscented bleach (5.5%) to the pre-filter housing.

  9. Reattach the pre-filter housing to the system, now containing the sanitizer solution.

  10. Turn on the cold water supply line to allow the system to fill with the sanitizing solution.

  11. Check for any potential leaks.

  12. Allow the system to fill with water, which may vary in time depending on water pressure. However, it should be full within 5-10 minutes without filters or a membrane installed.

  13. Turn on the RO faucet until water begins to flow out, and then turn off the faucet.

  14.  let the system sit for at least 30 minutes.

  15. After the specified time, flush the system by turning on the RO faucet and letting water run through the system for 5 minutes or until the bleach odor is gone.

  16. Turn off the cold water supply line. Turn on the RO faucet to drain the system completely. Repeat this step twice.

  17. After draining the system completely the second time, either replace or reinstall all filters and the membrane.

  18. Turn on the cold water supply line and inspect for leaks.

  19. Allow the system several hours for the RO membrane to refill the storage tank.