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Most Popular Water Purification Technologies for Domestic Drinking Use

Point of Use Drinking Water Purification Technologies (FAQ)

* Specific questions from our customers (raw material)

* Activated Carbon (AC)

* Granulated Activated Carbon (GAC)

* Extruded Solid Carbon Block (CB)

* Powdered Activated Carbon (PAC)

* Reverse Osmosis (RO)

* Ultraviolet Radiation (UV)

* Ion Exchange (IEX)

* Distillation or Demineralization (DI)

*Absolute vs. Nominal Ratings

With so many choices of purifiers and filters on the market. Where do I start?

Start by reading about Doulton ceramic technology and various other technologies currently in use. This will familiarize you with the different technologies available to treat your water. Next, go to our Product Selector and follow the steps. Of course, you can always feel free to contact us ( We will make some recommendations to you based on your water supply and personal preferences.

Before purchasing a drinking water device determine which contaminants you want to remove, are these contaminants in your water, the degree of "purity" of the water etc. as there is no such a device or technology that "does all".

Which point of use (POU) technologies other than Doulton are currently used in domestic water filtrations?

The most popular and economical method is Activated Carbon (AC). Other technologies are Reverse Osmosis (RO), Ultraviolet Radiation (UV), Ion Exchange (IEX) and Distillation or Demineralization (DI).

Are there more effective technologies other than the above mentioned such as EPA certified?

First of all, technologies are based on their physical properties and scientific facts that can be easily understood. Second, EPA does not certify POU water treatment devices. In U.S. any device containing man made or natural "purifier" such as iodine, chlorine, silver or copper oxides, "food grade" pesticides etc. must register that device with EPA.

Stay clear of the products that you cannot understand how they work or use pseudo scientific (vague) terminologies such as; "pre coat technology", "FDA approved", "molecular sieving action", "redox technology", "alkalizer", "NASA technology", "EPA certified purifier", "patented" or other mysterious "technologies".

What are the certification standards and who sets those standards for POU filtration devices?

The certification standards vary from region to region and some parts of the world don't have any. The certification standards are set by governmental institutions, industries associations and or combination of both. For example ISO (International Standard Organization, Zurich, Switzerland) sets world standards in manufacturing procedures (toughest to achieve and maintain), while in U.S., ANSI (American National Standard Institute) set standards. For example: In US for food equipment and POU devices NSF in collaboration with ANSI write standards that will meet EPA and FDA guidelines. NSF standards for POU filtration devices are 42, aesthetic contaminants (chlorine reduction) and 53, health related contaminants (cysts and turbidity reduction).

What is the difference between "tested by NSF" filter and a filter "tested to NSF standard"?

None. One was tested by NSF laboratory or their subcontract labs while the second one opted for less expensive ANSI accredited laboratory e.g. Underwriter Laboratories etc. One have to keep in mind that all those tests cost thousands of dollars.

Which POU technology remove most contaminants out of the water?

"Contaminants" is a very general term which determines the use of treated water. For everyday drinking and cooking water a well designed activated carbon block is best in removing chlorine and it's by-products, pesticides, herbicides, carbon based industrial chemicals as well organic pharmaceuticals. In addition to good carbon block incorporates ion exchange media to remove heavy metals such as lead. Carbon block does not remove "contaminants" such as calcium, magnesium, potassium and other natural minerals which contributes to fresh, spring like thirst quencher.

A well designed and maintained distiller, laboratory grade* RO systems maintained and periodically tested by a qualified technician using high quality pre-treated water (*not to be confused with inexpensive domestic RO systems commonly sold in big box stores or by softeners salesman).

I am specifically concerned about removing parasitic cysts like cryptosporidium and giardia from my water. What is the best filtration or purification method for cysts?

