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How to Choose a Water Filter

Learn about the different types of drinking water filters available, how they work, what they do,
and what you need to know about your water and plumbing before you start shopping

"Water is life". Maybe that's why we seem to take it so over-the-top serious sometimes: designer water from ancient, nigh-mystical sources, untouched by humans until placed in an elegantly conceived bottle. Yes, that is pure, life-giving, revitalizing water. Or is it? Maybe water is just water. Outside of taste, odor, and color, is there anything we can really judge water on without taking it to a lab?

It turns out there's no real health advantage to bottled water. It also turns out that it's regulated by the Food and Drug Administration as a food product, and not by the Environmental Protection Agency as...well, water. As such, there is no mandatory testing of the water being used, and quality standards differ. Ultimately, there's no way to guarantee that even the fanciest bottled water is any better than filtered tap water from a municipal supply. So if you're concerned about drinking high-quality water, you would be well-served to ditch the artesian springs of Norway and look to your own kitchen and the generally safe, treated water so regularly available to the majority of us in the United States.

While the quality of tap water in most American towns and cities is much higher overall than in many other areas of the world, you should be aware the water that reaches your tap can still be full of contaminants. Some are harmless, but undesirable - like suspended particles of silt, sediment, and sand (measured in turbidity) that make it cloudy and undrinkable, while others (like certain organic and inorganic chemicals and microorganisms) are responsible for any number of (sometimes dangerous) issues that are just plain scary. The type and severity of contaminants varies with every water supply.

If you're ready for pure, healthy water, the first step is to have your water tested. Filtration can be expensive, and you need to know exactly what you need to remove with your filtration system not only to save money, but to increase its efficiency and life. Check with your local water provider and health department for testing resources and recommendations. If your water comes from a well, we recommend testing the supply late in spring, when agricultural chemical runoff is at its greatest, to better gauge treatment.


Filter Design & Media

Spun water filter cartridgesSpun Filter Cartridges
Pleated water filter cartridgePleated Filter Cartridge

There are two primary types of filter design: pleated and spun (or wound). The latter simply have the filter media wound or spun around a base, creating layer after layer of filtration. Pleated filters have their media folded into a series of pleats, dramatically increasing the surface area available for filtration, and allowing for smaller housing sizes. In addition to the greater surface area, pleated filters have a lower pressure drop, increasing the flow rate out of the filter. In general, a spun filter is best if particles of a variety of sizes are to be filtered, thanks to their irregular and complex design. A pleated filter works best to block uniformly sized particles, and offers greater consistency in doing so since it is much easier to manufacture a pleated filter's pores to a specific size.

The pores of a filter are measured in microns. "Micron" is another term for the micrometer, or one-millionth of a meter (0.000039"). Probably the easiest thing to use as a frame of reference at this tiny scale would be a human hair: one strand is typically around 90 microns wide. The lower the micron rating, the smaller the filter's openings. Lead particles range from 0.1 to 0.7 microns, bacteria between 0.3 to 60 microns, and sand at anywhere between 75-150 microns.

Filters can be made of several materials; those that we offer are made of cellulose, polyester, polypropylene, or carbon. Cellulose filters are often the least expensive kind, and are derived from the very same cellulose that makes up the cell walls of plants and trees. Because of this organic component, these filters can be especially prone to bacterial infestations and "biofilm", where groups of microorganisms adhere to each other on the surface. This is why cellulose filters are not be used for untreated water, like that coming from a well. Cellulose filters will deteriorate if kept in a filter canister for too long which can cause the disintegrated particles to flow into your piping, leading to clogged aerators. Cellulose filters should be replaced after 3 months of continual use to prevent this type of disintegration and of course consumer aggravation.

Polyester and polypropylene are synthetic materials that are much more bacteria-resistant than cellulose. As such, they are a good option for untreated water supplies. These filters can be pleated or spun, and some can even be cleaned and reused for certain applications. With cellulose, polyester and polypropylene, it is mechanical filtration (filter physically traps particles) that does the work. As such, pay careful attention to the micron rating of these filters and the contaminants in your water, as that will be the sole determinant of the filter's success.

