20 Things You Need To Know Before Buying A Reverse Osmosis System!

Reverse osmosis systems have been purifying our water for more than 50 years, so it’s no surprise you might be considering purchasing one However, it’s important to know what reverse osmosis (RO) can and can’t remove, how much a system will cost, and whether it will change the way your water tastes?

Here is everything you need to know about RO’s before you invest in one:

1. Not all RO’s remove pesticides and herbicides

The semi-permeable membrane in a reverse osmosis system is capable of removing pesticides and herbicides from water. However, not all RO semi-permeable membranes are created equal.

According to the Environmental Protection Agency (EPA), laboratory analysis of different reverse osmosis systems found

“…some systems could remove >99% of pesticides and herbicides, while some removed just 23%!!

So, what’s the difference between the systems?

Well, reverse osmosis systems that have a semi-permeable membrane made of thin film composite (TFC) are able to remove pesticides and herbicides.

Unfortunately, when you go to buy a reverse osmosis system the membranes are not always called ‘thin film composite’ on the packaging. So you can’t always tell which one to buy!

The following 3 types of membrane are made from ‘thin film composite’ and can be identified in the product information when you are buying your system.

  • NS-100 (cross-linked polyethylenimine membrane),
  • FT-30 (cross-linked polyamide that contains carboxylate group),
  • DSI (modified polyalkene on a polysulfone base with non-woven polyester backing)

It’s also important to know which reverse osmosis systems don’t remove pesticides and herbicides effectively.

Any reverse osmosis system that has a semi-permeable membrane made from cellulose acetate (CA) or polyamide CANNOT remove pesticides and herbicides.

Be careful though, there is a bunch of misinformation online – there are plenty of websites that state reverse osmosis systems can’t remove pesticides and herbicides because they are made of molecules too small to filter out. This is NOT true!

You just have to make sure the membrane is made of thin film composite!

So knowing this before you buy a reverse osmosis system can help you decide which one you should buy.

2. Removes calcium and magnesium

All reverse osmosis systems are able to remove calcium and magnesium from water. But, why is that important?

When there is a high concentration of calcium or magnesium in water it’s called ‘hard water’ – and most of the U.S. has ‘hard’ or ‘very hard’ water.

Ok, so the good news is that hard water is not bad for us. In fact, calcium and magnesium are essential nutrients for our health.

Unfortunately, calcium and magnesium can be bad news for our reverse osmosis systems.

This means that as your system removes the calcium and magnesium it then builds up on the semi-permeable membrane, essentially clogging it up.

So, if you live somewhere with hard water (basically anywhere in the U.S!!) you will probably have to replace your membrane more frequently than is recommended by the manufacturer.

For health reasons, many people who use reverse osmosis systems choose to add minerals back into their water with mineral drops. Trace Mineral Drops are by far one of the most popular choices. You really only need a couple of drops for a large amount of water, and you can conveniently buy them on Amazon 8oz bottles here.

3. Removes fluoride

Just like calcium and magnesium, fluoride ions are removed when water flows through the semi-permeable membrane.

Fluoride is deliberately added to our water to reduce our cavities and tooth decay – and unfortunately there is no way for us to add fluoride back into our water!!

So, if you have a reverse osmosis system make sure your toothpaste has fluoride in it – otherwise you could end up with some expensive dentist bills!

If you want to know more about the benefits of fluoride and why it’s added to our drinking water you can read about it here in a post I wrote.

4. High water wastage

One of the downsides of reverse osmosis is the amount of water that it wastes.

In fact, according to the EPA reverse osmosis typically wastes 3 times the amount of water that it treats.

This is because of the low water pressure in household pipes

Thankfully, there is a solution – a Booster pump!

A reverse osmosis booster pump will increase the water pressure, which in turn will increase the efficiency of your reverse osmosis system and the flow rate of your treated water.

Don’t get me wrong, your reverse osmosis will work just fine without one – but if you want to reduce the amount of waste water your system makes, then a booster pump is for you.

5. Needs a pressure gauge

Low water pressure is the main cause of reverse osmosis waste water, low water quality, and it also causes low water flows at your faucet. 40 psi or greater is required for a reverse osmosis system to work effectively, and the optimal working pressure should be between 60 and 80 psi.

High water pressure can also be a problem? High water pressure seriously damages the semi-permeable membrane in a reverse osmosis system and can even crack it!

Basically, every reverse osmosis has an optimal operating pressure range for feed water. BUT, every system has a different range – which makes it confusing!

Since it’s really important to monitor the water pressure regularly you would think all reverse osmosis systems would come with a pressure gauge – but surprisingly they don’t.

If the reverse osmosis system that you want to buy is one of the many that don’t, you may want to consider buying a pressure gauge.