Generally cysts size in range from about 3-7 microns and can be reduced by fine filters however to completely remove 100% a filter pore size have to be at least 1 micron absolute with greater than 99.99% efficiency. Many filters on the market claim cysts reduction using surrogates (AC fine test dust in 0.5-3 micron size range) test standards vs. live cysts method which is tougher and more accurate test.

For immune compromised individuals the following POU labeled devices may or may not remove Cryptosporidium.

POU device labeled only with these words may not be designed to remove Crypto POU device labeled with these words indicate should be able to remove Crypto
  • Pore size of 1 micron or 1/2-micron filter
  • Effective against Giardia
  • Effective against parasites
  • Carbon filter, water purifier or softener
  • EPA approved - EPA does not approve or test filters
  • EPA registered - EPA does not register filters for Crypto removal
  • Activated carbon, removes chlorine
  • Ultraviolet light or UV purifier
  • Reverse-osmosis (without NSF testing)
  • Pentoidine resins, bacteriostatic
  • Reverse-osmosis tested to ANSI/NSF 53 for cyst removal, ask for results
  • Absolute pore size of 1 micron or smaller (w/>99.99% efficiency 4 log test standard protocol), ask for results
  • Distiller
  • Tested with live crypto cyst and certified to NSF Standard 53 for cyst removal, ask for results

NOTE: There is general misconception even among medical professionals recommending reverse-osmosis not understanding operational and maintenance requirements of such POU device to be able to remove Crypto.

Most all carbon filters are in particulate reduction range.

Distillers and RO manufacturers often "claim" that natural minerals in water are not beneficial for you while POU manufacturers "claim" the opposite. Who's right?

Our view is that we should rely on minerals through food intake rather than water. On the other hand have you ever tried "pure" water? It's flat and lifeless, taste stale and is very acidic. Laboratory water should be "pure". Drinking water should be safe and wholesome, free from pathogenic bacteria and chemicals, full of oxygen and mineral content that gives water spring-like taste and freshness. Should you opt for "pure" drinking water then distilled water is much "purer" than reverse osmosis water even under best RO performance conditions.

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Reverse Osmosis (RO)-FAQ

Reverse osmosis (RO) is a membrane filtration process separating dissolved salts from a water stream. In RO, not only are insoluble particles rejected by the membrane but also molecules and ions in solution. Concentration of ions near the membrane sets up ‘polarization’ phenomena which results in an increase in the osmotic pressure of the solution to be treated, sometimes followed by precipitation.  The continuing flow of input water under high pressure (>200 psi) flushes the membrane, which removes the ion concentrations and/or precipitates.
RO systems are not normally "water efficient" and wastewater rejected by the system may be significant. Purchase and installation costs can be significant. RO membrane are notoriously prone to scale and bacterial build-ups and ruptures. Slime-forming bacteria can cause rapid deterioration of performance. If you own a Doulton filter you'll know what "slime-forming bacteria" is. When you clean the ceramic candle it is the pinkish slippery bio-film that built up on the surface slowing your filter flow rate.

Due to various factor that can affect membrane performance a major membrane manufacturer have the following statement in red letters imprinted on the packaging: "Do not rely on this membrane for Cryptosporidium or Giardia cyst removal".

High end laboratory RO systems rejects high degree of organic and inorganic compounds producing high quality pharmaceutical grade water. To achieve this producers pre-treat the water using various pre-treatment methods such as passing through pre-filters, ion exchange resin beds etc. Under right pressure (>200 psi.) and temperature the pre-treated water is then pumped through two RO membranes connected in series (double pass) rejecting dissolved compounds in molecular and ionic state. These systems are constantly maintained and monitored by trained personnel using sophisticated equipment.

RO water lacks minerals and oxygen, hence the "flat", "stale" taste when used for drinking.

In all cases, a Doulton ceramic pre-filter will prevent membrane bacterial fouling. RO plants producing potable water often use Doulton ceramics as a final polish filters (physical barrier).

