What is Reverse Osmosis?

Reverse Osmosis is a technique which separates the very smallest particles, molecules and ions. Reverse Osmosis improves over conventional filtration techniques.

With conventional techniques very few pollutants are removed compared with Reverse Osmosis which separates a percentage of pure water and rejects all the substances which the water contained before undergoing the Reverse Osmosis process.

Osmosis is the phenomenon of water flow through a semi-permeable membrane that blocks the transport of salts or other solutes through it. Osmosis is a fundamental effect in all-biological systems. Osmosis is applied to water purification and other chemical laboratory and industrial processes. When two water volumes are separated by a semi-permeable membrane, water will flow from the side of low solute concentration to the side of high solute concentration.

The flow may be stopped or even reversed by applying external pressure on the side of higher concentration. This is called Reverse Osmosis. Reverse Osmosis is only one stage of a typical RO system. Sediment and carbon filtration is normally included with a RO system, with each stage of filtration contributing to the purification process. Deionisation may also be employed as a final product water polishing stage. Using a mixed bed resin will remove any remaining pollutants from the RO process.

1. The first stage of filtration is the sediment filter, which reduces suspended particles such as dirt, dust, and rust.

2. The second stage of filtration is the carbon filter, or filters which reduce volatile organic chemicals, chlorine, and other taste and odour causing compounds. Chlorine is damaging to an RO membrane therefore the carbon stage is particularly important.

3. The heart of Reverse Osmosis is the membrane. It is responsible for rejecting up to 99% of the total dissolved solids in the water. This is where the purification takes place.

4. Deionisation cartridges may be included in your Reverse Osmosis system, our cartridges use semiconductor grade mixed bed deionisation resins used for the demineralisation of aqueous solutions.

The average household tap water usually contains somewhere between 50ppm-750ppm (parts per million) of dissolved mineral solids, 80ppm being good quality; for tap water; and 450ppm+ being of lesser quality. The scale below gives a visual representation of the TDS scale.

Tap water is forced through the RO system with your existing household water pressure, typically somewhere between 40-65psi. This line pressure allows the Reverse Osmosis process to take place. Purified water from one side of the membrane is collected as required. The concentrated wastewater from the other side of the membrane is flushed to drain.

The purified, (RO), water is used for your requirements. The Reverse Osmosis system operates until a holding tank is filled, after which an automatic shut-off valve (if fitted) suspends the operation until the purified water is consumed. When purified water is taken from the holding tank, the system automatically begins producing more water until the tank has been filled again.

All Osmotics systems incorporate TFC, (Thin Film Composite), Membranes which will produce between 1.0- 10.0 gallons of purified water an hour. Production rate depends on the RO system supplied and water supply characteristics. Typically it takes anywhere from 3-6 gallons of tap water to produce 1.0 gallon of RO water, depending upon the household pressure, total dissolved solids, and the temperature of the tap water. The membranes in our Reverse Osmosis systems are tested with an industry standard of 60psi, 77 degrees F. , 200ppm TDS, If your water pressure and temperature vary from the testing standard in either direction, the RO membrane may produce slightly less water.

What is meant by total dissolved solids?

 In the natural cycle of water, water that began its life as rain and eventually found its way to your tap has come in contact with many sources of potential contaminant. The various minerals and salts that have been dissolved by the water during this ‘water cycle’ are called Total Dissolved Solids (TDS).

Total Dissolved Solids (TDS) are the total weight of all solids that are dissolved in a given volume of water, expressed in units of mg per unit volume of water (mg/litre), also referred to as ‘parts per million’.

TDS measurements can be used to determine the overall purity of a water supply. The lower the TDS reading, the purer the water. Higher TDS readings are indicative of existing impurities in the water.

What type of mineral contaminants are removed by Reverse Osmosis?

Reduction of mineral components that make up total dissolved solids will vary up to a maximum of 99.8% depending on water chemistry and pressure.

The Osmotics Installation and Maintenance manual contains typical membrane rejection rates for typical mineral components found in domestic water supplies.

Does RO remove parasites such as Bacteria, Cysts Or Cryptosporidium?

While a health claim cannot be made because of intangibles such as regular maintenance, these items are too large to pass through the TFC membrane. NSFs rating for reduction of Giardia Cysts and Cryptosporidium is 1 micron, and the TFC membrane filters down to 1/10,000th of a micron. That is 10,000 times smaller than these parasites.

Is water wasted with RO Systems?

There is a certain percentage of water from the system that goes to the drain. This water is carrying away the impurities. These particles are too small to be caught by the filters. Osmotics.co.uk can supply an automatic shut-off valve that shuts off the flow of water to the drain when the holding tank is full. This valve stops the RO system from continuously running water down the drain, thus conserving water via the RO system working only according to usage.