Activated carbon filter mediaActivated Carbon

Like the above materials, carbon filters not only provide mechanical filtration, but also have unique benefits that make them especially effective. Carbon is the go-to medium for taste and odor removal, and is particularly good at removing chlorine. Chlorine is used as a disinfectant in most municipal water supplies, and although the concentrations are monitored to be safe for consumption, there can be bothersome residual effects like odor and taste in your water, and drying-out of skin and hair. Chlorine also introduces Disinfection By-Products (DBPs), some of which can be harmful and even carcinogenic.

Chlorine molecules adhere to the filter surface (a phenomenon called adsorption), as do most DBPs. Adsorption provides greater efficiency than straight mechanical filtration, but once the carbon has been saturated, there is no possibility for re-use. And it's not just adsorption at work: some of the chlorine will be chemically reduced by the carbon, resulting in chloride, which presents problems only at high concentrations (and is easily removed by reverse osmosis).

In addition to chlorine, carbon can also be used to remove chloramine (another disinfectant used in municipal water supplies), but this requires significantly longer contact time between the water and carbon, as well as more carbon, to be successful. With carbon filters, the slower the flow rate, the more contact time contaminants have to diffuse and be adsorbed while inside the filter, so a faster flow is not necessarily best.

One of the major radioactive isotopes produced by nuclear fission, Iodine-131, can be removed with activated carbon (manufactured to have smaller pores), and most Giardia parasites are filtered out at 1 micron or less. Many of the Volatile Organic Compounds (VOCs), agricultural chemicals, and heavy metals regulated by the EPA can be addressed with activated carbon.

If you're having a problem with iron and rust, pour a glass of water and let it sit for 15-20 minutes. If nothing settles at the bottom, the particles are too fine and a filter will not help (you'll need to look into iron removal or a water softener). If particles do settle in the glass, however, a filter of 5 microns or less should take care of the problem.

The filter media you choose will be based on what you want to filter, and how well. Cellulose and synthetic filters are great for sediment, but offer little outside rote mechanical filtration. Carbon is your go-to for taste and odor concerns, as well as some VOCs, heavy metals, and biological contaminants.


Filter Units

We're all familiar with pitcher filters and faucet-mounted units. These products are convenient, efficient and effective in many standard applications. Most use carbon, taking care of many of the common contaminants found in domestic water supplies. But their efficacy is limited by their size and design, and filters must be changed often. The units we offer move beyond these, and into more heavy-duty filtration.

Countertop units share the convenience and ease of installation found in pitcher and faucet-mounted systems, but offer superior filtration. With more filter media available (usually carbon), more contaminants can be removed, and less filter changes need to be made. Because they only sit on your counter, removal and relocation is painless: these units can move with you, and are perfect for apartments and rentals.

An undercounter unit stays out of the way while providing even greater filtering power. Because they're installed under the sink, these units can be larger than their countertop brethren, with some housing multiple filters. Most UV and reverse osmosis units usually include their own faucet, so you'll need to make sure there's a spot for it in your sink or counter. Installation can be more involved, but is generally not outside the skill set of a handy homeowner.

For those particularly sensitive to chlorine or other contaminants, whole-house filters provide clean, safe water to every fixture in the home. Filtration at the main water supply prevents chlorine particles from being embedded in clothing, and from escaping into the air while dishwashing and showering, keeping them out of lungs and skin. Those concerned with chlorine absorption but not ready to commit to whole-house filtration have another option for preventing exposure in the shower: a point of use shower filter.

However, whole-house filtration also makes sense on another level: protecting your plumbing. Any sediment, chemical, or otherwise that isn't filtered out of your water travels with it through your pipes – all of them. Over time, depending on the nature and pervasiveness of the contaminants, pipes and fixtures can deteriorate prematurely, leading to all kinds of problems.