Distillation- FAQ

Distillation or demineralization is usually an effective method of preparing safe drinking water. However, carry-over's of volatile organic compounds (herbicides and/or pesticides) may be an issue since they may be evaporated and re-condensed with the water.

Like RO, distilled water is very acidic and should be stored in glass container in order to prevent leaching (recontamination). Since is virtually dematerialized it is often called "starving", "thirsty" or "hungry" water. Like RO, distilled water lacks minerals and oxygen, hence the "flat", "stale" taste when used for drinking. Distilled water is mainly used for industrial processes such as electronic circuit boards etching and rinsing, photographic's and other applications.

In most cases, pre-filtration, including a ceramic filter element, will improve the effectiveness of a distillation system by improving the quality of supply water.

Ultraviolet Radiation UV-FAQ

Ultraviolet systems (UV) expose supply water to intense ultraviolet radiation, which kill pathogenic bacteria (cholera, typhoid, salmonella, dysenteriae, etc.), virus however is not effective against cysts.

Since UV is not a physical filter, suspended particles (or turbidity) in the water could “shade” bacteria from the direct rays from the UV source “live” bacteria and virus could pass through the system. For this reason a good UV systems have ceramic cartridge as a pre and final filter. The following factors can reduce the UV performance:

  • Iron and hardness, which build up on the quartz sleeve is a process industry known as "fouling".
  • Iron, decayed organic matters, tannins and any UV energy absorptive material commonly found in tap water.

If you own a UV without Doulton ceramic pre-filter and rely on it for microbiological protection make sure to clean the quartz sleeve often and change the UV bulb once a year.

UV, by itself, does not remove any particulate matter or turbidity. It does not remove volatile organic compounds such as pesticides or insecticides. Purchase, installation, operating and maintenance costs should be considered before selecting UV as a drinking water treatment system.

UV manufacturers performance claim is based on 1 or less than 1 NTU* turbid water.

* Turbidity refers to the concentration of un dissolved, suspended particles present in a liquid measured in
Nephelometric Turbidity Units (NTU). It is important to note that turbidity is a measure of sample clarity and not colour. Water with cloudy or opaque appearance will have high turbidity, while water that is clear or translucent will have low turbidity. High turbidity value is caused by particles such as silt, clay, microorganisms, and organic matter. By definition, turbidity is not a direct measure of these particles but rather a measure of how these particles scatter light.

Turbidity is a very complex analytical measurement which can be affected by many factors. Some are inherent in the instrument’s design such as angle of detection, light beam aperture, incident beam wavelength and colour sensitivity of the photocell. However, there are other factors such as stray light, air bubbles and care of vial, which can be prevented through proper care of equipment and accessories.

Ion Exchange IEX- FAQ

Most popular Ion exchange (IEX) media in POU for heavy metals reduction is ATS or ATC media, zeolite etc. Various IEX resins are often used for industrial processes for specific water use. Ion exchange theory in layman language is simply gaining and loosing atoms (swapping atoms). In drinking water for example soluble lead is a positive ion whilst chlorine is a negative ion (cat ions+, anions-). Most common ion exchange in rural area (well water) is "Softener".

An other popular often called "emerging technology" or "redox technology" etc. is IEX media used in POU is KDF 55 (copper zinc alloy in granule form) for it's high chlorine reduction. By simply swapping atoms this metal alloy turns chlorine into harmless chloride.

Many POU "makers" using this alloy claim soluble lead reduction, bacteriostatic proprieties, some go as far as cysts and bacteria removal and a host of other "miracles". We simply don't know what does it do with the lead, does it convert it to a particulate lead or what pH operating water conditions must be used? Under what condition is bacteriostatic?. If you plan on buying a POU using KDF media, do your investigating as to performance claims. KDF 55 is widely use for shower and garden filters which are impressively compact and effective de-chlorinator.


There is a range of water purification products on the market and there is Doulton. Effective and cost efficient drinking water treatment technology.

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