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Frequently Asked Question


What is Reverse Osmosis?

This water purification process has gained in popularity over the last 20 years since it was first used commercially in 1968. It is used extensively for purifying sea water and uses membrane (a thin film or skin through which water molecules can pass) technology.

The easiest way to explain reverse osmosis is by firstly explaining osmosis.

Osmosis is the movement of a low concentration solution through a semi-permeable membrane into a high concentration solution such as seawater or contaminated water.

In reverse osmosis, the idea is to use the membrane to act like an extremely fine filter to create drinking water from contaminated water. The pressure is applied to the contaminated water, reversing the osmotic process and forcing water molecules through the membrane.

Reverse osmosis membranes don’t allow particles or molecules larger than 0.0005 microns to pass through to the other side of the membrane. Essentially only water (H20) passes through while other contaminants, bacteria, viruses, chemicals and other dissolved substances are flushed to drain.

As a size comparison against 0.0005 microns; a human hair is 100 microns, the smallest particle visible to the human eye is 50 microns, the smallest bacteria is 0.2 microns and the smallest virus is 0.002 microns.

Reverse Osmosis membranes are manufactured with different pore sizes and support structures and from different materials. Membrane pore sizes can vary from 0.0001 microns to 5 microns depending upon the type and purpose.

Seawater or Desalt membranes are constructed to operate at very high pressures up to 7,000 kpa with small pores that reject in excess of 99% of salt at loading greater than 32,000 mg/l.

Brackish/Salt contaminated water membranes operate at high pressures around 1,500 kpa and have larger pores to reject in excess of 99% of salt at loadings greater than 2,000 mg/l.

Lower pressure/low energy membranes are designed to operate between 400 and 1500 kpa with more open larger pores designed to reject 99% of salt at loading around 500 mg/l for groundwater and municipal supplies.

There are two main types of reverse osmosis membranes commonly used in home reverse osmosis filter systems:

  • Thin Film Composite (TFC)

  • Cellulose Triacetate (CTA)

TFC membranes have considerably higher rejection rates, and filter out more contaminants than CTA membranes. However, they are more susceptible to degradation by chlorine and other oxidants and need to be protected from them by pre-filters.

TFC Membranes

These membranes are made by forming a thin, dense contaminant rejecting surface film on top of a porous substructure. The materials of construction and the manufacturing process for these two layers can be different and altered for the desired combination of pure water produced versus contaminants rejected. The pure water production and contaminant rejection characteristics are predominantly determined by the thin surface layer which thickness ranges from 0.01 to 0.1 micrometers.

Several types of TFC membranes have been developed including aromatic polyamide, alkyl-aryl poly urea/polyimide and polyfurane cyanurate. Polyimide membranes are highly susceptible to degradation by oxidants such as chlorine and chloramine. These must be removed to prevent damage and destruction of the membrane.

CTA Membranes

These membranes were developed along with the first reverse osmosis systems in the late 1950’s. They are composed of a thin dense surface layer (0.2 to 0.5 micrometres) and a thick porous sub-structure. Contaminant rejection is undertaken by the thin dense layer with the sub-structure providing structural support. They are relatively inexpensive to manufacture and hence are cheaper to buy than TFC membranes.

CTA membranes also have a low rejection of organic contaminants, low pH tolerance but a high tolerance to oxidants such as chlorine.

The chemical 1,4 dioxin is used to create the membrane porosity features. This chemical causes cancer with some traces of it left after manufacturer requiring considerable flushing before use.

Contaminant Removal

The removal of inorganic contaminants by reverse osmosis membranes is complex and is dependent upon the interactions and mixture of irons in the feed water. Ionic contaminants are more readily rejected than neutral ones and polyvalent ions are rejected to a greater extent the monovalent ions. If the polyvalent ion is strongly hydrated, rejection is even higher.

As electrical neutrality must be preserved, ions diffuse across the membrane as a cation-anion pair. As a consequence, rejection of a particular ion depends on the rejection of its counter ion. An example of this is with sodium; sodium sulfate has a higher rejection than sodium chloride because the divalent sulfate ion is rejected to a greater extent than the monovalent chloride ion.

pH variations also affect the rejection characteristics of the membrane depending upon membrane composition and ion type. For example, fluoride rejection increases from 45% to over 90% as pH increases from 5.2 and 7.2 whereas nitrate rejection decreases slightly as pH increases from 5.2 to 7.0.

