8 things to consider when buying an RO system

1. Water source

The water that enters your home feeds the reverse osmosis system. City water or municipally treated water is relatively free of chemicals and bacteria but may contain inorganic dissolved solids, which an RO system is designed to reduce. Private well water could contain harmful pathogens and chemicals in addition to dissolved solids.

Reverse osmosis systems can treat both city and well water, as long as the well water has been pretreated for bacteria and particles that could clog the membrane. If you’re on well water contaminated with heavy metals like arsenic, then you may need a UV system to disinfect the water once it leaves the storage tank.

2. Water demand

Consider how much water you and your family are going to use. Every person, according to nutritionists, should drink half their weight in ounces every day. So, if you weigh 160 pounds, then you should be drinking 80 ounces of water per day. You also have to take water used in ice machines, refrigerators, and all your other appliances into account. Each reverse osmosis system provides the amount of water produced each day, measured in GPD (gallons per day).

3. Water pressure

Reverse osmosis uses water pressure to force clean water through the membrane. If your household water pressure is below 40 psi, then you need to increase the pressure for reverse osmosis with an RO booster pump. If you're on well water supply, make sure your tank’s water pressure is set high enough for an RO system to work. A high level of dissolved solids in water also increases the amount of pressure needed for the RO system to produce clean water.
A residential reverse osmosis system is point-of-use, which means you install it right where you need the RO water. Most RO systems install directly under your sink. Whole house reverse osmosis systems are used less often because they require a large storage tank and booster pump for adequate pressure to supply water to every point in your house.

4. RO style

Reverse osmosis systems come three different cartridge styles: quick-change, drop-in, and standard. Your choice of filter style depends on whether you prefer easy maintenance, low maintenance cost, or the least environmental impact.

Quick-change cartridges: simplest to maintain, but also the most expensive and the least environmentally friendly

Quick-change filters are easy to replace. Simply twist the filter and pull it out. Then, take the new filter and turn it in the opposite direction to replace the old one. However, the ease of maintenance comes with a high price tag, and the filter cartridges are made of plastic that gets wasted every time an old filter is discarded.

Drop-in and standard cartridges: More difficult to replace, but also the least expensive and most environmentally friendly.

To replace a drop-in or standard filter, unscrew the housing, throw the filter cartridge away, put a new cartridge in, and put the housing back in its place. Standard filters can be replaced with compatible cartridges, but drop-in systems require exact replacements.

Reverse osmosis systems also come in different stages, usually three, four, or five, based on the number of prefilters and postfilters included. The RO membrane does most of the work removing dissolved solids, but additional prefilters and postfilters can polish, re-mineralize, and provide additional chlorine and sediment removal. Eventually, the membrane wears out, but prefilters give an initial pass through filter media to help extend the life of the membrane.

5. Budget

When budgeting for a reverse osmosis system, you have several factors to consider: How much does the system cost? How much will installation cost, especially if you hire someone? How much does on-going maintenance cost? These factors may affect which RO system you choose or whether or not you use one at all.

The price of a reverse osmosis system varies depending on whether you need one under your sink or for your whole house and how many additional components you need. Whole house RO systems are much more expensive and complex. Under-sink RO systems usually range from $200 to $400 depending on the style. The cost increases if the system includes a booster pump, permeate pump, storage tank, or pretreatment.

Installing any RO system is an investment that requires on-going maintenance costs, including replacement filters and membranes. The replacement cost and frequency depend on your style of an RO system. Generally, the RO membrane needs replacing every two years, and the filters need replacing every six months to one year. The reverse osmosis system itself lasts twenty years or longer with proper care.

Factors that influence the cost of an RO system:

  • Type of system
  • Pretreatment
  • Installation cost
  • Maintenance cost
  • Additional components

6. Ease of Installation

Most under-sink reverse osmosis systems are easy to install. However, installing an under-sink RO system requires a dedicated faucet, which means you may have to drill a hole in your countertop. If you're not comfortable doing this job yourself, then you may need assistance from a plumber or a handy friend or family member.

Reverse osmosis systems must have a dedicated faucet and a drain connection to prevent the dirty drain water from flowing back into the clean drinking water. An RO system cross-connects the drain line and the water line. Plumbing code requires that cross-connections have an air gap faucet that allows drain water to pass through without returning to the clean water.

Consult a water specialist before installing a whole house reverse osmosis system to make sure there's not a simpler, equally effective solution and to make sure you apply proper pretreatment based on your water conditions.

7. Efficiency 

A reverse osmosis system is not the most efficient filter. After reverse osmosis filters contaminants, it sends them to the drain with a significant amount of water. However, this water is not exactly wasted since it's used to carry contaminants away and make potable water.

Standard water filters collect contaminants on their surface, but the RO membrane stops them and uses water to carry them to the drain. Adding a permeate pump to your RO system makes it 85% more efficient. The permeate pump uses the wastewater as energy to send clean water to the storage tank. The most environmentally friendly RO systems include a permeate pump or allow you to add one.

8. Remineralization

Reverse osmosis removes dissolved solids from water and reduces alkalinity or lowers water's pH in the process. The lower pH makes the water slightly acidic. Acid water is corrosive, but adding an acid neutralizing filter, like a calcite filter or alkaline water filter, increases the pH adds mineral flavor. The Aptera filter dissolves calcium and magnesium in water and reduces scale, microorganisms, and sediment through several stages of remineralization.


Posted by John Woodard on February 12, 2022

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