Should I Use a Reverse Osmosis System for Well Water?

Trying to decide whether or not a reverse osmosis system is suitable for treating your well water supply?

Here, we’ve shared everything you need to know about reverse osmosis for well water, including how the RO process works, which contaminants RO removes, and what to consider when choosing an RO system for well water.

🔎 What as a Reverse Osmosis System?

A reverse osmosis (RO) system is a type of water treatment system that uses a process called reverse osmosis to filter water.

RO systems have multiple filter stages, including a semi-permeable membrane, which work together to reduce the majority of TDS (total dissolved solids), including chemicals, pesticides, heavy metals, microorganisms, pharmaceuticals, and inorganic contaminants. They also remove the “good” stuff, like healthy minerals and salts.

A reverse osmosis system may be installed at your home’s point of entry (whole home RO systems) or at a specific point of use (under-sink RO systems or countertop units). The location of the unit determines whether it protects your entire plumbing system from contaminants, or whether it just filters your drinking water.

Most RO filters have a storage tank, which stores the filtered water so that it can be delivered to your faucet when needed. Some systems are tankless, which means they’re more space-saving, but you’ll have to wait longer to access purified RO water.

⚙️ How Does a Reverse Osmosis System Work?

A reverse osmosis system works by sending water through several filtration stages, which filter and purify water by removing different contaminants.

The filters found in a typical RO filter system are:

• A sediment filter, which removes sand, silt, dust, rust, and other sediment and debris that could block the later filter stages
• An activated carbon filter, which uses the adsorption process to trap chlorine, pesticides, tastes, and odors
• A semi-permeable membrane, which uses membrane separation to trap all impurities larger than 0.0001 microns while allowing water molecules to pass through
• A carbon post-filter, which polishes the water and removes any lingering contaminants

The reverse osmosis process requires high water pressure, so the system may come with a built-in booster pump, or you might need to buy a separate booster pump to increase your water pressure so that there’s enough power to send water through all the filter stages while minimizing waste.

Speaking of waste, RO systems do waste water during the purification process. As water is pushed through the RO membrane, the contaminants and impurities are rejected, bouncing back into the RO chamber. Here, the contaminants are flushed out of the system with a small amount of wastewater.

Depending on its efficiency ratio, an RO unit wastes on average around 1-4 gallons of water for every 1 gallon produced.

🧱 Is a Reverse Osmosis System Suitable for Well Water?

Yes, reverse osmosis systems are suitable for well water but there’s a catch.

However, these systems are predominantly designed for filtering city water, which has been pre-treated and doesn’t contain high concentrations of some of the contaminants that might be found in well water.

The RO membrane may become clogged with iron, hardness, and other contaminants that are commonly found in well water.

Plus, while RO does remove microorganisms, it doesn’t guarantee that water is microbiologically safe, and it doesn’t disinfect water. High concentrations of bacteria and other microorganisms could build up in the membrane and potentially re-contaminate the purified water.

So, while you can use a reverse osmosis system for well water, you may need to install a pre-treatment system that reduces certain contaminants or disinfects your water upstream of the RO unit.

🧫 What Contaminants Does Reverse Osmosis Remove?

Reverse osmosis systems can remove the majority of drinking water contaminants, including sediment, chemicals, microorganisms, metals, and minerals.

Check the below table to see which contaminants an RO system can remove from a drinking water supply.

Contaminant	Removal/Reduction %
Aluminum	92-98%
Ameobic-cysts	> 99%
Ammonium	84-95%
Arsenic + 3	69-80%
Arsenic + 5	93-99%
Asbestos	> 99%
Bacteria	> 99%
Barium	92-98%
Bicarbonate	89-95%
Boron	54-60%
Cadmium	92-98%
Calcium	92-98%
Chloride	89-95%
Chromate	89-95%
Chromium-3	93-99%
Chromium-6	93-99%
Copper	93-99%
Cyanide	89-95%
Detergents	97%
Fluoride	89-97%
Giardia	> 99%
Herbicides	97%
Herbicides	97%
Insecticides	97%
Insecticides	97%
Iron	92-98%
Lead	93-99%
Magnesium	92-98%
Manganese	92-98%
Mercury	92-98%
Nickel	92-98%
Nitrate	84-90%
Pharmaceuticals	80-99%
Phosphate	92-98%
Potassium	89-95%
Protozoa	> 99%
Radioactivity	92-98%
Sediment/ Turbidity	> 99%
Selenium	92-98%
Silver	92-98%
Sodium	89-95%
Strontium	92-98%
Sulfate	92-98%
Sulfur	97%
Total Dissolved Solids	94-99%
Zinc	92-98%

💧 Well Water Overview

Well water is different from municipal drinking water.

