Filtering your drinking water is a good step to take to protect children’s health from pollutants in tap water. But understanding the pros and cons of different types of filters can be tricky.

A reverse osmosis water filter can remove a wider range of pollutants than other types of filters. But what else should parents know about reverse osmosis filters?

What pollutants do reverse osmosis filters remove from drinking water?

Reverse osmosis filters remove contaminants from drinking water by pushing them through a membrane with tiny pores that blocks particles larger than water molecules.

Typically, they also come equipped with a carbon filter that helps with initial purification and extends the useful lifetime of the reverse osmosis filter itself. The carbon filter also reduces the levels of some contaminants that cannot be removed by reverse osmosis alone, such as disinfection byproducts and volatile organic compounds.

Reverse osmosis reduces chemical contaminants that carbon filters cannot effectively reduce, such as:

  • Nitrate, which causes birth defects or, in higher doses, can be immediately toxic to babies.
  • Perchlorate, which changes the thyroid function and harms children’s brain development.
  • Arsenic, which impairs children’s growth, brain development and immune system.
  • Hexavalent chromium, which can have impacts that children are more susceptible to, such as harm to the reproductive system and risk of cancer.

Reverse osmosis reduces other contaminants that can also be reduced by a carbon filter, such as lead, which harms children’s brain development, and the toxic fluorinated chemicals known as PFAS.

What are the drawbacks of reverse osmosis filters?

Reverse osmosis systems tend to cost more than other types of filters and require installation under the sink. For many families these costs, plus the cost of replacement cartridges, can be a significant barrier.

Reverse osmosis systems also tend to waste water, about three times as much as they treat. To conserve water, reverse osmosis systems should be used to treat water used for drinking and cooking only, not as a whole-house filter. Timely maintenance and upkeep of the system also helps to minimize water waste.

If you’re shopping for a whole-house filter system, it’s important to remember that such systems remove residual levels of chlorine from the entire plumbing system in the house. With no disinfectant in the water, bacteria may grow in the household pipes between the filter and the tap. That’s another reason experts recommend installing reverse osmosis filters at the tap, rather than a whole-house filter.

What about minerals and fluoride?

Reverse osmosis removes contaminants, but also some necessary minerals, such as magnesium, calcium and iron. Foods cooked using reverse osmosis-treated tap water should not be a problem. But if mineral levels are a concern for you, or if you simply like the taste of added minerals, you can add them back with mineral drops, a special filter or a pitcher.

These filters also remove the fluoride from drinking water. There is growing evidence that too much fluoride in water can be harmful to children’s brain development. For the dental benefits of fluoride, such as preventing tooth decay, fluoride-containing toothpaste is a better alternative.

How to choose the right water filter

First, research your drinking water and find out what pollutants are present. You can find your water system and contaminant health guidelines in EWG’s Tap Water Database, which has just been updated. If you have a private well, consider getting your water tested.

Use EWG’s Water Filter Buying Guide to select the right filter for your family. Different contaminants can be removed by different types of filters. Click here for a Step-by-Step Guide to Selecting a Home Tap Water Filter.