A large number of councils are now using chloramine to treat drinking water supplies instead of chlorine. This chloramine contains ammonium ions which are poorly removed by activated carbon causing dramatically reduced rejection rates and degradation of the membrane. The variability of local water conditions and sources also varies the performance of the membrane although a Total Dissolved Solids (TDS) monitor will show the current performance of the unit. Specific ion rejection performance can however only be determined by selected testing. As a general guide reverse osmosis membranes are more effective in rejecting ions or organic solubles with molecular weights greater than 200 however carbon filters before and after the membrane can greatly affect the contaminants rejected or absorbed thereby affecting the overall performance of the system. The larger the pre-carbon filter ie 12” in the Aqua Safe ASRO4 unit the greater the chloramine and contaminant removal.

While membranes are successful at removing bacteria and viruses the systems can be contaminated from the product water side colonizing the tape tubes and storage tank. Regular disinfection (every 6-12 months) is necessary to maintain the water quality. This can generally be done by the system owners at very low expense or carried out by service technicians.

    How many types of water purifier there in the market?
    Before buying the water purifier u mush know what all the type of water purifier there in the market.

    How many types of water purifier there in the market?
    • UV purifier
    • Ro purifier
    • RO + UV purifier
    • UF purifier
    • Ro + UV+ UF +TDS technology purifier

    What is UV purifier?
    Ultraviolet purifier is which kills the micro bacteria in the water. And self as good as boiled water.

    What is Ro purifier?
    Reverse osmosis (RO) is a water purification technology that uses a semi permeable membrane. This membrane-technology is not properly a filtration method. In RO, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by chemical potential, a thermodynamic parameter. RO can remove many types of molecules and ions from solutions and is used in both industrial processes and in producing potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be “selective,” this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as the solvent) to pass freely.

    If it’s municipal water (Cauvery water which is being supplied by BWSSB)
    U can buy the UV and Carbon model water purifier whereas in municipal water u gets only sedimentation and little amount of micro bacterial. But in this purifier, the taste water will be the same.

    If it’s well water, bore well water or lake water (tanker water)
    Her u cannot buy a UV are Carbon model water purifier because her the TDS (Total Dissolved Solids) of water will be HIGHER than the municipal water .U has to go for the RO model water purifier. Her u gets the taste of the water.

    What is TDS?
    Total Dissolved Solids (TDS) are the total amount of mobile charged ions, including minerals, salts or metals dissolved in a given volume of water, expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm). TDS is directly related to the purity of water and the quality of water purification systems and affects everything that consumes, lives in, or uses water, whether organic or inorganic, whether for better or for worse.

    Did You Know?
    Different government agencies have different requirements for water quality.
    • The U.S. EPA sets the maximum contaminant level for TDS at 500 ppm.
    • The World Health Organization (WHO) sets the maximum contaminant level for TDS at 1000ppm. (parts per million)

    What is the maintenance should be done after buying a water purifier?
    • U has to Service your purifier ever periodical time. (3 or 6month)
    • And change of filters every one year.
    • If it’s UV model purifier u need to change UV lamb every two years.
    • If it’s a RO model purifier u need to change RO membrane every two years.

    Comparison List

    Type of filter

    Contaminants removed

    Price (Rs)

    Power required

    Installation Cost (Rs)

    Replacement of filters

    Bacteria & viruses


    Heavy metals

    Time period

    Cost (Rs)

    Activated carbon







    3 months to 1 year









    6 months to 1 year; UV lamp will only need replacement if it is fused

    250-350 (filters) 500 (UV lamp)

    Reverse osmosis







    6 months to 1 year; 1-3 years for RO membrane

    400-450 (filters) Up to 2,500 (membrane)

    Installation costs may vary

    Anti-Scaling Balls
    • Water anti-scale product polyphosphate siphons balls.
    • Domestic drinking water treatment safety.
    • Remove scale and corrosion.



    Chemical Auxiliary Agent



    Polyphosphate glassy ball glassy transparent ball




    Anti-scale polyphosphate glassy ball -siliphos balls Application
    1. Protect water systems in hotels, public buildings, private households and industry against scale formation and corrosion.
    2. Prevents “brown” or “red” water and clogged pipes
    3. Keeps pipework clear
    4. keeps maintains cost down, saves expensive repairs or even replacement of water pipes, boilers, heaters, cooling systems etc.
    5. Widely used for whole-house pre-filters, pure water filters etc.


