Problems of RO Water Purifiers
The disadvantages and problems of RO water filters and purifiers are that it requires high water pressure and that some water is wasted in the reject stream. If there is not enough pressure in your pipeline then a small electric motor is required to pump the water to a high pressure. So RO water purifiers need electricity to work. Secondly, RO purifier wastes some water in its reject stream which carries all the concentrated impurities that was there in the water originally. But the benefits of RO water purifiers far outweigh these minor problems of RO water purifiers.
Thus when an RO water purifier purifies say 1 liter of water, it drains away about half to one liter of water, in which all the impurities are concentrated. This waste water is known as the reject. This reject quantity of water goes up as the water becomes saltier or has more TDS. For seawater the recovered permeate or product water is only about 30% and the wasted reject water is 70%. Normal home water supplies will get about 50% product or permeate pure water and the waste reject will be about 50%. It may be possible to make use of the reject water, like for cleaning or watering plants.
Is RO water is not good for health, is there any health problems with RO water
Claims that RO water is not good for health is made on two points, one that RO water has no essential minerals in it and secondly that RO water is not good for health because it is too pure like distilled water. It is true that RO water filter removes all the impurities in water including all bacteria, germs and at the same time removes the dissolved salts in the water. So is there any truth in the claims that RO water is not good for health? does it mean that RO water has no minerals and therefore, RO water is not healthy? This is not true!
Essential Minerals in Drinking water
You can never get enough essential minerals from drinking water alone. Minerals required by our body has to come from food we eat, not from the water we drink.
We will prove this to you by putting some figures to this. WHO recommends that drinking water should not contain more than 500 ppm (parts per million) of TDS (Total Dissolved Solids). 500 ppm is the same as 500 milli-grams in a Litre of water. A liter of water weighs 1000 grams = 1,000,000 milli-grams (mg). Assume we drink 2 liters of water a day, so the total mineral content that can possibly be got in the worst drinking water is 1000 mg. (2 liters at 500mg per liter of water). Of this normally more than 60% will be the highly soluble sodium salts which are not an essential mineral - you get plenty of Sodium in your table salt. That leaves 400mg of mineral salts other than sodium in 2 liters of water. Assume it is all Calcium, an essential mineral, so the maximum Calcium salts you can get from drinking 2 liters of the worst possible hard water is 400 mg as Calcium bi-Carbonate, which equates to about 160mg as elemental Calcium. Eating one slice of bread or one chapatti will have more calcium - wheat flour is fortified with calcium in most countries.
We are talking about the worst possible drinkable hard water - If you have 200 ppm calcium in your water, it is very hard water which will not taste good. Other than Calcium, the other essential minerals you can get from water are things like iron, magnesium, etc. Iron, even in very small quantities like 1 ppm, makes the water discoloured and taste very bad. All water purifiers try their best to get rid of it. So to put it bluntly, it is impossible to get enough minerals required by our body from our drinking water. The essential minerals required by our body have to come from food.
One important point to mention here. The RO water filter is doing its job of purifying drinking water by getting rid of all the salts in the water. This includes all toxic chemicals like Arsenic, Mercury, Heavy metals, Nitrates, etc. which can cause great health damage. In this process of removing the poison chemicals from water, it also removes essential minerals. This loss of essential minerals in water is insignificant when you compare it with the benefits of being sure that your water is free from all poison chemicals.
So yes, RO water is too pure, like distilled water, without any minerals, but it is good for health because you are sure you are not getting any poison chemicals in your drinking water. You can get plenty of essential minerals from the food you eat. Also good RO water Purifiers have a remineralising cartridge which can add minerals to the pure RO water at the final stage to remineralise the RO purified water with purified essential minerals like Calcium.
Essential Minerals can be added to RO water
RO water is like pure distilled water that is 100% water without any dissolved salts. All RO water purifier manufacturers are aware of this, so some RO water purifiers have a Cartridge called a remineraliser cartridge, filled with purified alkali essential mineral salts of Calcium and Magnesium, through which the pure RO water passes through. Thus the pure RO water dissolves some of the essential minerals from this remineralisation cartridge or an alkalizer to give alkaline RO water. The alkaline RO water is good for health.
Another method of adding mineral salts to purified RO water is to use a portion of the RO reject water to pass through an ultrafiltration cartridge and then blend it with the pure RO water through a blending valve. This is not a recommended method in areas where there are known contamination of poison chemicals like Arsenic, because the purified reject water used to reharden the RO water may contain Arsenic. So water purifier manufacturers who use this method of rehardening makes sure that your raw water does not have Arsenic or other such dissolved poison chemicals. Passing the RO water through the final remineralisation cartridge is the preferred method.
Water wastage in RO water purifier, how much water is wasted in RO water purifier
RO water purifiers waste some water while purifying the water. Reverse Osmosis process divides the incoming water into two streams - purified water stream and the reject water stream in which all the impurities that were in the original water is rejected. This process of separation and rejection of the impurities in water is done by the RO membrane.
Some RO water filter purifier manufacturers say no wastage of water in their RO water purifiers. What they do is to have a sperate tank into which the reject water of the RO water purifier is stored. You then use this water for purposes like cleaning the floor, watering plants, etc. You can reuse RO waste water by putting the reject RO waste water plastic tube into a bucket, instead of directing the RO waste water tube to the drain. The bucket will get filled as you use purified RO water and you can use the water in the bucket for other purposes where purified water is not necessary.
Maintenance cost of RO water purifier in India, annual maintenance contract of RO water purifier in India
The maintenance cost of RO water purifiers involves the changing of all the cartridge elements in the RO water purifier like the pre water filter cartridges, post carbon filter and remineralizer cartridge. These are not that expensive and actually when you buy the RO water purifier, the water purifier company that sold the water purifier to you will have a service package to maintain the RO water purifier you bought from them. Normally the annual maintenance contract of RO water purifier in India is between 5 to 10% of the value of the RO water purifier to be paid when they do the anual maintenance of the RO water purifier.