Many times, the membrane type and capacity are written on the membrane housing itself. 

Type of Membrane
Membranes come in two types, CTA (Cellulose Tri-Acetate) and TFC (Thin Film Composite) sometimes labeled as TFM (Thin Film Membrane). CTA Membranes can tolerate chlorine and TFC Membranes cannot tolerate chlorine. TFC Membranes are more efficient and are the standard type used in today's RO Systems, although systems using CTA membranes are still being manufactured. 

CTA membranes are usually have a capacity of 16 GPD (Gallons Per Day) or less.

TFC (TFM) membranes for residential use are now available at up to 150 GPD.

If your system does not have a label which tells you which type membrane you have, you may have to remove the membrane and look on the label.

Membrane Capacity
Most RO Systems list, on the membrane housing, the capacity of the membrane in GPD (Gallons Per Day). Of course, this makes it easy to find the replacement but if you're reading this, your system most likely does not tell you the capacity. 

Why is this important? To operate efficiently, RO Membranes are matched to the proper size Drain Flow Restrictor. The RO Membrane and Drain Flow Restrictor must be matched to keep the proper balance between waste water and pure water. Mismatching can either cause excessive waste to the drain or premature membrane fouling. 

There are two ways to determine the membrane capacity of your system. One is to remove the membrane and look at the label. The label should tell you the membrane Type and Capacity.

The other is to look at the membrane Drain Flow Restrictor. Most standard RO Systems use an inline Drain Flow Restrictor like the one pictured here. Although not shown in this picture, the Drain Flow Restrictor has a number on it such as 150, 200, 250, etc.

As the Drain Flow Restrictor is sized to the Membrane Capacity, all you need to do is match this number to the chart and you will know the capacity of the membrane your system is currently using.
 

Number On Flow Restrictor	Membrane Capacity
150	16-18 GPD
250	24 GPD
350	36 GPD
500	50 GPD
750	75 GPD
1000	100 GPD
1200	150 GPD

How Do I Upgrade To A Higher Capacity Membrane?

This is the easy part. As we mentioned, the RO Membrane and Drain Flow Restrictor are matched. To upgrade to a higher capacity membrane, all you need to do is make sure you also replace the Drain Flow Restrictor to match the new membrane. 

Sizing The Inline Polishing Filter and Tubing

Inline Polishing Filters are available in two configurations. One is with Female Pipe Thread (FPT) and the other is Quick Connect Fittings. 

In this picture, the filter on the Left has FPT fittings (The Blue Cap is a plug to keep debris out of the filter). With this type of filter, you have a fitting that screws into this filter and the tubing connects to this fitting.
 
 
 

The filter on the Right has Quick Connect fittings. With this type, the tubing is simply "Pushed In" to the filter and is held in place by the Quick Connect Collar.
 
 
 
 
 
 
 
 

If your inline polishing filter has FPT threaded fittings, the most common size is 1/4". 

As you can see in this picture, 1/4" FPT is approximately 1/2" wide if measured with a tape measure.
 
 
 
 
 
 
 
 

Tubing Size

The tubing on the LEFT is 1/4" tubing. The tubing on the RIGHT is 3/8" tubing. Most times, the tubing is labeled with the size. Just look on the tubing and it will have writing on it telling you the type and size.
 
 
 
 
 
 
 
 
 

Holding Tank Air Pressure Gauge
 

The number one reason for low water flow from a reverse osmosis system is low air pressure in the holding tank. With this holding tank air pressure gauge you can easily check and maintain the holding tank air pressure to the required 8 PSI of air pressure to get your system up and running at its' peak efficiency. Specially designed for use with low air pressure applications, this Holding Tank Air Pressure Gauge is a must for Reverse Osmosis Systems maintenance.  Quantity: $9.95

TDS Meter
 

HM Digital, Inc., TDS-EZ Total Dissolved Solids Meter The HM Digital EZ TDS meter is a must for reverse osmosis (RO) filter and membrane monitoring. Know when to change your pre-RO filters to extend the life of the RO membrane. Designed for home use, this pocket TDS meter comes with a 2 year limited manufacturer's warranty.Designed for the long haul, this compact TDS (Total Dissolved Solids) meter has been manufactured with a tough housing and large, easy to read LCD screen. It sports a measurment range of 0 to 9990 parts-per-million. Flip it over and the back side sports a handy color coded chart which classifies the water you are testing.The TDS-EZ is perfect for monitoring your reverse osmosis (RO) output water. Take the guess-work out of knowing when to change your filters!  Quantity: $22.45

 

*The replacement filters and membranes advertised on this site are not manufactured by the companies that manufacture the underlying water treatment equipment unless so noted.  Our use of registered trademarks, such as Culligan®, Kiss®, Premier Manufactured Systems® and others, is only for purposes of identifying compatible replacement filters and membranes, and does not suggest any association, sponsorship or endorsement of our our products by the manufacturers of the underlying equipment. "COMPATIBLE" Legal Disclaimer COPYRIGHT Purewater4u.com is a trademark of Purewater 4U of Las Vegas, Inc. All other products mentioned are registered trademarks or trademarks of their respective companies. Proprietary contents contained herein are the sole property of Purewater4u.com and Purewater 4U of Las Vegas, Inc. and may not be reprinted, reproduced or transmitted in any form without written permission. Purewater 4U of Las Vegas, Inc., grants permission to electronically copy and to print hard copy portions of this site for the sole purpose of placing an order with or through Purewater4u.com, or using this site as a shopping resource. Any other use of materials on this site, including reproduction for purposes other than those noted above, modification, distribution, or republication, without prior written permission from Purewater 4U of Las Vegas, Inc. is strictly prohibited. Copyright © 1998 - 2011 Purewater 4U of Las Vegas, Inc. Las Vegas, NV, USA. All rights reserved.