Hard water is water that has high mineral content. In domestic settings, hard water is often indicated by a lack of suds formation when soap is agitated in water, and by the formation of limescale in kettles

Water hardness is created by high levels of calcium and magnesium ions in the water although other cations such as strontium, iron manganese and barium can also contribute. Hard water requires more soap than soft water to obtain lather or soapy bubbles. It can also cause the scale to form on hot water appliances, air conditioners, etc.

What are the Effects of hard water?

Skin and hair are affected by hard water. Hard water also forms deposits that clog plumbing Hard water can cause the scale to build up on water heaters and pipes, limiting the water flow, reducing the life of the product and increasing operating costs and maintenance on water-using appliances. For example, water heaters last up to 50% longer and consume up to 29% less energy


Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water is more compatible with soap and extends the lifetime of plumbing. Water softening is usually achieved using lime softening or ion-exchange resins

Advantages of Using a Water Softener

Prevents Hard Water Scale

Prevents Staining on Bathroom & Kitchen Fixtures as well as Dishes, Dishwasher, Washing Machine and Clothes

Significantly Reduces Soap and Cleaning Product Consumption

Provides Excellent Grooming & Cosmetic Benefits

Reduces Water Heating Costs

Prolongs the Life of Water Heaters, Icemakers, Dishwashers, Coffeemakers and Plumbing Fixtures

Other Benefits Include…

  • Improved taste of water, tea and coffee and keeps your kettle/jug clean.

  • Helps keep bath tap and shower walls clean with less scrubbing.

  • Water saturates and cleans better, gives whiter softer clothes with less detergent.

  • Dishwashers and washing machines remain clean and scale-free requiring less maintenance.

  • Stops scaling in piping removes existing scale, improves water pressure.

  • Lawns and gardens require less water to stay green and healthy.

  • Less water spotting on windows and buildings.

  • Protects water heaters from corrosion, adding years to their life.

  • Reduces salt build-up and encrustation on air conditioners.

Beneficial for…

  • Residential and commercial uses.

  • Swimming pools.

  • Motor homes and boats.

  • Golf courses and irrigation systems.


Most water softeners on the market operate on an “ion exchange” system. This is where hardness ions (calcium and magnesium) are exchanged for sodium (salt) or potassium (salt) ions. This takes place within the resin tank of the water softener. When water flows through the tank it comes in contact with small resin beads that are covered with sodium or potassium ions. As the water flows through the resin beads, the calcium and magnesium ions trade places with the sodium ions. That is why softened water becomes higher in salt content.

Eventually, as larger volumes of water are softened the beads become exhausted and contain nothing but calcium and magnesium, thus requiring recharge [Regeneration]. A water softener is the most common ion-exchange softener being sold locally. This system meters the water usage over time and only regenerates when needed. Some softeners operate on a timer or schedule that regenerates at set increments. This older technology can be very wasteful in terms of salt and water usage as the softener will regenerate even if it is not required due to low consumption in the home over a given time period. At the same time, these models could leave you short of soft water if you have higher consumption due to house guests

WHAT IS Regeneration?

The process of washing the resin in a concentrated solution of brine is called regeneration


There are generally three different types of water softener salts available.


  • SOLAR SALT ( Salt produced by the evaporation of seawater )

  • EXAPORATED SALT ( Refined and completely purified salt, such as table salt )

Rock salt is cheaper than solar salt or evaporated salts but contains more insoluble material; as a result solar and evaporated salts keep your water softener cleaner. The type of salt you choose to buy depends on the frequency of regeneration. If your water softener regenerates a lot you will experience quicker. so u have to use the rock salt. However, for the average homeowner, this will not be a concern as the excess material is washed away during regeneration

How often the Regeneration of water softener should be done?

In most cases, water softeners can be regenerated once per week. This of course depends on your water quality, and how hard your water is. For harder water, you may find yourself changing once every five days, for softer water you may only have to change once every two weeks.

Ultra Violet Filtration

UV System Advantages

  • No toxic by-products produced.

  • Cannot overdose the treated water.