Speaking of sediment, it and sand have their very own dedicated filters! In areas where turbidity is especially severe, such specialized filters may be necessary. Sand separators are often recommended as the first stage in a filtering system, removing the largest of particles well before they have a chance to reach (and clog) a pre-filter or worse yet, a reverse osmosis membrane. This not only produces cleaner water, it improves the efficacy and lifetime of the other filters in the system, as well as your plumbing and fixtures.

Among our most popular units, the Lakos Twist II Clean Inline Water Filter offers key improvements over previous sediment removal products. Chief among these is the ease with which the unit is cleaned. Before, when a filter stopped performing adequately, a unit would need to be taken apart to varying degrees, introducing air into the line (potentially damaging pipes and pumps) and wearing out seals; it was a chore. With the Twist II Clean, nothing is opened or taken apart - the name says it all. With a quick and easy twist of the handle, water is made to flow backwards through the unit (backwashing), clearing waste off the filter in 20 seconds. The wastewater is expelled from a purge port at the bottom of the unit (we encourage you to find ways to give this water a purpose: irrigating your garden is a popular option). Filters are made of stainless steel, and come in several micron ratings to tailor the unit to your particular needs.

However, there are circumstances where a standard mechanical pleated filter may be better suited for your needs. When too many sediment particles are present in your water a larger surface area may be needed than the Twist II Clean can provide. If too many particles are present you could find yourself needing to purge it everyday. A larger pleated filter cartridge would allow you to go much longer in between cartridge cleanings.

For more intensive applications, we offer more powerful sand separators which utilize centrifugal separation to keep water clear. As water spirals inside these units, particles are thrown to the sides and bottom, collect in a chamber, and must be purged periodically. Since they don't use filters, all you need to worry about is purging the waste before it gets too backed up. Luckily for you, auto-purge systems are available that allow you to program the length of cleanings, and the interval at which they occur. Please note that centrifugal separators cannot remove mud, soil or red clay – these contaminants are too light to successfully separate from the water, and will only remain suspended in the liquid.

There are situations in which a standard mechanical filter, be it on top of or under your counter, does nothing for your water problems. And even if your whole house filter or sand separator leaves it looking clearer than ever, your water could be teeming with microorganisms. This is a particular concern for wells, which are not treated with chlorine or other disinfectants, nor are they subject to official regulation. Treated city water runs less of a risk, but a lot of things can happen between a water treatment facility and your tap. If you're at all concerned about your water, have it tested: this is the integral step in designing a system and selecting the proper filters. Should your water be home to biological contaminants – bacteria, viruses, molds, algae, parasites – you will need to move into the realm of reverse osmosis and ultraviolet light.

UV Filter Units

We can't see ultraviolet (UV) light – the wave frequency is just too high for our little eyes to discern. It's thanks to this high energy that UV is such a boon to water filtration. The electromagnetic energy is enough to penetrate the cell walls of most organisms present in water straight through to their DNA, "inactivating" them (that is, preventing reproduction). In fact, UV purification is recognized by the EPA as the "best available technology" for the inactivation of protozoan cysts like Giardia and Cryptosporidium.

However, UV systems require certain parameters be met to perform effectively:

  • Iron < 0.3 ppm (0.3 mg/L)
  • Manganese < 0.05 ppm (0.05 mg/L)
  • Hardness < 7 gpg
  • Tannins < 0.1 ppm (0.1 mg/L)
  • Turbidity < 1 NTU UV transmittance > 75%

If these levels are exceeded, scaling becomes a risk, decreasing the efficiency of the unit. Light becomes obscured, no longer powerful enough to inactivate. This is one of the reasons why pre-filters are always recommended. Without pre-filters UV systems do nothing to remove sediment or chemicals. By taking care of the things a UV unit by itself could not address, pre-filters allow the UV unit to perform at its greatest efficiency.