I’d recommend this water pressure gauge on Amazon (link to Amazon). They are super easy to install yourself – you just install it along the feed line between the carbon filter and the membrane. Alternatively, just make sure to invest in a system that comes with a gauge at the outset.

6. Removes copper and lead

Reverse osmosis systems remove metals including copper and lead.

The EPA says that the main source of copper and lead in our drinking water is from…

“… Corrosion of household plumbing systems and erosion of natural deposits”.

U.S. Environmental protection agency

Which is seriously concerning!

Water treatment plants do a great job of removing naturally occurring copper and lead from our water during the treatment process. However, these metals are easily picked up from the pipes in our homes and can leach into your drinking water.

The EPA sets the action level for copper in drinking water at 1.3 mg/L. Copper can also cause aesthetic color issues and the EPA sets the for In addition, the secondary maximum contaminant levels (SMCL) for color in water relating to copper

EPA’s National Secondary Drinking Water Regulations (NSDWR) advises water color levels should not exceed the secondary maximum contaminant levels (SMCL).concentraionCopper levels in tap water have an action level of 1.3 mg/L

Sometimes you can tell if there’s copper in your water. Water can taste metallic and cause greenish blue staining in sinks, bathtubs and toilets.

However, copper doesn’t smell and it won’t change the color of the water itself, so it can also be easily missed.

7. Removes chlorine

Ever notice how sometimes your water smells and tastes like chemicals?

Well, more often than not it’s because of chlorine in your water. Water treatment plants use chlorine to disinfect our drinking water.

But some of that chlorine can stay in the water and then it can taste and smell bad.

Luckily, most reverse osmosis systems are effective at removing chlorine.

Unlike some other contaminants it isn’t the semi-permeable membrane that removes chlorine.

It is the carbon filter!

Most systems use Activated Carbon, which is great at removing chlorine!

If you aren’t sure if the reverse osmosis system you are looking at buying has the right carbon filter to remove chlorine, then just make sure that the filter has National Sanitation Foundation certification 42 (NSF-42).

Also, remember it’s extra important to keep your filter clean and well maintained – because if your filter is dirty or out of date then it’s just for show, and the chlorine will pass straight through and end up in your glass of water.

If you want to learn more about chlorine in our drinking water and how it is removed, you can check out a post I wrote here.

8. Removes amoeba

As much as we don’t want to think about it, there are always nasty things around that are too small for the naked eye to see.

Amoeba are one of those things – and are so nasty they can actually be fatal!

Even worse, amoeba are often found in tap water.

Fortunately, the semi-permeable membrane of a reverse osmosis system is able to filter out amoeba.

But be careful, the reverse osmosis system must carry NSF-53 or NSF-58 certification and/or have an “absolute” pore size of 1 micron or smaller to remove amoeba.

Most of the time reverse osmosis systems will have the NSF-58 certification.

If you want to find out more about amoeba in our drinking water and how to remove them check out this detailed post.

9. Removes parasites

There are some seriously nasty parasites that can live in our drinking water. Cryptosporidium and Giardia are two of the most common and nastiest!

Fortunately, reverse osmosis systems can remove parasites from water.

But remember – a reverse osmosis system is only able to remove parasites as long as the filter cartridges and semi-permeable membrane are cleaned and replaced regularly.

To prevent contact with any of the removed parasites the CDC actually advises…

“Anyone changing the cartridges should wear gloves and wash hands afterwards”.

centers for disease control

10. Remove cyanotoxins

It would be fair to say that most people have never even heard of cyanotoxins, let alone know that they can be in our drinking water.

Cyanotoxins are toxins made by blue-green algae (cyanobacteria) and according to an article in the Journal of Environmental Health Perspective the effects of the toxins range from liver damage to neurotoxicity!(Ref 1)

Our community water systems do a great job of getting rid of cyanobacteria from our drinking water. But when it’s warm and the water is rich in nutrients, the conditions are just right for harmful algae blooms!

During algae blooms it becomes almost impossible for water systems to provide us with truly clean water. Besides, even if they could remove all of the cyanobacteria and cyanotoxins, the water would still taste and smell bad – and the water treatment plants can do nothing about it!

According to the EPA, reverse osmosis is effective at removing cyanobacteria and cyanotoxins. Reverse osmosis is even effective at removing a particularly nasty group of them called microcystins, which are considered one of the most toxic!

11. Improves smell, taste and color

Ok, so reverse osmosis is able to remove almost anything it seems! But what about when your water tastes or smells funny? Or when it doesn’t look quite right?

Can reverse osmosis fix that?

It turns out that it can!

The special combination of multiple filters and the semi-permeable membrane that only a reverse osmosis system has is what makes it able to get rid of a TON of contaminants that would otherwise make our water taste, smell and look bad.

In case your water ever tastes, smells or looks nasty check out the information below – I have put together the most common contaminants and what they do to your water.

And don’t forget reverse osmosis can remove all of them.

