What is osmosis?
Osmosis is the movement of water molecules through a semi-permeable membrane down a water potential gradient. More specifically, it is the movement of water across a selectively permeable membrane from an area of high water potential (low solute concentration) to an area of low water potential (high solute concentration). It may also be used to describe a physical process in which any solvent moves, without input of energy, across a semipermeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Osmosis is most commonly observed in plants. If you don't water your plants they wilt. A plant cell is a semipermeable (water flows through the membrane but salts don't) membrane with the living stuff on the inside in a salt solution. Water is drawn into the cell from the outside because pure water will move across a semipermeable membrane to dilute the higher concentration of salt on the inside. This is how water is drawn in from the ground when you water your plants. If you salt your plants (over fertilize or spill some salt on the grass), the plant will wilt because the salt concentration on the outside of the cell is higher than the inside and water then moves across the membrane from the inside to the outside.
What is reverse osmosis?
Reverse Osmosis or "RO" is a process where water is demineralized using a semipermeable membrane at high pressure. Reverse osmosis is osmosis in reverse. To reverse this process, you must overcome the osmotic pressure equilibrium across the membrane because the flow is naturally from dilute to concentrate. We want more pure water so we must increase the salt content in the cell (concentrate side of the membrane). To do this we increase the pressure on the "salty side" (or the side with a high amount of dissolved solids) of the membrane and force the water across. The amount of pressure is determined by the salt concentration. As we force water out, the salt concentration increases requiring even greater pressure to get more pure water.
How does RO water compare to bottled water?
Most bottled waters use natural spring water as their source and therefore typically contain a high mineral content. Some bottled waters (e.g., Dasani and Aquafina) do incorporate RO technology; however these are typically supplied in single use bottles. A home RO system will produce water with as good a result as the bottlers who do use RO technology and better than those who do not. This is all done at a fraction of the cost of bottled water!
How effective is RO technology when compared to other filters?
One must remember that an RO system is comprised on many stages of filtration and not simply an RO membrane by itself. As a result, the RO system provides a staged approach to filtration. Sediment filters first remove the large particulate matter that could potentially clog the membrane. Next, the water enters a carbon filter to remove the chlorine taste & odour. Then the water enters the RO membrane to reduce the level of total dissolved solids and finally the water passes through a final carbon filter prior to being dispensed from the faucet to eliminate any trace odours and remove any volatile organic contaminants (VOC's). Reverse osmosis technology is considered a top of the line product for home drinking water.
I've been told I can't install an RO system in the country as I have low water pressure, is this true?
No, however you may need to purchase a special system made for rural applications (or others with low water pressure) that contain a special booster pump which elevates the influent pressure allowing the RO system to work. The installation of a non-pump unit in an application with low feedwater pressure will cause problems and is not recommended. As a general rule of thumb, if your feedwater pressure is less than 45 psi, install a system with a booster pump.
I installed my RO system and tried to draw a glass of water and the tank is empty.......why?
The process of making reverse osmosis water is a very slow process. Water is being forced (via pressure) through a membrane and the permeate (product water) is basically being produced on a drop-by-drop basis. In this case, you simply have not left enough time for an adequate amount of water to be produced. That is why every RO system is provided with a storage tank. While the RO is making water, it is accumulated in this storage tank. Typical home RO systems are designed to provide an average family with enough water for drinking and cooking.
OK, I've given the RO enough time to fill my storage tank, but now I've used the water to fill my 5 gallon fish tank and it's empty?
Your home RO system is not designed to fill fish tanks, wash cars, feed your humidifier, or any other application which may require copious amounts of water. Most residential RO systems come with a 2 gallon storage tank which is adequate for the drinking and cooking purposes of an average family. IF you are running out of water, you could add a second tank or purchase a larger storage tank. However, you still may have a demand that simple exceeds the production capacity of a residential RO system. If this is the case, commercial systems are available to meet any of your water needs.
I've been told that RO water is unhealthy to drink, why would someone say this?
