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Project Difficulty:
Difficult
Estimated
Project Time: 3 to 6 hours
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| Tools and Materials: |
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Reverse-osmosis water filter kit
Self-piercing inlet saddle valve
Saddle drain clamp
Drain shutoff valve
Power drill and bits appropriate for your installation
Pencil
Flashlight
Extension cord
1/4" plastic tubing, as needed
Utility knife (to cut plastic tubing)
Center punch
Hammer
Screwdrivers
Pliers
Adjustable wrenches
Basin wrench, as needed
Filter wrench, as needed
Liquid household bleach
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Teflon tape, as needed
Plastic anchors
Screws
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Why Install a Reverse-Osmosis Water Filter?
Today, people are increasingly concerned about the quality of the water that they consume. Under the best of conditions, it's possible that water may contain hazardous contaminants, ranging from dissolved organic and inorganic materials, to suspended particles and microorganisms. If you live in a home with older pipes, you may also be exposed to lead in your water. Even the chemicals, like chlorine and fluoride, that many municipalities add to water to kill bacteria or to fight tooth decay may be harmful to humans. If such chemicals are not used, your water could be harboring deadly parasites. If you suspect your water may contain microorganisms, lead, or other contaminants, have your water tested.
To decrease their exposure to possible contaminants, many people drink and cook with bottled water or put distillers or disposable cartridge filters on their water supply lines and faucets. However, bottled water may not be any purer than the water taken from your faucet, distilled water requires boiling and tastes flat, and although charcoal filters improve the taste and remove odors from water, they do little to remove chemical contaminants and microorganisms. If you find your water is contaminated, choose the correct water filtration system to correct the problem.
Reverse osmosis (RO) is generally recognized as the best system for purifying water while retaining good taste. The EPA recommends reverse osmosis filters for microbiologically safe water. Yet, an RO system alone will still allow certain waterborne germs to pass through. To knock out these types of contaminates, most RO systems incorporate some additional type of filtering, usually a replaceable carbon post filter.
What Is Reverse Osmosis?
Reverse osmosis involves the passage of potable water through a semi-permeable membrane. In a normal osmotic reaction, water containing a dissolved substance in low concentration will flow through a membrane to the side containing a higher concentration of the dissolved substance. If pressure is applied to the side having the higher concentration of solution, the flow of water can be stopped or even reversed. When the flow is reversed, this is called "reverse osmosis." In this case, it is the water that has less dissolved substance that is desirable; this is the purified water.
How Do Reverse-Osmosis Systems Work?
The reverse-osmosis water filter is usually installed beneath your kitchen counter. The filter commonly consists of five components: one or two sediment pre-filters, the RO membrane filter, a drain for reject water, a small treated water storage tank, and a carbon post-filter. In addition, an air gap is built into the faucet; this serves as a sanitary device by preventing wastewater from flowing back into the filter. (Fig. 1)
Most reverse-osmosis systems purify water in 3 to 5 phases. The early phases use pre-filters to remove particles of dirt and sediment, chemical contaminants, certain microorganisms, and odors; a middle phase employs the RO membrane itself to eliminate dissolved solids, metals, and other microorganisms; and a final phase actuates a carbon (charcoal) post-filter to eradicate any remaining traces of chemicals and odors, thereby improving the quality and taste of the water.
How Much Purified Water Can a Reverse-Osmosis System Produce?
Reverse-osmosis systems are rated by the number of gallons of filtered water that they can produce in one day. However, this rating system can be somewhat misleading. A system that is rated for 5 gallons per day, for example, may take several hours to produce a single gallon. If the neighborhood kids all come in for iced tea, the filter may not be able to keep up. What you really want is a filter with a higher rating, which means that it will have a faster recovery time as the treated water becomes depleted.
Because even the fastest filter cannot produce filtered water on demand, RO systems typically include a pressurized storage tank which serves as a reservoir for a supply of filtered water. These tanks, which usually have a 2- to 5-gallon capacity, are typically equipped with a shutoff valve that allows you to change filters easily without having to drain the storage tank. There should also be an automatic drain shutoff valve that shuts off the drain water when the water pressure in the storage tank reaches 80 percent of the pressure in the drain line. Without it, the system would run continuously, wasting a tremendous amount of water in the process. Even with an automatic drain shut off valve, an RO system is not particularly conservative of water. Typically, for each gallon of water filtered, two gallons or so are drained as "reject water" (brine).
Installing a Reverse-Osmosis System
When installing a reverse-osmosis system, be sure to follow manufacturer's instructions carefully. Directions may differ significantly between products. Below are guidelines that may help you to understand what might be involved, but may not exactly match those for the system you choose.
Although most RO units are installed beneath a sink, you may want to consider alternate locations that will leave your kitchen cabinet space free. Install the unit where it will not be subjected to freezing, including crawl spaces and basements. Wherever you decide to put it, the water filter should be accessible for filter replacement. You should also consider accessibility to optional outlets, such as a second faucet or icemaker.
Before purchasing a reverse-osmosis system, measure the space where you will install it; be certain that the filter unit and the accompanying storage tank will fit. Some systems have a storage tank with a removable base, giving you the flexibility of being able to install the tank either vertically or horizontally.