ContaminantTaste Issue
ManganeseBitter, Metallic
SulfateSalty, or rotten egg
Total dissolved solids (TDS)Salty
ContaminantColor Issue
Foaming agentsCloudy
ManganeseBrown to black
Total dissolved solids (TDS)Varies
ContaminantOdor Issue
CyanobacteriaEarthy / musty
Foaming agentsVaries
SulfateRotten egg

12. Makes domestic well water drinkable!

More than 43 million people use a well for their drinking water(Ref 2).

Are you one of them?

I wouldn’t be surprised since according to the U.S. Geological Survey a whopping 15% of the U.S. uses domestic wells to get their drinking water!

Unfortunately, a study that spanned 13 years found that domestic wells across the country had contaminants at really high concentrations.

The most common contaminants were:

  • Bacteria
  • Metals
  • Nitrate
  • Pesticides

These are some seriously nasty things that you certainly wouldn’t want to drink. So it’s good that a reverse osmosis system can remove all of these contaminants.

But, the Office of Environmental Health recommends testing your water before using it for drinking or cooking! Besides, if you are like me you would want to know what contaminants are in your water anyway.

Amazon has a great range of testing kits – but they can be a bit confusing, because some test for a whole bunch of different contaminants, while others test for just one.

Really it comes down to 2 different types of tests.

  1. DIY tests
  2. Lab tests

1. DIY tests

The Do-It-Yourself water testing kits are affordable and easy to use. The best one that I found tests for 20 contaminants and you don’t have to be a scientist to figure out the test! You can check their latest price on Amazon here.

What I liked best about this tester kit is that it can detect bacteria and pesticides – while most other tests don’t!

2. Lab tests

Lab tests are way MORE EXPENSIVE than DIY tests. The test requires you to collect a water sample from your well and then mail it off to be tested at an EPA certified lab – So, I am not really surprised at the high price tag!

Then why would you bother if you can buy a cheaper test kit and do it yourself? Well, because a lab is always going to be more accurate than a home kit.

These lab tests are a great idea if you want to do a one-off test to find out what your groundwater is like in detail, or if you just moved to a new area or have just started pumping water from a new well.

Lab tests are also a good idea if you are worried that a contaminant might be close to the ‘safe drinking limits’.

You can check out the best lab test kit that I found on Amazon here.

This one is 9 times more expensive than the DIY test and there are cheaper lab tests available. But this is the only one I found that effectively tests for pesticides and organic compounds – plus all the other usual contaminants, like metals. In fact, it tests for 200 contaminants – while the DIY and cheaper lab tests often only detect 15 contaminants.

13. Improves city water

While reverse osmosis improves all types of water what I’m talking about here is city water, and more specifically city water that is sourced from groundwater.

According to the U.S. Geological Survey…

“About 115 million people—more than one-third of the Nation’s population—rely on groundwater for drinking water”.


Why is that important?

Because 1 of every 5 groundwater samples contains a contaminant at dangerously high concentrations.

Arsenic and nitrate are 2 of the nastiest contaminants that are often in groundwater at high concentrations. The problem is while the community and public water systems treat the groundwater to make it drinkable they DO NOT remove all traces of contaminants like arsenic and nitrate.

So that means the water at your house or condo probably still has arsenic and nitrate in it – and other contaminants.

Since reverse osmosis is able to remove all of these contaminants having a system at home gives you peace of mind that the water you are drinking is free from toxic metals and carcinogens.

14. Makes tap water safe to drink – EPA vs EWG

Surprisingly, not everyone thinks that the ‘safe legal limit’ for contaminants is actually safe! The current limits are set by the EPA – and they make them based on the Safe Drinking Water Act.

Even though these are federal drinking water standards the Environmental Working Group (EWG) says the contaminant limits are inadequate and outdated.  

Basically, the EWG thinks the limits for many contaminants are too weak, and tap water that is considered ‘safe’ to drink, is anything but!

So, what does this have to do with reverse osmosis?

Well, the community water systems that treat our water only reduce contaminants until they are below the limits set by the EPA and NOT the health guidelines suggested by the EWG.

Some of the contaminants the EWG are most concerned about are:

  • Arsenic
  • Chromium-6
  • Nitrate
  • Lead

This means the water in your home probably still has contaminants in it above the health guidelines. A reverse osmosis system can remove these contaminants and ensure you have CLEAN and SAFE water to drink at home.

If you are curious about how the tap water in your area checks out with the EWG guidelines you can check out their website here.

15. Require regular filter changes

Reverse osmosis systems do an amazing job of getting rid of all the different nasty things from our water. But that is because they have lots of different parts.

There are 3 important parts:

  • Pre-sediment filter
  • Carbon filter
  • Semi-permeable membrane

It is super important that these are changed regularly.