  • Treatment is not sensitive to temperature and pH differences.

  • Has no smell or taste residual.

  • Requires very little contact time (seconds) versus minutes for chemical disinfection.

  • Simple installation, a small amount of space required.

  • Low running and maintenance costs.

  • Does not affect minerals in the water.

UV System Disadvantages

  • Not suitable for water with high levels of suspended solids, turbidity, colour or soluble organic matter.

  • Unit performance is affected by microbial loading and chemical characteristics such as nitrites, sulfites, iron and hardness levels.

  • No disinfection residual ie no free chlorine.

Typical UV Systems Include:

  • A stainless steel treatment chamber.

  • An inlet and outlet.

  • A quartz lens and lamp.

  • An electrical connection containing a transformer, a UV lamp fail alarm and other components.

Other options may include:

  • Inbuilt surge protection or voltage regulator.

  • Treatment chamber made from poly for use in corrosive environments.

  • Multiple UV lamps in the one chamber

  • Mechanical wipers to clean the quartz lens; either manual or automatic.

  • Sensors to monitor the UV intensity connected to alarms.

  • Lamp shut down when no flow is registered for a period of time.

  • Telemetry systems for remote monitoring.

Unit Selection

The size of the model of the UV system required depends upon 3 main factors:

  1. The water quality to be treated.

  2. The flow rate or quantity of water to be treated.

  3. The features or options required or selected.

Once this information is known or determined a particular model or number of suitable models can be selected and quoted.


Although the maintenance requirement is low the units UV chamber and quartz lens do need to be inspected and cleaned every 6-12 months. The lamp should also be replaced, o-rings lubricated valves, switches and sensors checked and tested.

Water Filtration Facts

Micron – is a unit of measure used to describe the level of filtration provided by a water filter. How fine the filter is, what the size is of the smallest particle it removes. A micron is a thousandth of a millimetre i.e. 0.001 mm = 1 micron. For example, a 20-micron filter removes particles down to 0.02 mm.

To put this into perspective a human hair is 100 microns, the smallest bacteria is 0.2 microns, the smallest virus is 0.002 microns, most high quality Reverse Osmosis Systems filter down to 0.0005 microns and the human eye can see particles down to 50 microns.

NSF Filter Certification

NSF (National Sanitation Foundation) International is an independent organisation, founded in 1944, set up for testing products that affect water quality and food safety. The organisation has offices around the world with a head office in Michigan USA. NSF is recognised as a leading world authority in the development of standards and testing of water filtration products. These comprehensive standards provide the basis by which product manufacturers can demonstrate the quality, reliability and performance of their products, and through which buyers and consumers can be assured of their safety and benefits. If products pass testing procedures they are certified and can then use the NSF logo and mark.

Why is NSF Certification Important?

Consumers buy water treatment systems for any number of reasons. Maybe they are looking for a system that will reduce unpleasant taste, odour or discolouration in their water, or perhaps they need a system that can reduce harmful contaminants, like lead or microbiological cysts.

NSF has developed standards, certification and testing programs in order to give assurance that the system will do what the manufacturer/supply claims it will do.

NSF certification guarantees (through testing) that:

  • The system is able to reduce the contaminants claimed by the manufacturer;

  • The system is structurally sound and it doesn’t add harmful substances to the water;

  • Advertising, product literature and product labelling do not contain false or misleading information;

  • The production facility undergoes annual unannounced inspections by NSF and each model is periodically retested.

Each NSF standard is technology or system-specific i.e. Cartridge filter systems have a different standard to Reverse Osmosis Systems and Shower Filter Systems.
Following are the standards applicable to each type of system and technology.

Product Type

Contaminant Reduction Claims


Carbon, ceramic or other filter system

Aesthetic – chlorine reduction particulate reduction, chloramines reduction, etc.


Carbon, ceramic, or other filter system

Health – lead reduction cyst reduction, VOC reduction, etc.


Reverse osmosis System

TDS reduction (mandatory), health claims – lead reduction, cyst reduction, VOC reduction, etc


Ultra-Violet system




TDS reduction (mandatory) health claims – Lead reduction, cyst reduction, VOC reduction, etc.


Water softener system

Hardness reduction (mandatory) health claims – barium reduction, radium reduction


Shower filter system

Free available chlorine reduction