While municipal (or city) water is treated at the treatment plant prior to delivery to your home, well water is untreated and may need to be filtered, disinfected, or purified by you (or the homeowner).

Well water is typically drawn from an underground water source – usually an aquifer. That means the water has different properties and contains different contaminants to city water, which may affect the effectiveness of the RO process.

🔬 Common Well Water Contaminants

Some of the common contaminants found in well water are:

• Chemicals – Including nitrates & nitrites, from animal waste, sewage, and fertilizers
• Pesticides and herbicides – As a result of agricultural runoff and soil seepage from farmland
• Iron & manganese – Found in regions with soils and rocks with a high metal/mineral content
• Copper & lead – In homes with aging well/plumbing systems that contain old, corroding pipes and components made from these materials
• Fluoride – Found naturally in some regions
• Hydrogen sulfide – Occurs naturally as a result of sulfur-reducing bacteria in groundwater, gives water a rotten egg smell
• Hardness minerals – Present in most rocks and soils in the US, have aesthetic effects on pipes & plumbing
• Radionuclides – Including radium, radon, and uranium, found in many rocks and soils
• Microorganisms – Like bacteria and viruses, may contaminate wells as a result of septic system contamination or other nearby sources of human or animal waste

🤔 When Does RO for Well Water Require Pre-Treatment?

In the table below, we’ve shared the common well water contaminants, their possible effects on the RO membrane, and whether they’re addressed by RO or whether they need pretreatment.

Type of contaminant	Membrane effects	Pre-treatment required?
Chemicals	N/A	No
Pesticides & herbicides	N/A	No
Iron & manganese	Fouling	Yes
Copper & lead	N/A	No
Fluoride	N/A	No
Hydrogen sulfide	Fouling	Yes
Hardness minerals	Scale	Yes
Radionuclides	N/A	No
Microorganisms	Biofouling	Yes

The yes/no answers above aren’t definite for all situations. For instance, the presence of a very small amount of iron doesn’t instantly call for a dedicated iron removal system to be installed as a pre-treatment solution upstream of an RO system. However, if your water contains 2 PPM of iron or more, you’ll benefit from pre-treatment to prevent fouling of the membrane.

Certain microorganisms might not damage the membrane, but they may be small enough to slip through the membrane’s pores or cause biofouling and colonization, so you’ll need a pre-treatment disinfection unit that will eliminate these contaminants to make water safe to drink.

⚖️ Pros & Cons of RO Systems for Well Water

Let’s look at some of the key advantages and disadvantages of RO systems for well water.

Pros

• Removes impurities – Reverse osmosis removes virtually all drinking water impurities, from chemicals to metals to microorganisms.
• All-in-one solution – If you don’t require pre-treatment for your water, you can use an RO system as an all-in-one water purification solution. A whole-house RO system will protect your entire home from a range of harmful contaminants.
• Better than bottled water – Using an RO filter is cheaper and better for the environment than buying bottled water rather than drinking the water from your well.
• Most thorough treatment – Reverse osmosis is more thorough and comprehensive than any dedicated well water filter.

Cons

• Don’t guarantee microbiologically safe water – An RO system doesn’t disinfect water, so it doesn’t guarantee that water is free from all microorganisms.
• Membrane may be damaged by certain impurities – Iron, hardness minerals, and other common well water impurities may foul or clog the membrane, reducing its efficiency.
• Expensive – Even an under-sink RO system will set you back on average $500-$800, and a whole-house system costs thousands.
• Waste water – An RO system will waste water as it produces purified well water.

🆚 RO vs Dedicated Well Water Filters

Many people choose to use reverse osmosis water filters alongside dedicated well water filters for the most comprehensive water treatment.

However, the type of filters you use – and whether you use one or several – depends on your water quality and your intended outcome.

If you just want to remove a handful of common well water contaminants, or achieve a specific purpose (such as disinfecting your water), you don’t need a reverse osmosis water filtration system. You may as well save your money and buy the well water filter that treats the contaminants your water contains.

But if you want to achieve the highest-quality water possible, installing an RO system downstream of a dedicated well water filter will help you to achieve this. The pre-treatment system will remove the contaminants that are present in large quantities in your water, protecting the reverse osmosis membrane. The RO system will remove TDS and produce pure, clean drinking water.