Why? It actually reminds me of that song “Dem Bones”, you know the one that goes…”Your knee bone’s connected to your thigh bone“.

Because the pre-sediment filter gets rid of sediments (duh!) like dirt, silt and sand, which prevents them from clogging up the next stage – the carbon filter.

Then the carbon filter removes chlorine (among other things) that would damage the next stage – the semi-permeable membrane.

And the membrane does most of the grunt work at making our water clean to drink.

So, that means a regular maintenance schedule is vital to having a FUNCTIONAL reverse osmosis system – and let’s face it, there isn’t much point in having one if it’s not cleaning water properly.

Plus, don’t forget a system sanitization and recharge should be completed ever year!

16. Can be expensive

Of course it’s pretty obvious from reason #14 that a reverse osmosis isn’t going to be a one-off cost. There is a lifetime of filter and membrane replacements to purchase.

Then there is the initial set-up cost too – although they come in 2 very different price brackets

  1. Point of Entry – $12,000 -$18,000 (installed)
  2. Point of Use – $60 – $200

The difference? Point of Entry will treat all the water in your house, while a point of use will just treat the water at the specific tap where you locate the unit.

Point of Use systems are great if you are only worried about clean drinking water and not fussed about the water that is in your shower or toilet.

So, yes – reverse osmosis systems are not free… but I still think they are way cheaper than bottled water and definitely a cheap way to guarantee your tap water is clean and safe to drink.

17. Can corrode pipes

I know, it sounds weird to say a reverse osmosis system can corrode pipes – well… technically it’s the treated water that does the corroding.

Water treated by reverse osmosis has had the calcium removed, this lowers the pH of the water – making it more acidic!

If you have old pipes at home the treated water flows through and can corrode them – leaching lead, copper and iron into your water.

The expensive solution to this is to have your pipes replaced.

But the easy and far cheaper solution is to have a Point of Use reverse osmosis system. Then the treated water won’t flow through all of your old pipes in your entire house before it comes out of your tap – perfect!

Also – it’s important to know, that if your pipes are old and made of lead or copper, then they are probably already leaching metals into your water anyway.

17. Are good for the environment

Yup, reverse osmosis systems are not only good for you, they are good for the planet too.

Reverse osmosis systems:

  • DON’T use electricity to purify the water – unlike other methods, like Distillation or Ultra Violet.
  • REDUCE the amount of bottled water purchased
  • Need filter changes LESS frequently than filter jugs or counter-top filters

So, that’s less plastic and less fossil fuels being burnt – go reverse osmosis!

18. Water purification can take time

No water purification method is instantaneous!

Reverse osmosis takes time – after all the water has to go through each filter and then be pushed through the membrane before it is ready to drink. Some systems even have more filters after the membrane!

The reverse osmosis system essentially slows the water flow down.

That is why each system comes with a water tank! Once the water is treated by the reverse osmosis it is stored in the water tank – ready for you to use.

Of course, that also means if you need a large amount of water that your tank might not be sufficient. But don’t worry – you can always buy a second water tank.

20. Removes Total Dissolved Solids

Total Dissolved Solids (TDS) are mostly naturally occurring minerals, but can also be heavy metals.

When water has high amounts of TDS it can often smell, look or taste bad.

Reverse osmosis systems remove between 90% and 95% of the TDS in your water.

If you want to know what the TDS in your water is you can test it easily at home – you can even test the water before and after your reverse osmosis has treated it!

There are 2 main types of TDS monitors

  1. Manual
  2. Automatic

1. Manual TDS monitors are exactly what they say they are – Manual! If you get one make sure it comes with Automatic Temperature Compensation (ATC), like this TDS meter by NovoBlue on Amazon.

Without an ATC, the temperature of your water temperatures can distort the TDS reading.

2. Automatic TDS monitors have in-line probes that attach to both the feed water and product water lines. This means you can switch between either line to get a TDS reading.

I really like this HM Digital in-line TDS monitor (Amazon link), it’s not overly expensive and it gets amazing reviews

Once you have your TDS reading you will know if your water is truly good to drink – A TDS of 0-50 ppm is IDEAL for drinking water from a reverse osmosis system.


Overall, reverse osmosis systems are one of the BEST ways to purify water. So, buying a reverse osmosis system is a great investment and if you need any of the items mentioned in this post you can access them through the links below.


Interested in learning more about reverse osmosis? Check out these other great posts:


1B C Hitzfeld, S J Höger, and D R Dietrich. Cyanobacterial toxins: removal during drinking water treatment, and human risk assessment. Environ Health Perspect. 2000 Mar; 108 (Suppl 1): 113–122.

2DeSimone, L. A., Hamilton, P. A., & Gilliom, R. J. (2009). Quality of Water from Domestic Wells in Principal Aquifers of the United States, 1991-2004: Overview of Major Findings (1332).

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