Water quality is an issue that affects every living thing on earth. Unfortunately, that quality is not always up to the level that we would wish, particularly in certain cities in the US and especially in third world countries. Those who are unfortunate enough to live in such places (or who simply want their water to be a little purer) might be considering the use of reverse osmosis as a method of home water purification. This topic can be a little confusing, so let’s see if we can give you a good primer.


What Is Reverse Osmosis?

Reverse osmosis is a process by which contaminants are removed from drinking water, and it seems to be one of the most effective ways to do so. It can even turn salt water from the ocean into fresh, drinkable water. In fact, that was its original purpose. There are certain areas that don’t have a lot of fresh water but which do have access to the ocean.

According to watermasterz.com, reverse osmosis systems use pressure to force water through a semi-permeable membrane. “Semi-permeable” means that only certain things can pass through. You see, water molecules are actually very small compared to the molecules that make nearly all contaminants. That means a fine enough filter will allow only water molecules to pass. This is the key principle by which reverse osmosis works.

This process also takes advantage of the scientific principle of osmosis. Chemists learned long ago that solvents have a tendency to concentrate on one side of a semi-permeable membrane. While they used this method to deliberately concentrate solvents, reverse osmosis uses the same principle to remove solvents and other water contaminants. The pressure is simply used to speed the process and make it more efficient.

What Are Those Semi-Permeable Membranes Made Of?

As you can see from above, the semi-permeable membrane is the heart of the whole operation. It has to be replaced from time to time, so that is a little bit of a limitation. Can you make or improvise these filters in a DIY fashion? Probably not. They are generally made of cellulose triacetate (CTA) or polysulfone.

The thing that makes reverse osmosis membranes unique is the fact that their openings are large enough to let water molecules through but small enough to keep out everything else. Because we are talking about nano-measurements here, you probably cannot replicate that level of precision at home. As you can see by reading the information linked above, some types of filters use even smaller pores than reverse osmosis filters.

How Effective Is Reverse Osmosis?

RO systems are widely used in countries that mostly consist of desert environments. Their best source of water is the sea, so they do quite a lot of this. The fact that these countries can provide enough water for their people through reverse osmosis filtration proves that it is indeed an effective method. But, let’s see if we can find some specifics.

Here is an interesting study which connects to an interesting case. In Nevada’s Lahontan Valley, the local groundwater is sometimes contaminated with arsenic. This contamination is not artificial but comes from deposits of natural arsenic within the ground. In any case, arsenic is highly lethal, so a lot of the residents took to purifying their water with reverse osmosis.

According to our study, these systems were able to remove (on average) 80.2% of the arsenic in the water. Well-maintained systems removed around 95%. Considering that the arsenic levels were not all that high in the first place, that’s pretty impressive.

Should I Use A Reverse Osmosis System In My Home?

For most people, it is probably not the most practical solution. Reverse osmosis is indeed one of the best methods of water purification, but it does have a few problems. First of all, it produces a lot of wastewater. For every one gallon of drinkable water produced, you might be disposing 5-6 gallons of wastewater. This wastewater has to go down the drain, and the concentrated contaminants will make it harder for someone else to purify that water down the line.

Apart from that, reverse osmosis will require you to stock up on filters. Their usefulness in an emergency/survival situation is definitely reduced when you consider the fact that you cannot make your own replacement filters. Speaking of cost, a reverse osmosis filter will also raise your water bill.

For these reasons, we would only recommend reverse osmosis water filters to those who really need them. They are indeed the most effective means of water purification known to man, but not everyone needs that serious of a solution. If your local water quality isn’t that bad, a simple carbon filter might be enough. If you live in an area with poor-quality/contaminated water (like those people in Lahontan Valley), we would definitely recommend reverse osmosis in spite of its limitations.


In many cases, companies that sell reverse osmosis systems will try to dazzle you with the benefits instead of simply telling you the facts. We have endeavored to do the exact opposite and give you all the information you need. You should now be able to fully understand the process, how it works, why it works, and whether or not you need a reverse osmosis system in your home.