What happens to the impurities that were in the water?

They are discharged to the domestic drainage system. Unlike filters, the RO membrane is self-cleaning. As the source water flows through the membrane housing, it is divided into two paths. One path is forced through the membrane by osmotic pressure created due to the water pressure on each side of the semi-permeable membrane. The second stream carries the rejected salts, dissolved pollutants and contaminates to the drain. Therefore, there is a minimum accumulation of debris on the pressure side of the membrane. Charcoal or carbon filters, on the other hand, become less efficient with each glass of water drawn through them. Carbon filters only remove a limited number of contaminants, some odours, and some tastes.

What is the ratio of wastewater to the pure water produced by an Osmotics Reverse Osmosis System?

The typical ratio is 4 to 1, dependant on incoming water temperature and pressure.

Can the waste water be saved and used?

The drain water is slightly higher in TDS concentration than the incoming water, but as the RO process does not add anything to the water, it can be used to water your lawn or garden.

What is the importance of water pressure to an RO System?

It is the pressure of water that forces the it through the membrane for purification and flushes the rejected solids away. Low water pressure will result in reduced production and premature fouling of the membrane. The ideal pressure for operating an RO system is 60 psi. Pressure below 40 psi is generally considered insufficient, and should be boosted using a pressure booster pump.

Is it necessary to change the filters in the Osmotics RO System every six months?

Yes. It is highly recommended. The Osmotics RO system has been designed to operate at its best and give high quality purified water with normal routine maintenance. By changing the pre-filters on a regular six-monthly basis, you will eliminate dirt and chemicals such as Chlorine in the water that will attack the membrane. After six months of use, the carbon filters may have bacteria growing within the filter media. Your local water conditions may necessitate more frequent filter changes. A system pressure gauge on the outlet of the pre-filtration section will provide an indication of fouling before the membrane is affected. Pressure gauges are available from the Osmotics online store at www.osmotics.co.uk

Does the RO system have to be mounted under the kitchen sink?

No. The RO system can be mounted in a cabinet to either side of the kitchen sink or even mounted remotely in a garage or basement. If mounted externally, sufficient protection from frost damage must be provided. It is recommended that the system be kept above +5 degrees C.

How will I know the RO System is removing dissolved solids from the tap water?

 You will be able to tell by the taste and clarity of the water. The best way of determining the amount of dissolved solids removed from tap water is by the use of a conductivity meter. This meter measures the conductivity the dissolved solids impart to the water. This is converted on the meter scale into parts per million of Total Dissolved Solids (TDS). TDS meters are available from the Osmotics online store at www.osmotics.co.uk

I have a water softener, does that treat my drinking water?

No. A water softener removes calcium and magnesium from the water and is usually installed in the water supply to the house. A water softener is good for the home plumbing and water using appliances, but does little to improve the taste or quality of your drinking water.

Will a water softener harm the Reverse Osmosis membrane?

No. Calcium and magnesium (lime scale) are two of the hardest minerals for the Reverse Osmosis membrane to remove. Sodium (added to the water by the softener) is much easier on the membrane and it will reject 99% of all sodium in the water. A water softener will help extend the life of the membrane. Osmotics also supply softening pre-filter cartridges which perform the same function as a water softener by using softening resins.

Will an RO System soften water?

Yes. RO water is softened through the Reverse Osmosis purification process; however, hard water (above 7 grains of hardness) will shorten the life of the membrane. The harder the water, the shorter the life.

Is it safe to drink RO water?

YES! RO water is perfectly safe to drink. There is also a scientific explanation as to why RO water is actually better for you than water that contains high mineral (TDS) content.

Water with a high Total Dissolved Solids (TDS), counts of over 50 ppm, actually become electrically charged and can conduct very small amounts of electrical current. High TDS water, under the right circumstances, can actually cause a small electric light bulb to become illuminated!

Water with a high TDS count is typically a base, (slightly alkaline), substance that is lacking in hydrogen molecules, and will search for hydrogen molecules in the body to balance itself. This type of water often causes de-hydration on the cellular level.

Reverse Osmosis water with low TDS on the other hand, has a much lower ability to conduct electrical charges. Typically, Reverse Osmosis water is slightly acidic and loaded with positively charged hydrogen (H+) molecules. This type of water has been scientifically proven to provide superior hydration at the cellular level.

What is the difference between an RO unit and standard water filter?

A conventional filtration system, such as that in a refrigerator for instance, will give you nice tasting water, but it will not remove the Total Dissolved Solids (TDS), such as, SODIUM, MANGANESE, CALCIUM CARBONATE, to name a few, that are present in all tap waters. Only an RO membrane can do this.

