The five steps will help you pick the water filtration system that best fits your needs

1. Find out what's in your water.Before you choose a filtration system, you need to know what it is you are looking to remove. You can get a copy of your area's annual water quality report from your water utility. You can also go a step further and test the water yourself, either using an at-home test kit (available at most home improvement stores) or getting in touch with your water utility to find a local lab. At the very least, you want to know if your water contains lead, but any additional information you can gather would be helpful.

2. Figure out what type of filter you need. Activated carbon filters, the type found in many water pitcher filters and undersink models, can remove heavy metals (like copper, mercury and lead), chlorine, pesticides, parasites (like giardia) and some VOCs. Other contaminants must be removed using a different type of purification system — perchlorates (the chemicals used in dry cleaning) can be removed only by reverse osmosis, and arsenic must be removed through distillation. NSF International, an independent, accredited organization that helps set standards for water safety and tests and certifies systems, has a comprehensive chart that specifies the type of filter you'll need to remove the contaminants in your water.

How the most common methods work: 

• Carbon filter: Activated carbon is found in pour-through water filtration pitchers and in many undersink filtration systems. Carbon filters work by trapping contaminants in the pores of the positively charged, highly absorbent filter.
• Reverse osmosis: A reverse osmosis system reverses the natural flow of water, passing the water through a semipermeable membrane. Be aware that this method does waste water.
• Distillation: Distillers heat water to the boiling point, then collect the steam as it condenses, leaving contaminants behind. Some contaminants that can convert to gas form will still remain in the water after distillation — you can combine a distiller with a carbon filter for better results.

3. Decide the filter's location. You can choose either a whole-house (also called point-of-entry) filter, which filters the water before it enters your home, or a point-of-use filter, which filters the water just before you use it. Point-of-use filters include faucet and undersink systems, pour-through water pitchers and water bottles.


Whole-house models are most often used to remove mineral deposits and unpleasant odors or tastes; you would still need to supplement a whole-house filter with another type to remove other contaminants. If excessive chlorine in your water bothers your skin, you may also want to consider a filter that attaches to your showerhead.

Undersink or water pitcher: Which to choose? Undersink models tend to work more effectively than water pitchers and bottles, thanks to the added pressure forcing water through the filtration system — and you have the option of choosing a reverse-osmosis filter. Undersink models have the added benefit of filtering as you use, so there's no need to remember to refill the pitcher, but they are also more expensive to install. 

So what's the bottom line? If you are looking for a quick, inexpensive solution (or you are a renter) and a carbon filter is all you need, a water pitcher is the way to go. If you are looking for a more permanent solution, or need more filtration than an activated carbon filter offers, get an undersink model.

4. Find a filtration system that is NSF certified. The single most important thing to look for when you are shopping for a water filtration system, whether it is for your whole house or it's a simple pitcher, is that it is certified by NSF International — when you see the NSF seal, that means the product or system has been tested to ensure it actually removes the contaminants it claims to remove. If you need help finding a water filtration system that is certified for the contaminants in your water, try using the search feature on the NSF site.

5. Inspect your current system. If you have a water filtration pitcher or other purification system that was purchased many years ago, it may be time for an upgrade. Regulations have changed in recent years, so you may have purchased a system that made inflated claims — look up the model number on the manufacturer's website to check for the most current information. Older Brita pitchers, for instance, claimed they filtered lead, but they do not meed NSF standards for lead. The ZeroWater filtration pitcher is currently the only pour-through pitcher on the market that's NSF certified to remove lead from tap water.

Maintenance: Change those filters! Once you have installed a water filtration system or purchased a new water filter pitcher, you need to regularly change the filters and keep everything clean and running smoothly. If your system does not include an automatic timer or sensor to let you know when you are due for a new filter, make sure you note the date on your calendar. Changing water filters promptly according to the manufacturer's recommendation is the best way to ensure that your water is being thoroughly cleaned.

Tell us: Do you filter your water? Have you ever tested your water? Please share your experiences in the Comments.