What Is the Average Lifespan of an RO Membrane?
Written by: Alexandra Uta // Last Updated: Mar 21, 2023
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Knowing your RO membrane’s lifespan is vital if you want to keep your reverse osmosis system in good shape.
This article details the average life of RO membranes and the various factors affecting it.
Let’s go!
Contents
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Key Takeaways
- The average lifespan of an RO membrane is 2 to 5 years, depending on factors like feed water hardness or TDS levels, RO membrane type, level of overall impurities, chlorine concentrations, the volume of water used, and maintenance practices.
The Lifespan of an RO Membrane
The average lifespan of an RO membrane is 2 to 5 years, depending on certain factors as discussed below.
Factors That Influence RO Membrane Life
- Water hardness/TDS levels: Hard water forms scale on a reverse osmosis membrane. These scale deposits clog the membrane and reduce its efficiency and lifespan significantly. The same goes for dissolved solids in general. Higher TDS means the membrane has to work harder, leading to a shorter lifespan.
- Membrane type: Membrane life is also dependent on the type of membrane. Generally speaking, thin film composite (TFC) membranes last longer than cellulose triacetate (CTA) membranes. And while TFC membranes are also more effective (with a higher salt rejection rate than CTA), they are more susceptible to chlorine damage.
- Level of impurities: This can disrupt the life of the RO membrane. The more impurities present in the feed water aside from TDS, the shorter the life you can expect from your reverse osmosis membrane since it would need to work harder.
- Chlorine level: As mentioned, TFC membranes are highly sensitive to chlorine, and it significantly reduces their lifespan. Your RO membrane will go bad much faster if your water contains high chlorine levels that aren’t removed prior to the reverse osmosis process. This is why RO systems use carbon pre-filters to remove chlorine before sending the water to the membrane.
- The volume of water used: Naturally, the more water you use and treat, the sooner you’d need to change your RO membrane.
- Membrane’s time in service: The older the membrane and the longer it has been used, the sooner you’d need a replacement. RO membranes last two or a few more years with proper maintenance. If the membrane has been working for longer than two years, you should know it’s nearing the end of its life.
- Maintenance practices: A well-maintained RO membrane will last longer than a poorly maintained one. To properly maintain your RO membrane, replace pre-filters on time to prevent sediment and chlorine from reaching it. Also clean your RO system once or twice a year.
- Membrane flushing and cleaning: Flushing and chemical membrane cleaning can also prolong membrane lifespan, but not many people do it.
Reverse Osmosis Membrane Shelf Life
Most reverse osmosis membranes are manufactured and shipped in dry. They have an indefinite shelf life as long as you store them properly and keep them dry.
RO membranes are best stored in a cool, dry place away from direct sunlight. The storage limits are 40-95°F (5-35°C).
Maintenance Schedule: How Often to Replace Your RO Membrane
Again, several factors affect an RO membranes’ lifespan. And some membranes will last longer than others, based on the water quality and how they’re maintained.
But generally, you should replace an RO membrane every 2 to 5 years. Most manufacturers provide specific instructions on how often to replace.
How to Know When Your RO Membrane Is Bad and Requires Changing
There are tell-tale signs to look out for that tell you when your RO membrane needs to be replaced. Let’s get into some of them:
Poor Water Quality
A common warning that your RO membrane is bad and needs changing is a drop in output water quality. If you notice a general decline in your water’s quality in terms of color, odor, and taste, then something is wrong. These sudden changes in your water quality are often caused by sediments or scale clogging up the RO membrane, which means it’s time to replace it.
Decrease in Output Water Flow
Another sign you need to change your RO membrane is a drop in output water flow. Water flow typically drops when the membrane has fouled. So if you notice a drop in flow, it’s probably time to get a new membrane.
RO System Runs Continuously
If your RO system runs continuously, that could be a sign of a clogged membrane, too. It runs continuously because the storage tank does not fill properly. When this happens, it’s time to change the membrane.
High TDS Levels in RO Water
An increase in filtered water TDS definitely indicates that your RO membrane is no longer working as it should. Thus, routinely measuring the TDS level in your RO water can help you stay aware of your membrane’s current state.
Manufacturer Says So
Manufacturers usually recommend dates for changing filters and RO membranes. So the system manual is an excellent place to start if you need help determining when to change your RO membrane.
When to Change Sediment Pre-Filters
Sediment pre-filters are present in all reverse osmosis systems. They trap sediments and other debris and protect the RO membrane from getting clogged too soon. Sediment pre-filters should be changed every 6-12 months.
When to Change Carbon Pre-Filters
Carbon pre-filters are in stage 2 (and sometimes 3) of an RO system. They remove chemicals like chlorine and its disinfection byproducts. They also remove VOCs all of which can cause damage to an RO membrane.
Carbon pre-filters should be replaced every 6-12 months.
When to Change the Carbon Post-Filter
Carbon post-filters are found at stage 4 or 5 of the RO system. They give the water a final polishing touch. They should be changed every 12 months.
How to Measure the Performance of Your RO Membrane
The best way to ascertain the performance of your RO membrane is by measuring the total dissolved solids (TDS) levels in the permeate water using a TDS meter.
To do this, test the TDS of the raw water, then test the filtered RO water.
This formula gives you the TDS rejection rate:
Rejection rate in % = (TDS of raw water – TDS of RO water) / TDS of raw water x 100
If the rejection rate is lower than 80%, your RO membrane isn’t performing well, and it’s time to change it.
Further Reading:
How Long Does a Reverse Osmosis System Last?
A reverse osmosis system will last 10 to 15 years with proper maintenance (and changing of parts when due).
If you have any questions about reverse osmosis membrane life please don’t hesitate to leave a comment below!
About the Author Alexandra Uta
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