How to Install a Whole-House Water Filter: A DIYer’s Guide

If you're concerned about contaminants in your home water supply, a whole-house water filter will help you breathe easier by delivering water that tastes better and is safer for you, your water heater, and the other water fixtures in your home. A water filtration system removes sediment that can settle to the bottom of the water heater tank; hard water minerals that can clog every faucet in the house; and metals, like iron and manganese, that discolor drinking water and give it a metallic taste.

Installing a whole-house water filter is a much more efficient way to guarantee good water quality than installing a filter on every faucet, but it doesn't necessarily eliminate the need for those smaller filters. It all depends on the quality of the water delivered to your house and the type of filtration system you install. Not all whole-house filters can remove both chlorine and chloramines from municipal water, for example, and you sometimes need extra filtration to get rid of the chlorine taste.

There are several water purification methods, and they can be used separately or combined into a single filtration system. You might think this would complicate installation, but it doesn't. In most cases, installing a whole-house water filter is actually a fairly simple DIY plumbing job. It becomes even simpler if you make the connections with PEX tubing, which is flexible, easy to use, leakproof, and practically indestructible. You can use PEX even if your current water pipes are copper.

A water filter has to do more than one job. It has to remove sediments, like sand, silt, dirt, and scale, which are more likely to be in well water than municipally supplied water. It has to filter out bacteria and other contaminants. It must remove minerals, like calcium, sulfur, iron, and manganese, and it should make the water taste better by removing chlorine and chloramines. Different filtration systems have been developed for each purpose:

• Sediment filters are typically mesh screens that capture large particles. They can be made from paper, polypropylene, or cellulose, but most contemporary ones use zeolite media. Zeolite is a volcanic rock with a high pore density. A zeolite pre-filter captures sediment before it enters more parts of the filtration system, and these particles are removed by draining or backwashing the media.
• Carbon adsorption is the most common filtration method. An activated carbon filter can remove microscopic particles as well as large molecules to deliver better-tasting and safer drinking water. A standard carbon filter can remove chlorine, but if your water company uses chloramines, you may need to upgrade to a catalytic carbon filter to get rid of them.
• Ion exchange filter media are commonly used in water softeners as well as water filtration systems. They employ electrically charged resin beads that attract minerals, such as calcium and iron.
• Oxidation reduction, or redox, filters employ manganese dioxide as an oxidizer to precipitate iron, hydrogen sulfide, and manganese out of the water. Redox filters are recommended if you have high-mineral well water.
• A reverse osmosis system uses the building's water pressure to force water through a membrane to an area of lower solute concentration, which is the opposite of how osmosis usually works. It's used more frequently on filters for individual faucets than for whole-house filters.
• UV purification systems can be installed in conjunction with whole-house filters to kill bacteria and other pathogens. They are usually installed at the end of the filtration system.

A whole-house water filtration system may contain one or more cartridges to take advantage of these different filtration methods. The cartridges are typically connected to a manifold (aka a central unit) and are installed together, making a multicartridge system no more complicated than one with a single cartridge for installation by a plumber or DIYer.

Your existing water system may already be plumbed with PEX (cross-linked polyethylene) tubing, but even if you have copper pipes, you can use adapters to switch. Besides being bendable and easier to work with than copper, PEX isn't damaged by ice and is the best plumbing option if there is any danger of freezing pipes in the winter. There are several methods to connect PEX tubing, including compression fittings and expansion connections, but the two most common are crimp rings and push-fit connections.

Push-fit connectors are convenient — just push in the tubing as far as it will go and you're finished — but they are expensive, so it's usually more economical to purchase barbed fittings. The catch is that you need a special crimping tool for the ring that holds the tubing to the connector, and if this is the only plumbing work you plan to do, you may not want to purchase one. However, considering that you are installing your own water treatment system, there's a pretty good chance you'll be doing more plumbing with PEX in the future, so a crimping tool may be a good investment. While you're at it, you should also get a PEX tubing cutter so you can get clean, straight cuts with little effort.

You need an accessible location for your whole-house filtration system because you have to periodically remove the filter housing or filter cartridge — which usually just unscrews from the filter manifold — for cleaning and backwashing. It should be as close as possible to the point of entry of the main water line before the hot water line branches off. Most homeowners put their whole-house water filter on a basement wall, but it can also go in the garage or in an outbuilding if that's more convenient (or if you don't have a basement). Note that it's very important that this unit shouldn't be installed outside.

A UV purification system is usually installed separately from the main filter, and it's easy to add. It typically mounts on the wall near a wall receptacle, and you connect the inlet port directly to the filter's outlet port. The UV outlet port in turn gets connected to the downstream shutoff valve.