Many forms of bacteria are so small, that conventional filters cannot remove them, an RO membrane will.

What maintenance is required on this system?

It is recommended that you change the pre-filters on these systems once every 6 months, depending on the quality of your tap water. If there are not many physical particles in the tap water, you will get upwards of one year service life with the pre-filters. You will be able to tell when the pre-filters should be changed, by the time it takes to produce the purified water. The system will slow down significantly and you’ll notice the holding tank (if supplied) not filling as quickly as it was, with the RO water.

The Reverse Osmosis membrane on our systems are expected to last up to 3 to 4 years before it needs replacing.

When the RO Membrane begins to lose its effectiveness, the water production will slow and the TDS ( total dissolved solids) will gradually start to increase in the purified water. Most water, after it is purified through an RO Membrane will have a 90-99% reduction in TDS. The easiest and most cost-effective way to monitor the efficiency of the RO Membrane is with the use a TDS meter.

We recommend setting up a maintenance schedule for the pre-filters to be changed every 6 months. In addition, replace the membrane and the polishing filter every 18-24 months and you will always have a efficient system that will consistently produce crisp, clean and refreshing, purified water.

Is this system easy to install?

Any person who knows how to use a screw driver, an adjustable spanner and a drill, can install this system in about an hour.

Your system is supplied with a comprehensive and easy to understand Installation Manual. Further installation advice is available via email if required.

You will not have to solder or cut pipes. The system hooks in to the existing plumbing under your kitchen sink with a very high quality self-piercing saddle valve. These special fittings will allow you to install the system without cutting or soldering your pipes.

The remainder of the system is plumbed with FDA approved colour coded, high pressure tubing. The System has Quick-Connect receiver fittings that allow you to just push the supplied tubing into them and they lock and seal automatically.

Your system may also come with a faucet that is easy to install into your kitchen sink.

Why should I measure the TDS level in my water?

The quickest, easiest way to determine if your Reverse Osmosis system is operating properly is to measure the TDS of the feed water vs. the TDS of the product water. A typical residential membrane will reject 90-99% of the feed water TDS and leave your product, (drinking), water very pure.

For example if your feed water contains 200 ppm TDS, your RO water TDS should be between 10-20 ppm TDS.

A digital TDS monitor that can be supplied with our RO systems will allow you to monitor and calculate the salt (TDS) rejection % of the RO membrane. Use the following formula after recording the feed TDS and the product TDS.

SALT REJECTION (%) = (1-(PRODUCT WATER TDS/FEED WATER TDS) X 100

EXAMPLE:

FEED WATER TDS = 500 PPM

PRODUCT WATER TDS =10 PPM

APPLY THE FORMULA AS FOLLOWS:

1. (1-(10/500)) X 100

2. (1-0.02)X100

3. (.98)X100

4. REJECTION RATE = 98% (THIS WOULD INDICATE A PROPERLY FUNCTIONING MEMBRANE)

Water with a high Total Dissolved Solids (TDS) count of over 50 ppm becomes electrically charged and can actually conduct an electric current. Such water will actually cause a small electric light bulb to become illuminated, and of course, will also conduct excessive charges of electricity throughout the body.

High total dissolved solids may affect the aesthetic quality of the water, interfere with washing clothes and corrode plumbing fixtures. For aesthetic reasons, a limit of 500 mg/l (milligrams per litre) has been established as part of the Secondary Drinking Water Standards.

How will I know if my system is working correctly?

When the RO Membrane begins to lose its effectiveness, the water production will take longer than usual and the TDS (total dissolved solids) could gradually start to increase in the purified water.

A properly functioning residential membrane will reduce the TDS from the feed water by up to 99% under optimum conditions.

Measure the TDS in your feed water, let us say its 120ppm, now measure the TDS in your RO water, and it should between 2-30ppm. If it is within this range, your system is functioning efficiently.

When the rejection rate consistently falls below 75%, or the system seems to take much longer than usual to produce water, a membrane change may be necessary.

The easiest and most cost-effective way to test the efficiency of the RO Membrane is to use a TDS meter. We recommend setting up a maintenance schedule for the pre-filters to be replaced every 6 months. Replacing the membrane and the polishing filter every 18-24 months ensures your system will supply fresh tasting pure water consistently.

Osmotics Reverse Osmosis Systems operate within a range of 40-125psi. If you are concerned that there may not be enough water pressure in your home, you can purchase an inexpensive water pressure gauge that will attach to the inlet of your RO Housing. After attaching the gauge, turn the water on fully and read the pressure. If the pressure is lower than 40psi you will need a booster pump for the system which comes completely assembled from the Osmotics.co.uk online store.