Also check where you will place the faucet. Ideally, you should use an accessory hole if your sink has one. Another option is to remove the spray hose and use that hole. As a last resort, you will have to drill a hole in the sink or counter.
For your reference, fhe following are general guidelines for installing a RO system under a kitchen sink.
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1.
Prepare to Install the Under-Sink RO System
Empty your sink base cabinet, and then turn off the valves to your water supply risers. If there are no valves under your sink, then shut off the house water main, which is usually located in the basement. Open your kitchen faucet to relieve any pressure in the line.
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2.
Install the Water-Supply Valve
To supply your filter with water, you must tap into the cold water line serving the sink. You can do this in one of two ways; either with a self-piercing inlet saddle valve (Fig. 2) or with a dual stop valve. If you install a self-piercing saddle valve, don't pierce the piping at this point. If you choose to install a dual stop valve, use this to replace your existing cold water shutoff valve. The dual stop valve is a valve with two 3/8-inch exit ports, one for your faucet and another for an alternate device, in this case the RO filter. Neither the saddle nor the dual stop valves require soldering.
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3.
Connect the Saddle Drain Clamp
Provide a drain connection using a saddle drain clamp or tee. Position the saddle drain clamp as high up on the drain line above the P-trap as feasible, but away from the dishwasher or waste-disposal drains, if there are any (Fig. 3). Drill a 1/4- to 3/8-inch hole in the pipe. Attach the clamp to the drain line, properly positioned on the drill hole. Depending on the manufacturer, 1/4-inch plastic tubing may or may not come with your filter unit. In either case, insert the tubing into the opening of the saddle drain clamp, using the fasteners included with your system to secure and seal the tubing.
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4.
Locating the Faucet
The pure water faucet can be located on your kitchen sink or countertop. Make sure the water from the faucet will fall into the sink basin. If your sink already has an accessory hole, you can remove the cap and position the pure water faucet there. Or, detach your spray hose and use the spray hose hole. If you cannot use either of these methods, then you will have to drill a new hole in the sink or countertop. Check above and below the sink or countertop for proper clearance before drilling. Be sure there are no obstructions.
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5.
Drill the Faucet Hole (If Needed)
If you do not have a faucet hole available, you'll have to drill one. If your sink is stainless steel, then center-punch a pilot hole where you want to install the faucet. Use a 1/2-inch standard twist bit to drill the final hole in the metal. A standard twist drill bit will also work on solid-core countertops, but a simple wood-drilling bit will suffice for a laminated countertop, and a carbide-tipped bit is what you must have for drilling through ceramic tile.
Drilling through a porcelain and cast-iron sink requires special hole saws and bits. Unless you are familiar with the procedure, consider having a professional install the faucet, to avoid any possible mishaps.
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6.
Mount the Faucet
Fasten the faucet to the precut hole, in accordance with the manufacturer's requirements (Fig. 4).
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7.
Anchor the Filter Housings
The housings for the pre-filter cartridges can either sit on the floor of the sink cabinet or be suspended by a bracket screwed to the cabinet wall (recommended). Be sure to provide easy access and enough attached tubing so that the filter housing can be conveniently removed for cartridge replacement.
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8.
Install the Carbon Post Filter and RO Membrane Filter
When installing the filters and connections, follow the manufacturer's instructions carefully. In general, attach the carbon post filter to the top of the RO membrane filter. Some systems may allow you, instead, to hang the carbon post filter a few inches below the faucet, if this is preferred. Connect the tubing between the filters (including prefilters) and the faucet.
Insert the drain flow restrictor into the fitting of the RO membrane filter. This device uses capillary action to control the rate at which reject water exits the system, also allowing just enough water to rinse the RO membrane. Furthermore, it provides the necessary back-pressure on water at the to force the water through the RO membrane and into the pure water storage tank. Connect the tubing from the drain flow restrictor to the drain.
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9.
Make Optional Connections
Depending on your needs, you may opt to connect your RO membrane filter system to a second faucet, a refrigerator cold water tap, or an icemaker. You can do this by adding a compression tee just before each additional fixture.
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10.
Connect the Tank and Water Lines
Following manufacturer's instructions, assemble the tank components. Then use tubing to connect the "OUT" side of the filter unit to the water storage tank. Lastly, connect tubing between the inlet saddle valve and the "IN" side of the filter unit.
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11.
Turn on the Water
Open the valve on the water storage tank. Turn the water back on.
If you've installed a self-piercing inlet saddle valve, turn it clockwise; this will pierce the inlet pipe or tubing. Turn the valve counter-clockwise to retract the spike and allow the water to flow.
Carefully check the assembly for leaks, and then fill the tank.
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12.
Disinfect the Water Storage Tank
Your water storage tank may have picked up minor impurities during manufacture. It may require decontimination before use. Follow manufacturer's instructions on how to do this. Recommendations may indicate you should do this before setup is complete, or when everything is connected.
Usually, disinfecting the tank would involve pouring a solution of liquid household bleach into the system, filtering it through the system, letting it set a while in the tank, and flushing the system out. Do not use the first reservoir of water--dispense it into the drain.
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