Reverse osmosis (RO) has been called unnatural water because of its purity. Detractors claim it is man-made and unhealthy and should only be used for industrial applications and not for human consumption. They say that RO water is too pure and clean to be good because such perfectly clean mineral-free water does not exist naturally on earth. However this type of water does exist, it's called RAIN. Rainwater is water that has been stripped of all minerals and is often one of the purest and cleanest water on earth. People have been drinking rainwater for thousands of years without any negative health effects. Only recently has rainwater been polluted by the industrial age and man's pollution of the skies. In the absence of heavy natural or man-made air pollution, rainwater can be very pure and safe to drink. While rain water may absorb and pick-up some substances as it falls through the atmosphere, minerals are not one of them. Thus people have been drinking mineral-free water for thousands of years, which is very normal when you consider that nothing is more natural than Mother Nature's life giving rain. With the scientific research that has been done over the past 40 years on reverse osmosis water, none has ever documented any negative health effects from people drinking RO water. In fact, RO technology has also been extensively tested in the past by the US military and is approved for and highly used throughout the military as drinking water by the men and women in our armed forces.
My ice cubes are the worst, will an RO system make good ice?
Absolutely!!! Cloudy ice cubes result when water is frozen quickly, or when the water is high in dissolved solids. When water is cooled to its freezing point, and ice starts to form, dissolved gases can no longer stay in solution and come out as microscopic bubbles. However, as ice floats in water, once there is enough ice to form a layer on the surface, the ice layer traps all bubbles within the ice cube. RO water eliminates these common problems producing hard, clear cubes that dissolve slowly in a drink. Once you've had RO ice cubes, you'll never go back!!
I've read that RO water leaches minerals from the body, is this true?
Water is called the universal solvent as it always "wants" to have substances dissolved in it. The purer the water, the more aggressive it becomes in attacking things that can dissolve. This doesn't hurt the human body, because our physiology quickly obtains homeostasis using saliva, stomach fluids, etc. to equilibrate all bodily fluids. Reverse Osmosis technology was created in the 1970s and has been scientifically tested in every conceivable way since then. There has never been any documented evidence to prove that reverse osmosis treated water can leach minerals from the human body.
How often does the reverse osmosis membrane need to be replaced?
With proper maintenance of your sediment and activated carbon pre-filters, your reverse osmosis membrane should last 2-3 years.
Can I install my RO system on a non-municipal application?
Yes, RO can be installed on both a municipal and non-municipal application. If however you are installing an RO system on a non-municipal application where the water is unsafe to drink or of an unknown quality, then you will need to first treat the water for microbiological contaminants prior to the installation of the RO system. LUMINOR provides a whole product line of UV systems for this application.
RO uses the term "crossflow"....what does this mean?
The term crossflow refers to the ability of an RO membrane to continually clean itself while it is making permeate (product water). It does this by allow some of the water to pass through the semipermeable membrane while the rest passes over the membrane, downstream and swiping the rejected contaminants down the drain. This prevents contaminants from backing up against the membrane and prematurely clogging it.
Can I install an RO system by myself?
Yes, if you are comfortable with basic plumbing skills and have some "do-it-yourself" skill, the installation of an RO system should take no more than a few hours.
Your system comes with an air gap faucet, what is an air gap?
An air gap is a clear vertical space between the end of the drain line and the flood level rim of the kitchen sink. An air gap is used to prevent cross contamination between the RO and the drain line and is required by your local plumbing code.
I would like to use my own air gap faucet that matches my other faucets, is this a problem?
No, as long as the faucet you are using is of an air-gap design and meets your local plumbing code requirements, there is no problem with changing the faucet.
There is no room under my kitchen sink for the RO, can I install it somewhere else?
Although specifically designed for installation under the kitchen sink, The RO and storage tank can be installed in an alternate location if so desired. In doing so, the placement of the storage tank is the most critical in this type of application as the storage tank carries a precharge of 7-10 psi when empty and if the tank is installed too great of a distance away (both vertically and horizontally), then it will be difficult to obtain water flow to the faucet. If possible, it is recommended to install the RO system and storage tank in a space directly below the kitchen sink and near the rafters so it is close to the sink. By doing this, the storage tank should have little difficulty in delivering water to the faucet. Additionally, you will have to create a separate air gap for the drain line, possible into a laundry tub or sump hole.
