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.

LOW PRICES and FAST SHIPPING ONLINE SINCE 1999 !

99.5% Of All Items In Stock For Same Day Shipping!

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.





* Vertex is the registered trademark of Vertex, the manufacturer of Vertex brand of under counter drinking water system filtration equipment.  The replacement water filter cartridges, reverse osmosis membranes, water tanks, faucets and repair parts listed above are not manufactured or endorsed by Vertex.  Rather, these replacement filters, RO reverse osmosis membranes and replacement parts are manufactured by other companies.  While these replacement water filters, repair parts and reverse osmosis membranes are compatible for use in Vertex under counter reverse osmosis drinking water filtration equipment, we make no representation as to whether using these water filter cartridges, replacement parts and RO reverse osmosis membranes is consistent with the warranty and specifications applicable to Vertex under sink drinking water system equipment.