Large selection of replacement water filters, reverse osmosis membranes, testing kits and water filter system repair parts. From one water filter or membrane to case quantity discounts.


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Aquaflex Water Filters ®

AquaFlex ® PRO-4 Tank is the tank number for a standard tank that is used on many, many reverse osmosis systems. Identifying the tank will not identify the RO system or replacement filters. Most systems using this Aquaflex Saniflex tank used standard size replacement filters and reverse osmosis membranes. For help matching up your system see:

Help Identifying Systems Using Aquaflex Tanks. Choose from pictures.

While the tanks in the help file may look different from the AquaFlex PRO-4, look to match the described configuration of the filters. The systems shown are using other generic tanks in place of the AquaFlex PRO-4.

Easy TDS Membrane Performance Calculator
See If It is Time To Replace Your Membrane

Simply enter your Feed Water TDS and RO Water TDS into the boxes above and click "Submit". The percentage of TDS Rejection will be displayed. We normally recommend membrane replacement once you drop below 75%. This may vary in areas with high TDS in the feed water.

See our selection of TDS meters under Water Tests

Be sure to check our Parts Department for important parts such as TDS Testers For Reverse Osmosis Membranes, Replacement Tanks, O-rings , Filter Housing Wrenches, Faucets, Pumps, Fittings, UV Systems and more parts for your reverse osmosis pure water filtration system.   View maintenance and servicing tips online at our Installation & Trouble shooting Guide.


* AquaFlex ® is the registered trademark of AquaFlex, the manufacturer of AquaFlex ® brand water treatment equipment.  The replacement filters and membranes listed above are not manufactured or endorsed by AquaFlex.  Rather, these filters and membranes are manufactured by other companies.  While these filters and membranes are compatible for use in AquaFlex ® brand water treatment equipment, we make no representation as to whether using these filters and membranes is consistent with the warranty and specifications applicable to AquaFlex ® Saniflex equipment.