Reverse Osmosis Membrane Elements
Written by: Gene Fitzgerald // Last Updated: Oct 6, 2022
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If properly maintained, a reverse osmosis system provides you with clean, healthy and great tasting drinking water.
Furthermore, a unit that’s kept in great shape can last for many years, even more than a decade. Fail to do so, however, and you may end up with contaminated water.
The good news is that the required maintenance is low. Also, regular filter and membrane replacements and system cleaning/sterilizing can be done by the average homeowner without the need to be an expert plumber. Want to learn more? Read on!
How to maintain a reverse osmosis system:
This reverse osmosis maintenance schedule will help you stay on time with the different tasks:Biannual TasksAnnual TasksEvery 3 to 5 YearsReplacing pre-filtersReplacing pre-filtersReplacing post-filter(s)Replacing RO membraneSystem cleaning/sanitizingChecking storage tank pressure
The most important aspect of maintaining your reverse osmosis system is to change the pre and post-filters on a regular basis.
This depends first and foremost on the condition of the feed water and your water consumption. For example: Hardness or high levels of sediment as often found in well water can lower the lifespan of the pre-filter elements significantly. And, of course, the more water you use for drinking and cooking, the sooner your filters will wear out.
As a rule of thumb, pre-filters should be replaced at least every 6 to 12 months. A carbon post-filter can last as long as 2 years. In addition, cheap filters might require more frequent replacements as they tend to wear out quicker. For more information we recommend that you refer to the user manual.
On a side note: It is essential that you get the correct filters for your unit. Almost all manufacturers sell replacement parts including filters, so visit their website first. If you are going to buy from another source double-check that the quality is up to standards.
One thing is for certain, failing to change filters in a timely manner will
Bottom line: Make sure that you stay on schedule and change filters (and the membrane – more info below) in due time.
By the way, all 4 aspects listed above can be taken as clear indicators that filter replacements are overdue. What’s more, you might notice an unpleasant taste and/or odor in your water.
Stage 1 of the vast majority of reverse osmosis water filter systems makes use of a sediment pre-filter. The goal is to protect the delicate RO membrane at the heart of the system from clogging – clogging from dirt, rust, silt and other kinds of debris which get trapped in the filter.
You should replace the sediment pre-filter every 6 to 12 months.
Changing the filters of your old RO system doesn’t make much sense anymore? You might be better off with an entirely new unit – reviews here.
Usually at stage 2 & 3, carbon pre-filters come into play. Activated/catalytic carbon or charcoal is great for removing chemicals from water, first and foremost chlorine and other disinfectants, which would otherwise affect the performance of the reverse osmosis membrane. Thin film composite (TFC) membranes are particularly susceptible to free chlorine.
Block or granular – carbon pre-filters require changing every 6 to 12 months.
Did we mention that a carbon filter also greatly improves water aesthetics?
And lastly, we have a carbon post-filter (filtration stage 4 or 5). It has the purpose to give your water a refining touch right before it comes out of the faucet. The carbon removes any residual tastes and odors that may have leached into the water while being stored in the pressure tank.
Carbon post-filters should be changed about every 12 months. Some may even be good for up to 2 years.
Before you attempt to replace your system’s filters make sure to take a look in the product manual. It likely includes specific step-by-step instructions not only for filter/membrane replacements, but also for other maintenance works.
This will give you a basic idea of the process (keep in mind that every model is a bit different):
What about the RO membrane?
A semipermeable reverse osmosis membrane that is in good condition removes up to 99% of all remaining contaminants from your water. This includes lead, arsenic, fluoride, chromium, 98-99% of waterborne pathogens and much more. TDS drop to almost 0.
RO membranes last longer than the various filters, not seldom up to 3 or 5 years, provided that you replace pre-filters according to schedule. In some applications, a new RO membrane is required every 1 or 2 years.
FYI: The safest way to determine if your membrane needs changing is by using a TDS meter. If the rejection of output water TDS drops below 80% it is time for a replacement.
Again, to find out how you can replace your system’s RO membrane you should consult the manual.
Cleaning and sanitizing a reverse osmosis system is not necessary in all cases. However, the whole process is neither overly complicated nor time consuming, which is why we recommend you follow through with it to be on the safe side.
How often to clean/sanitize? With each filter replacement – ideally once a year, maybe twice if need be.
As always, for specific instructions refer to the owner’s manual. Alternatively, follow this link to learn how to clean and sanitize a reverse osmosis system. In a nutshell:
Meanwhile, you can soak the membrane in different chemical solutions, depending on its type and as recommended by the manufacturer. This helps to eradicate organic matter and remove stuff like mold and mildew – think fouling. It will also prevent scaling. Both are important for optimum operating pressure, water output and water quality.
Adequate storage tank pressure is important for your RO system to function properly. Thus, you should check it about once a year. Any low pressure gauge will work fine for this.
FYI: A tank may lose about 1 psi per year.
What’s important is that you measure the pressure when your tank is empty. It should read somewhere around 6 – 8 psi. In case your tank is underpressurized you can use a simple bicycle pump to fix it.
Want more info on how to drain and repressurize an RO tank?
While most people choose to maintain their reverse osmosis system themselves, you have the option to hire a local water treatment specialist to do the work for you.
After-sales services are provided by a range of companies, so reach out to 2 or 3 and ask for prices for better comparison.
If you have any questions or thoughts about RO maintenance please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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