Of course, your well water might be relatively low in all drinking water contaminants. In this case, you may not need to use any dedicated well water filter system, but you might still choose to use an RO system to produce purified water that’s guaranteed to be safe to drink. This is a good idea since well water isn’t treated by a water supplier to make it safe and clean before it reaches your home.

📝 What To Consider When Choosing An RO System For Well Water

Here are some of the things you should consider when you’re deciding on an RO system for your well water.

Your Well Contaminants

First, test your water (if you haven’t already) to find out what it contains.

RO water filters remove the majority of TDS, but if your water only contains a few contaminants, it might make more sense to spend less on a dedicated well water filter.

Your Budget

The RO filtration process is incredibly thorough – and you pay more for the purified water you’ll receive.

You’ll need a budget of at least $400 for a point of use RO system, or a minimum of $5,000 for a whole house RO system.

Pre-Treatment

If your well water contains certain contaminants, like iron, manganese, or hardness minerals, you’ll need to install a pre-treatment system.

This filtration system should remove the problem contaminant upstream of the RO system, preventing membrane damage.

Water Flow/Pressure

A reverse osmosis system will reduce your water pressure somewhat. RO systems also need high water pressure to send water through all the filter stages while minimizing water waste.

Many households on a private well have low water pressure. If water pressure is an issue in your home, you may need to install a pressure booster pump to prevent excess wastewater production and provide sufficient water flow to your fixtures and appliances.

Water Waste

As we mentioned, RO filters produce some water waste.

You need to be comfortable with this before you buy an RO system. If not, you might want to consider a non-RO alternative.

The best RO systems have 1:1, 1:2, or even 1:3 waste-to-pure water ratios, meaning that only 1 gallon of water is wasted for every 1-3 gallons of pure water produced.

Installation & Maintenance

Installing an RO water filtration system takes some effort. You’ll need to hook the system up to your water line, install a drain line, and attach the storage tank (if you have a conventional tank-based system).

Maintenance is simple, but regular maintenance is essential to sustain the system’s performance. You’ll need to buy multiple replacement filters per year to continue to effectively remove contaminants from your well water.

Additional Water Treatment

Depending on what your water contains, you may need additional water treatment upstream or downstream of the RO system.

This includes disinfection (such as with a UV filter) an remineralization with an alkaline filter post-RO treatment.

Whole-House Vs POU

Whole-house RO systems are gradually becoming a more popular choice. However, they’re still nowhere near as popular as point-of-use reverse osmosis systems, like under-sink and countertop systems, which are cheaper, less wasteful, and much smaller.

If you just want to improve the quality of your drinking water, choose a POU RO system. Keep in mind, though, that if your well contains aesthetic contaminants like iron, you’ll have to install an additional POE (point of entry) system that will remove these impurities to protect your plumbing system.

Whole-house RO systems are a viable option for well water. But if you use reverse osmosis to treat your entire home’s water supply, you’ll waste much more water than you would with a countertop or under-sink RO system that only treats water at your kitchen sink. Plus, a whole-house RO system is very expensive, costing upwards of $6,500 on average.

🔚 Final Word

Reverse osmosis is one of the most thorough, comprehensive water treatment solutions, so it’s ideal for making well water clean, pure, and safe to drink.

RO systems can be used with well water, but more often than not, you’ll need to first install a dedicated well water filter at your main water line, which will protect the semi-permeable membrane from fouling.

❔ FAQs

Is reverse osmosis good for well water?

Yes, reverse osmosis is good for well water because it removes virtually all impurities, making water clean and safe for drinking. This is especially important for well water, which isn’t filtered or treated by a municipal supplier. However, you may need to install a pre-treatment filter if your well water contains contaminants that could damage the RO system’s membrane.

Does reverse osmosis work for hard well water?

Yes, reverse osmosis works for hard well water, but we don’t recommend using RO as a dedicated hardness treatment. The problem is that excess calcium and magnesium minerals will result in scale formation in the membrane, blocking its process and reducing its efficiency. The membrane will clog at a faster rate, and you’ll need to replace it more frequently. We recommend a water softener as a dedicated water hardness treatment.

What is the best way to filter well water?

The best way to filter well water is to address the contaminants that are present in your water. These could include iron, manganese, nitrate and nitrite, sulfur, microorganisms, and hardness minerals. Focus on removing these minerals first; then, if you want to further purify your water, consider installing a reverse osmosis filter system.