Reverse osmosis (RO) can produce substantially cleaner water than a low-cost Brita-style filter, but it is not the right choice for every household. Carbon filtration can improve taste and odor and may adsorb some volatile organic compounds, while RO can remove contaminants such as PFAS, lead and arsenic. The trade-offs include water waste, filter costs, mineral removal, electricity requirements for some systems and potentially professional installation.
Carbon filters generally make water taste and smell better, but RO removes a broader range of contaminants. RO cannot capture everything, and carbon filters can still help remove certain volatile organic compounds through adsorption. Most RO systems also include an additional carbon filter.
Tank-based and tankless RO systems
There are two main types of RO systems. Tank-based systems filter water slowly, passively and without electricity, then store it in a fairly large tank beneath the sink. Tankless systems have become more popular because they treat water on demand, but they require electricity to move water quickly. Their added complexity makes them considerably more expensive.
What are the real risks of contaminants in water today?
“Tap water in the United States is safe for most people, most of the time,” says an industrial water-treatment veteran. Tap & Air, a website that monitors water and air quality in hundreds of municipalities, describes the problem as local rather than universal.
The first step in assessing your personal risk is to find out whether your household water meets standards. You can search online for the latest reports from your local water supplier. The Safe Drinking Water Act requires local water systems to issue an annual report on the quality of the water they provide by July 1 each year.
These reports can be extensive, so Voll recommends focusing on three main indicators: lead, nitrates or arsenic, and PFAS, the so-called “forever chemicals” used in nonstick cookware and other products. Lead and arsenic are serious hazards but are relatively uncommon today, while PFAS is a significant national concern. Voll said that at least one PFAS compound has been detected in the water supplies of 98 of the 200 largest cities in the United States.
RO systems can treat PFAS, lead and other compounds. Carbon filters generally cannot remove PFAS.
“Most people don’t need an RO,” Voll says. “But some homes clearly need it. The way to tell is to first read your water report.”
What are the disadvantages of using an RO system?
RO systems have several drawbacks, many of which are related to cost.
- RO wastes water: The technology has historically required large amounts of untreated tap water to produce relatively small amounts of purified water—sometimes up to four gallons of tap water for every gallon of clean water. In recent years, efficiency has improved considerably. Some systems can produce up to three gallons of clean water from four gallons of tap water, a 3:1 pure-water-to-wastewater ratio.
- Replacement filters are expensive: Depending on the application, an RO system may use as many as six filtration cartridges, typically replaced every one to two years. Like printer ink, these ongoing costs can be easy to overlook when buying the system. Replacement cartridges commonly cost $50 to $200 per year, so check prices before purchasing.
- RO removes beneficial minerals: Calcium, magnesium and potassium cannot pass through the RO membrane. RO systems also remove fluoride, which some users do not want and dentists generally do not favor removing. Some systems offer remineralization or pH-boosting cartridges, but those add to replacement costs.
- Installation may require professional help: Water leaks can cause serious damage, so professional installation may be worthwhile. Most RO systems also require a dedicated faucet. If your countertop does not already have an unused opening, installing that faucet may require drilling a new hole.
Do you need an under-sink RO system?
In the example discussed here, the local water report did not indicate a need for an RO system to address dangerous contaminants. However, the water supplier uses chloramines as disinfectants, and chloramine-treated water can have a slightly unpleasant taste when consumed directly from the tap. That issue is intensified by the region’s high water hardness. Much of this part of Texas is built on limestone, and the resulting calcium carbonate can give the water a slightly bitter flavor.
The local water report therefore points to taste, rather than a clear safety concern, as the main reason to consider RO in this case.
Here, RO is primarily about improving the taste of the water. Any residual contaminants removed in the process are an additional benefit.
Waterdrop X12 Under-Sink Tankless Reverse Osmosis System
The Waterdrop X12 was tested during an installation in which a plumber removed the old unit beneath the sink and replaced it with the higher-end system. The work took less than an hour.
Under-sink RO systems operate separately from a home’s existing plumbing and typically use three color-coded tubes. One connects to the water supply through an adapter valve, another connects to the wastewater drain using the included fitting, and the third connects to the dedicated faucet.
Although these connections may be manageable as a DIY project—particularly when replacing an existing system—an even minor leak can cause serious damage. Professional installation can provide additional peace of mind.
Source: www.wired.com
