Reverse Osmosis is the most complete and cost effective water filtration process (in relation to contaminants removed) that you can have for your house. It
does have a high initial cost, most likely requires electricity to pump the water through your house, and might need more routine maintenance than a carbon whole house filter. Like any whole house filter, you will probably also need to hire a plumber for the initial installation depending on your experience and comfort level.
Because a whole house reverse osmosis system can cost double the amount of a carbon whole house filter, this might only be an option if you are on well water with poor water quality or very serious about having the best, most pure water available.
If your current budget does not permit a whole house RO filter, please consider an undersink RO filter for drinking and cooking or a carbon whole house filter.
What is Reverse Osmosis & How Does It Work?
Reverse osmosis was first developed in the 1950’s as a way to desalinate sea water to turn it into fresh water to solve water shortage issues. The technology has come a long way and also greatly reduced in cost so it is an affordable option for household use. It is also used by several bottled water producers as well.
Reverse Osmosis works by pushing water through a semi-permeable membrane that rejects any particles larger than .001 microns. A carbon filter can only filter out particles up to .5 microns and absorbs it’s contaminants. The opening is small enough for the water molecules to pass through and will remove up to 98 or 99% of most water contaminants that are larger in size than .001 microns that are discharged through a waste channel.
What Do Reverse Osmosis Filters Remove?
Reverse Osmosis filter will not remove everything from water, like distillation, but they are the most cost-effective & complete filtration method available that will deliver a consistent supply of water.
Before the water reaches the RO semi-permeable membrane, the water needs to pass through carbon block filters for chlorine to be removed. Otherwise the membrane will be destroyed. The carbon filters also remove VOC‘s (Volatile Organic Compounds), pesticides, and herbicides that the membrane isn’t the most effective at removing.
Once the water reaches the thin-film semi-permeable membrane, it is certified to remove the following contaminants:
- 98% Chlorine
- 98% Arsenic
- 99% Lead & Asbestos
- 96% Fluoride
- 96% Mercury
- 97% Chromium
- 99.9% Cysts
- 96.5% TDS (Total Dissolved Solids)
If you have a salt-based water softener, the sodium does reduce the effectiveness of the membrane filter. Depending on the amount of sodium and the pH level, the amount of lead removed can only be 90-95% instead.
Type Of Filters With A Reverse Osmosis System
For the reverse osmosis filter to function correctly, you need more than the semi-permeable membrane filter. Otherwise the chlorine and other contaminants would immediately destroy & clog the membrane. Instead you need a multi-stage filtration system. With 3 stages being the minimum, but most everyone recommends a 5 stage filtration system for optimum performance. You get the most contaminants removed with restricting your output flow.
Depending on the brand, the sediment and carbon filters will need to be changed every 6 months to one year. The membrane will need to be replaced every 3-5 years. Some more heavy-duty membranes can last up to 10 years before needing replaced.
Here is a walkthrough of a 5-stage filtration system:
- Stage 1: Sediment Filter that removes visible dirt, rocks, and rust. Prevents carbon & membrane filters from getting clogged.
- Stage 2: Carbon Block Filter that removes chlorine, VOCs, pesticides, herbicides, tastes, and odors.
- Stage 3: Carbon Block Filter that further removes the contaminants that passed through the Stage 2 carbon filter.
- Stage 4: Semi-permeable membrane that is composed of two plastic films, cellulose acetate and polyamide. Both of these complement each others strengths and weaknesses to filter out Total Dissolved Solids and contaminants like arsenic, lead, fluoride, and chromium.
- Stage 5: Post-membrane carbon filter that removes any odor or taste remaining after passing through the membrane.
- Stage 6 (Optional): Mineral and/or UV Filter that puts healthy minerals back into the water and the UV light will further remove any presence of bacteria or viruses that might have passed through the previous filters.
There are some 6-stage filters available. The 6th stage can be a mineral filter that adds calcium and magnesium back to the water, as RO filters out any nutrient in addition to the contaminants. Or the additional filter can be a Ultraviolet (UV) light that will kill any remaining viruses or bacteria. The UV filter is normally recommended if you are on well water or just want extra piece of mind.
Both of these filters do cost extra money and can potentially reduce the water flow departing the membrane.
Money Saving Tip: If you are concerned about the nutrients being removed from your water, you can add a teaspoon of pink Himalayan salt per every filtered gallon of water to restore the mineral nutrients.
What Equipment Is Needed For a Whole House RO Filter?
First off, a whole house RO system needs a lot of space. You are going to want to put it in your basement or garage. There are 3 items for sure that are required for a whole house system:
- Reverse Osmosis System– This is the “brain” of the system that contains the filters.
- Atmospheric Storage Tank– Holds around 100+ gallons of filtered water.
- Variable Speed Pump- What pushes the water through the house so you get a desirable flow.
There are some smaller whole house RO systems that do not require pumps, that might meet your household needs.
Most of the systems recommended for whole house applications are billed as commercial grade and require a pump. They are higher-quality fittings and equipment, usually made in the USA, that will last longer and you have less chance of developing leaks.
Also be sure to get a metal atmospheric storage tank. Plastic ones are available at a reduced cost but more subject to breakage and loss of pressure. Regardless of the tank you use, the water is held in a plastic bladder so it will never come into contact with the tank walls. This also means if you have a metal tank, then rust or corrosion will not leach into your water.
What Size System Should I Get?
Gallons Per Day
You will also need to factor in how much water you plan to consume on a daily basis. All RO systems are rated by filtered gallons per day. It is recommended to get a system that is double the amount of water you normally consume. For example if you consume 200 gallons per day, then it’s recommended to get a system rated for 400 gallons per day.
For example, a system is rated for 400 gallons per day but if you use around that same amount daily, you will need to get a higher rated system. It will not be able to deliver a consistent flow rate if you consume close to the maximum capacity.
Similar to water softeners, RO systems discharge the waste water that contains the contaminants that were blocked from the membranes. Base models can have a waste ratio of 1 waste gallon: 1 filtered gallon. More efficient systems have a lower ratio of 1 waste gallon: 3-4 filtered gallons.
The Best Place To Buy A Whole House RO System
There are not that many companies that produce whole house RO filtration systems and most are marketed for commercial use.
The two brand names that I have most commonly seen are:
Crystal Quest (You can get their entry level filter rated at 500 gallons per day for approximately $2000 plus the cost for the storage tank & pump).
U.S. Water Systems (All-inclusive filter system that includes storage tank and pump and the basic model costs approximately $5,000 on sale).
There are other reputable brands as well, but the two mentioned above that use quality materials.
What If A Whole House RO System Isn’t For Me?
If for some reason a whole house RO system isn’t the best option for your household, but still want a reverse osmosis system, I recommend getting an undersink filter. This way you can filter your drinking and cooking water. You can get a quality undersink point-of-use filter for approximately $300. You can also get a filtered showerhead for around $30 every 6 months to address unfiltered bathing water.
If you still want a whole house filter, a carbon filter will greatly improve your water quality at a cheaper overall and ongoing cost.