In reading the literature, it seems that RO removes virtually everything......I thought minerals were good for me?
Minerals are good for you, however the process of reverse osmosis is not selective in regards to the ions that are removed. The RO system will remove iron and magnesium from your water as easily as it will remove the lead. My body does want the iron and magnesium but it doesn't want the lead. Your body should already be getting all of the nutrients such as essential salts, vitamins, and other trace minerals from the food you eat and the other beverages you drink. The water that you consume should be for hydration purposes only and need not be a source of your vitamins or minerals.
Why does my RO make a gurgling sound from the faucet?
The gurgling sound is emanating from the air gap faucet. As the reject (drain water) is passing over the physical air gap in the faucet and attempting to pass back down to the drain, it is not doing so in an unimpeded manner. The likely problem is from and drooping drain line, rather than a drain line that follows a direct path from the faucet to the drain saddle. To eliminate this problem, make sure the drain line (black line) has no droops or curves and follows a direct path.
Why is there water coming out of the base of my RO faucet?
Quite simply, your drain line is plugged and the air gap faucet is doing exactly what it was designed to do and that is to prevent contamination between the sewer and the potable water supply. The likely culprit is some food waste or debris clogging the exit hole in the drain saddle. Remove the connection to the drain saddle and remove the clogged debris. You may also find that the drain hole is simply not large enough. Ensure that the drain hole is at least 3/8" in diameter.
The RO seems to waste a lot of water. Is this normal?
The simple answer is yes and no. The technology behind RO uses water to make pure water. The permeate (product water) is stored in the pressure tank and the brine (reject) water is sent to the drain. A typical residential RO system works on a recovery rate of about 25%, meaning for every gallon of clean water produced by a RO system, an average of 4 gallons of brine water is used and discarded. This brine (waste) water is constantly used by the system to clean the membrane and allows the filter to work effectively and last for many years. Remember, RO systems clean your water and remove thousands of unhealthy contaminants from tap water that countertop and faucet filters cannot. Reverse osmosis brine water is the equivalent of an extra 3 to 4 toilet flushes a day. You actually waste more water each day when you wash your dishes or clothes than from a RO system. You will probably pay an extra 25 to 50 cents a month from RO waste water. Waste water from RO systems is actually pretty clean and similar to tap water in purity levels. It can be channelled for use in gardens watering plants or stored and used for other household applications. The truth is, there is no "new" water on this planet. All water is old water that has been recycled continuously for millions of years. We are actually drinking the same water that the dinosaurs drank, recycled obviously by Mother Nature.
Aren't all RO systems the same, just with a different manufacturer's label?
Absolutely not. Like all water filters, the effectiveness of a reverse osmosis system depends greatly on the quality of its components - especially its pre-filter cartridges (quantity and quality) and the membrane itself. Lower quality pre-filters will suffer from premature membrane fouling, as well as reduced performance, purified water output, and membrane life.
Why are reverse osmosis systems always combined with carbon and sediment pre-filters?
The only major category of contaminants that reverse osmosis is not highly effective in removing (organic compounds) is specifically targeted by activated carbon filters. Pre-filters also prevent the reverse osmosis membrane from being fouled or clogged by sediment, chlorine, and other contaminants, thereby enhancing its effectiveness and lifespan.
Will my RO provide me with disinfection for my water?
No, although the pore structure of an RO membrane is small enough to prevent most bacteria and virus from passing through, RO systems are not considered safe for a total disinfection regime. There may be potential cracks in the membrane where microorganisms can potentially travel through as well as a possibility to bypass some of the seals in an RO system. To ensure proper disinfection, install a LUMINOR UV system prior to your RO system.
What does the term "TDS creep" mean?
TDS creep (total dissolved solids creep) describes a phenomenon that can occur if differential pressure in a reverse osmosis system across the membrane is removed and is evidenced by the presence of salt concentration in the effluent when the unit is returned to service, after being shut down for a period of time.
