Written by: Gene Fitzgerald // Last Updated:
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Changing the filters and the membrane of your reverse osmosis system on a regular basis is key if you want great tasting drinking water that is clean and healthy.
And the good news is that it can be done by the average Joe with zero plumbing experience. All you need are some basic supplies and a little bit of patience.
Ready to get started? Time to replace RO filters!
Here is how to replace the filters and membrane of a reverse osmosis system:
We get it, you don’t want to replace your reverse osmosis filters too often and waste money, but you also don’t want to leave them in for too long putting your health at risk. No worries, simply follow this RO filter replacement schedule to be on the save side:
|Biannual Replacement||Annual Replacement||Every 3 to 5 Years|
|Sediment and carbon pre-filters||Sediment and carbon pre-filters|
What’s most important is that you change on a regular basis. It’s the only way to guarantee consistent water quality. How often primarily depends on 2 factors:
That being said, regular sediment and carbon pre-filters should last between 6 and 12 months. A carbon post-filter is usually good for 12 months, although some may last up to 2 years.
Please consider these as general guidelines. Especially cheap aftermarket filters might require more frequent replacements.
By the way, if you are going to buy from another source make sure that the quality is up to standards – think NSF certifications.
Failing to change filter elements in a timely manner will
All four are indicators that a filter replacement is probably overdue.
Sediment pre-filters are found in stage 1, sometimes stage 1 + 2, of almost all RO under sink filter systems on the market. They trap rust, sand, silt and other debris to protect the delicate reverse osmosis membrane at the heart of the system from premature clogging.
Sediment pre-filters in a reverse osmosis system should be replaced every 6-12 months.
Carbon pre-filters are found in stage 2 (and 3). The cartridges contain activated or catalytic carbon in granular or block form. The filters are most effective at removing chemicals including chlorine plus its disinfection byproducts and VOCs which would otherwise damage the RO membrane. They are also great to eliminate tastes and odors.
Carbon pre-filters in a reverse osmosis system should be replaced every 6-12 months.
Carbon post-filters come into play at filter stage 4 or 5 and give your water a finishing touch. They are mainly used to remove residual tastes and odors that might have leached into the water while in the storage tank.
You should change your carbon post-filter every 12 months.
The easiest and safest method to determine if your RO membrane needs changing is by measuring permeate water TDS (Total Dissolved Solids). This can be done with a TDS meter.
First, test the TDS of the untreated tap water. Then test the purified RO water.
You can calculate the TDS rejection rate by using the following formula:
Rejection rate in % = (TDS of untreated tap water – TDS of purified RO water) / TDS of untreated tap water x 100
If the rejection rate drops below 80 percent it is time for a replacement.
Another indicator for a worn-out membrane is reduced water flow from the faucet.
State-of-the-art reverse osmosis membranes usually last for 3 to 5 years, provided that you replace pre-filters according to schedule. If you are on well water and the contamination is particularly bad a new membrane might be required every year or so.
So, how to change reverse osmosis filters?
Although every model is a bit different, here are some basic steps that apply to most RO units:
Before you start, you should check the product manual. It most likely includes detailed instructions that outline the filter replacement procedure for your specific system.
Finally, write down the date of the filter replacement as guidance for the next. Also, if your RO faucet comes with a filter change indicator remember to change the battery.
Eric from emoneyblue has done a great job demonstrating how to replace RO system filters (+ the membrane) in a matter of minutes:
Replacing modular filters is much more convenient. There is no need to turn off the feed water nor to release pressure. Simply place a bowl underneath the system, twist off the old filters and install the new. Don’t forget to check for leaks! That’s all.
Lead, fluoride, bacteria – a reverse osmosis membrane that is in good condition removes up to 99% of all water contaminants.
How to keep a membrane in good shape? First and foremost, through regular cleaning and appropriate pre-treatment of the feed water.
However, even with the most thorough cleaning procedure and the best pre-treatment in place, every RO membrane has to be replaced eventually…
Before you start, you should check the product manual. It most likely includes detailed instructions explaining how to replace the RO membrane on your specific system.
As with the filter replacement, it is helpful to write down today’s date as guidance for when to change the membrane next.
Like purchasing reverse osmosis systems, replacement filters and membranes can be purchased from several sources.
Generally speaking though, you’re better off purchasing the replacement filters directly from the same manufacturer that you purchased the system from. While aftermarket filters can work for systems with standard-sized cartridges, you’re not guaranteed the same level of contaminant removal. Aftermarket filters can often be purchased for less than the cost of the original filters, but again you don’t know exactly what you’re getting unless they’re NSF certified.
As mentioned previously, the best option is usually to purchase directly from the RO system manufacturer. That way you know you’re getting the exact replacement filters you need, and you won’t have any warranty issues should you run into trouble with anything.
Another option is purchasing replacements from a large online retailer. These retailers typically have large product selections, so there’s a good chance you’ll find your brand’s filters available.
If you’re willing to take a gamble with aftermarket replacement filters, then a large online retailer is the way to go. They typically have the cheapest prices, offer discounts, and you’ll be able to return anything if it doesn’t suit your needs.
If you have a local water treatment supplier, they may have what you need available, but keep in mind you’ll likely pay more than you would when purchasing from an online retailer.
Hardware stores may also have replacement filters available, and they generally offer a good blend of price and availability. Returns are also easy should you have any compatibility issues.
Replacement filter costs will vary depending on the filter quality, brand name, and the specific filter element you need.
Generally speaking though, pre and post-filters will run you between $10 on the low end to $50 on the high end. RO membrane replacements cost between $25 on the low end and $100 on the high end.
You can also purchase filter replacement sets that have all of the required pre and post-filters – including the RO membrane – for less than the cost of purchasing each one separately.
If you have any questions about how to replace RO filters please don’t hesitate to leave a comment below!
I calculated my rejection rate to 4% after replacing previous filter, post filter and cta ro membrane. I then completely drained the bladder tank and the rejection increased to 5 %.Reply