When looking for a UV unit, make sure it's sized correctly for your needs: know how many gallons of clean water your home requires daily, and the kind of flow rate you'll need to provide it. When in doubt, always go larger. Most manufacturers recommend the bulb be changed annually. We believe this is crucial: again, we cannot see UV light, so after a year a bulb may look as if it's perfectly fine while failing to emit enough UV rays at the right "dose". Keep up on bulb replacements and sleeve cleanings, and your UV unit will reward you every day.

Reverse Osmosis Filters

When you absolutely, positively have to filter every contaminant that you can, one option remains: a multi-stage reverse osmosis (RO) system. Like countertop and under-sink systems, RO is usually a point of use system. Unlike those, RO can filter out bacteria, viruses, and protozoa, along with pretty much everything else: heavy metals, VOCs, many radioactive isotopes, many minerals, and even some pharmaceuticals. Because of their effectiveness, these systems are always comprised of a pre-filter or three to ensure the RO membrane is not inundated by things that aren't worth its time. Pre-filtering also protects the membrane: chlorine, for instance, will damage it.

RO works by forcing water through a synthetic membrane with extremely small pores using water pressure and ionic diffusion. Water moves through the membrane just fine, but most everything else is blocked. RO systems require good water pressure going into the unit - at least 50psi - to function properly, and hard water folks beware: any harder than 10 gpg will require softening before entering an RO unit. And just in case these systems didn't sound picky enough, you shouldn't use copper pipe to transport any filtered water coming out of the system. An RO unit does not remove carbon dioxide from water, but does remove much of what it can react with. Left primarily with water, the CO2 will form carbonic acid, which in high enough concentrations can corrode pipe. Reverse osmosis removes dissolved solids to the point the water becomes almost too pure and this pure water then becomes aggressive and begins to dissolve any metal it then comes in contact with.

While RO is quite powerful, there are downsides. For one, it can take forever. Water is forced through the unit, but it's not with much force. The flow rates manufacturers specify are not to be trusted - you are more likely to win the Powerball jackpot than to get the advertised 50 gpd out of your unit. But for most households, that's just fine. The majority of families don't use more than around 5 gallons of drinking water a day, and with good pressure (>50psi), an RO unit rated at 30 gpd should meet those needs just fine. Most RO systems include a storage tank to work around this somewhat.

In addition to this lack of speed, there is the waste issue: RO wastes a lot of water. That is, up to 95% of water going into the unit will not reach your mouth. That's just the way it is. While it is possible to capture or reroute this wastewater, it's not something that's standard, and will require some thought and planning on your part. And the water that doesn't get wasted? Well, it's pure, but maybe a little too pure - RO filters out most minerals from water, including those that are beneficial to our health. World Health Organization studies of long-term use of RO filters for drinking/cooking water suggest that this could be hazardous to your health and remineralization of the water is recommended prior to being used for drinking or preparing food for health reasons as well as to improve taste.

To get the most out of your RO system, most manufacturers recommend that membranes be replaced within 2 years, but we prefer to suggest an annual change. Don't buy these ahead of time: membranes have a shelf life, and you'll want to guarantee you have the "freshest" replacement available. With new units, or just a new carbon pre-filter, it's a good idea to disconnect the membrane and run water through only the carbon for 5-10 minutes. Carbon filters will often "dump" some carbon into the filtered water when new, which is not good for the membrane.


Clearly, getting serious about filtration asks a lot of you. Though the choices and jargon may be intimidating, the water testing and monitoring laborious, it's important to be well-informed. Many of these high-quality water filter systems are not exactly cheap, and there's no point in wasting money on something that will actually do very little for your particular water. To know your water is to know what to target, saving money, time, and frustration. Your pitcher filter may be just fine for you... or you may need a multi-stage UV system. The only way to know is to find out. When you do, we're here to help.


Please note that any health-related statements made here are of a general and non-professional nature. The information is provided to help guide you in a purchasing decision, not a health issue. The products we offer are not intended to treat any medical condition. If you believe you may suffer from a sensitivity to chlorine or another contaminant, please consult with a medical professional, as well as a water treatment professional, to find the best treatment strategy.



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