Is it possible to have a whole house RO system?
Yes, this is possible, it would however need to be an engineered system built to accommodate the total capacity needs of the application. It would likely be a very large commercial type system with special piping running throughout the house to accommodate the low pH of RO water. It can be, and is done, however at a considerable expense.
Why do I need to use polyethylene tubing for the water coming out of my RO?
As RO systems can remove most of the total dissolved solids (TDS) in the water (>97%), the resulting water is very aggressive in nature and can cause leaching issues if used on copper piping. Typically, the purer the water, the more aggressive it becomes. In some extreme cases, a pH adjustment may be necessary to raise the pH of the RO water.
Are RO systems effective in the removal of arsenic?
RO is one of the technologies to successfully remove arsenic form the water supply. It should be noted that if you are choosing an RO system to remove arsenic, you should choose an RO system that carries the NSF (NSF International) approval for arsenic removal.
I'm told that temperature adversely affects an RO system, is this true?
Yes, an increase in feed water temperature increases the permeate flux, but does not affect the permeate (product water) quality. Depending on the selection of membrane material, this temperature effect may be from 1.5% to 2% per degree Fahrenheit.
Is pre-treatment necessary with an RO system? What substances can negatively affect an RO membrane?
Without proper pre-treatment an RO system will certainly face problems with membrane longevity. Membrane fouling can come in both organic and inorganic forms. Organic fouling can be in many forms including those of a microbiological nature, while inorganic fouling can be caused by suspended solids, calcium sulphate, bicarbonate alkalinity as well as iron, manganese, silica, aluminum and other colloidal material. Proper pre-treatment is necessary to ensure the maximum life of the RO membrane.
My water has a TDS of 2000 ppm, its temperature is 5°C (41°F), and I have a pressure system that delivers 45 psi, I should have no problems with my 50 gpd RO system with a thin film composite membrane....right?
Not exactly....the output of all RO systems are tested at 25°C (77°F) and at a specific pressure which can vary from manufacturer to manufacturer (in this case LUMINOR will assume a FilmTech membrane which has a Rated System Pressure of 50 psi). All three of these parameters (TDS, temperature & pressure) will affect the amount of water produced by the RO. To answer this question we must first calculate the Temperature Correction Factor (TFC) maximum daily production (in GPD) of the membrane. To do this, we need to refer to the chart below and select the TFC for a thin film membrane at 41°F, which is 2.58. Now we take the Rated Pressure (Pr) and divide this by the TFC and get 17.4 (45/2.58=17.4) Therefore, with these given water conditions, the TFC Adjusted Flow (maximum production of the membrane) is now 17.4 GPD, simply to account for the cold water. Now we'll look at the pressure side, but first we have to account for the TDS. For RO to function, a minimum pressure of 1 psi is required for every 100 ppm of TDS. In this case, 15 psi of pressure is needed to force a single drop of water through the membrane. This is known as Osmotic Pressure (p) and is calculated by the equation (p = TDS/100). In this case, the Osmotic Pressure is 20 psi. Next we need to calculate the Net Pressure Rating (Pr) which is the Rated System Pressure (Ps) minus the Osmotic Pressure (Pr = Ps - p). In this case the Net Pressure Rating is 30 psi (50-20). We also need to calculate the Net Operating Pressure (Pn) which is the Applied Pressure (Pa) minus the Osmotic Pressure (Pn = Pa - p). In this case the Net Operating Pressure is 25 psi (45-20). To calculate the amount of Expected Production we need to take the Temperature adjusted flow and multiply it by the division of the Net Operating Pressure and the Net Pressure Rating (TFC Adjusted Flow X (Pn/Pr)). In this case, the net Expected Flow would be a total of 14.5 GPD (17.4 X (25/30)). So under these conditions, the maximum water that can be produce by this system in a 24-hour period is 14.5 gallons. Ultimately you would have to determine if that was enough or not. Bottom line is to be aware that the rated capacity of the system and the actual amount of water that you will get from the system are nowhere close.