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Reverse osmosis membranes are designed to block contaminates and provide purified drinking water.
But while they’re built to stay efficient for years, at some point, they start deteriorating.
In some cases, you can spot that something is off with your RO system easily. But even if everything seems normal, it’s important to know how to check if the membrane is still doing its job properly, to maintain water quality.
The RO membrane is the heart of your reverse osmosis water filtration system. If it’s clogged, dirty, or no longer efficient to filtrate, it is important to catch these signs on time to continue drinking clean water.
Here are the best ways to check whether an RO membrane is working in tip-top shape or not.
If you’re looking for the most accurate way, then look no further. Checking whether the membrane is still efficient in rejecting the flow of dissolved substances is crucial, as it gives you the clearest picture of how pure your filtered water is.
To check your RO membrane’s the salt rejection rate, you will need a TDS meter. Don’t worry, these aren’t overpriced gadgets, but they can be of real help when it comes to keeping your water quality high.
The TDS meter can test the conductivity of your filtered and raw water respectively. Meaning, it can check how well the passage of dissolved solids is obstructed by the membrane. Once you have the rejection rates from your filtered and unfiltered water, you can calculate the overall efficiency of the membrane and see if it needs changing.
The formula is simple, and you don’t need to be a math whizz to determine the salt rejection rate.
And there you have it! If your rate is below 80%, that is a sign of concern and a good indicator that it’s time for a new reverse osmosis membrane.
Checking how well the output water flows can also be of great help. The RO membrane works by blocking debris and contaminants from passing through. And over time, especially if the feed water is rich in floating chunks, these impurities can get the membrane clogged.
If you have been dealing with obstructed water flow (and you’re sure you’re not dealing with other issues like pressure, temperature, etc.) then the culprit may be hiding in the RO membrane. In tank-dependent systems, this can cause the tank to take too long to fill.
Sometimes you can spot that there is something off with your filtration system after only a sip. Or a glance. Or even a whiff. That’s right, your senses can also be good inspectors when it comes to the quality of your drinking water.
Fill up a glass of RO water and check the aesthetics. Does it look clean? Or is it murky? Does it have a certain smell? How does it taste? If you notice that something’s wrong with how the water looks/tastes/smells, the membrane might be to blame.
If you have been enjoying the purified perks of an RO system, then you might be used to drinking your water at a certain quality. If the water quality is (even slightly!) lower than what it used to be, that may be a sign that the membrane has started losing its efficiency.
Over time, gunk can pile up on top of the RO membrane, which can result in blocking the flow of the water, redirecting it towards the drain line.
If you have an RO tank, a clogged membrane will never fill it up. That means that, unless the membrane gets replaced, the system will go on a never-ending run, rejecting water, and pushing it down the drain.
A clear sign of concern is if the membrane changes its color as a result of being coated with layers of debris. To check this, you need to open the housing of the RO membrane and see if it’s still white on its sides. If you notice red, yellowish, or brown discoloration, then it is time to replace the membrane.
The manufacturer of the reverse osmosis membrane you’re using has specified the ideal time to have it changed.
Think of this as a “best before” date on a product. Enjoying it past that date may not necessarily make you sick, but it surely won’t provide the same results.
So, if the manufacturer states that it is best to change the membrane after 3 years, it probably really is. The membrane may still be able to prevent some impurities, but it surely won’t be as efficient as before.
There are many reasons why the RO membrane may not be filtering properly. Sometimes, the impure feed water may not be even to blame. Knowing what affects the performance of the membrane is crucial. Getting a new membrane will not always fix the issue.
This is probably the most straightforward issue. The membrane doesn’t pass enough water through, causing a low flow rate, draining, and impaired quality. This happens as a result of either dealing with incredibly impure water or using the same membrane for too long. Layers of debris can block the pores of the membrane, affecting clean water production.
If your RO membrane is past its prime date or blocked by impurities, it is time to replace it. And here is how to do it:
A reverse osmosis filter system cannot function properly if the feed water pressure is low.
The pressure level has to be at least 40 psi for the system to be able to work, but at 60 psi, the results are much better. Generally speaking, you will need a pressure level of 40-85 psi for RO filtration.
If your feedwater pressure is lower than 40 psi, filter system will not be able to push enough water through its membrane. That will cause most of it to flow down the drain wasted.
For low water pressure, your best bet is to install a booster pump. The pump will then push the water through the system at a rate that’s fast enough for it to function properly.
The productivity of the RO membrane is sensitive to changes in the temperature of the feed water. As the water gets warmer, it also gets thinner, and more water permeates the membrane. As it gets colder, the water gets thicker, and so the flow rate of filtered water decreases.
The normal working temperature of RO membranes is 77 °F (or 25 °C), but anywhere from 40-100 °F (5-35 °C) will work.
At a higher temperature, the water has a higher diffusion rate and lower viscosity. This helps it pass through the membrane pores.
If you find that your water flow rate is affected by cold water temperature in winter, you might want to try boosting the water pressure a bit to improve it.
Another thing that can prevent a reverse osmosis membrane from working properly is if your feed water has an abnormal pH. Of course, this is incredibly rare as most water supplies have a pH that is within the recommended range, still, it is good to know that your water’s pH should be at least 2.0 and no more than 11.0.
The same goes for the TDS level in the water. The more dissolved solids, the harder the membrane works to let water through the pores and leave these impurities behind.
Maybe your RO membrane isn’t the problem at all. Perhaps the RO system doesn’t seem to be working because of a pre or post-filter issue. Check your filter additions and see if they’re functioning properly.
Depending on the manufacturer, your feed water, as well as how often you utilize the filtered water, you can expect your RO membrane to be providing you with purified water for 2 to 5 years.
If you have any questions about how to check if an RO membrane is working or not please don’t hesitate to leave a comment below!
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