Reverse Osmosis Guide

What is Reverse Osmosis?

In very simple terms, Reverse Osmosis (RO) is a means of filtering out everything from water. By everything we mean contaminants, dissolved salts, particles, parasites, bacteria, molecules, minerals - everything that has been dissolved in the water including salt (in de-salination plants) and bacteria, viruses, and micro plastics. What you are left with is pure water, literally pure H20. Reverse Osmosis is a process.

Reverse Osmosis is commonly used by the pharmaceutical, manufacturing and metal finishing companies, as well as within food and beverage production, water jet cutting and glass, boiler, and cooling tower pre-treatment processes. Notwithstanding hospitals, doctors and dentists using RO technology to produce pure H20 for their sterilisation needs. However, it also has an application in a domestic environment and many people are now turning to RO water for their drinking water to ensure they are drinking virus, micro plastic and bacteria free water.

What exactly is it?

If you can imagine a series of ultra-fine filters that remove just about everything from the water, leaving a very pure product, that’s RO.

RO systems normally have several filters that work in line, processing the water from a high grade of membrane through to the finest membrane to filter out everything. These filters are measured in microns. To put the grading into perspective a human hair is 70 microns in diameter; the naked eye can see down to 40 microns; a white blood cell is 25 microns and a red blood cell is 8 microns. When we start talking about bacteria, we are moving into the 0.5-2 microns parameters with smaller viruses in the 0.1 micron region. So, you can see we are talking about the removal of some seriously small stuff.

A simple RO system will have a 5 micron and a 1micron filter, carbon filters and finally a membrane which can remove contaminants down to 0.001 microns. That is very small.

RO’s have many applications from some serious filtration at an industrial level – think food and drink processing where its vital that all the contaminants are removed from any water needed in production, to medical needs – hospitals, doctors and dental surgeries where pure water is vital to ensuring that sterilisation is effective and to domestic applications where it is necessary to ensure that the purest water supply is available. This can be a medical requirement, a concern about water quality in general or even possibly a taste and smell concern. Even keen aquarium enthusiasts demand RO systems to keep their fish in the best possible health.

How does it work?

For simplicity, lets have a look at how a straightforward domestic RO system works.

Firstly, you need a water supply that is provided under pressure to the RO system. This can be municipally supplied water or water from a private supply, such as a well. Our standard municipally supplied water comes to us via the water main. This will normally be sent to our houses at about 40 – 60 psi or 2.75 – 4.12 bar.

Without pressure we would not have water coming out of our taps as pressure is the force that pushes water through pipes. Water pressure determines the flow of water from the tap. An RO system needs pressure to work. If you have high water pressure, more than 3 bar, then you can use a non-pumped system. If your water pressure is lower than 3 bar or you are not sure, it is recommended you use a pumped system. Pressure must be reduced if it exceeds 6 bar.

An RO needs pressure to literally force the contaminated water through the filters and membrane, leaving the small particles, micro plastics and contaminants on one side of the membrane to be sent to waste, via the rejected water solution. Without pressure, this process cannot occur.

You can have many different types of systems; tanked with a pump, tanked without a pump (direct flow) easy change filter type, compact systems (to fit in small spaces). If you are considering an RO system, its worth consulting an expert supplier for advice on the best type for your application.

Let’s have a look at a common tank version.

The water enters the RO system and passes through a number of filters - usually a 5 micron filter, then a carbon filter, followed by a 1 micron filter. Water then passes through the 0.001 micron membrane and into the holding tank. When the RO tap is turned to demand water, this passes through a ‘polishing’ filter of activated carbon as the final stage.

As water is drawn from the tank, more RO water is processed to top up the tank, waiting for the next time you need your RO water.

How long will the water last in the tank?

If you are using your RO water on a daily basis, your tank will just replenish or top up each time you use water. Bear in mind that it does take time for the water to be replaced in the tank and if you have high demand for RO water, you need to make sure that you have a system that is capable of delivering enough water for your household or application. Check before you buy to ensure the system you are interested in will meet your needs.

If you leave your RO system for any period of time, its recommended that you drain the tank and switch it off. When you return to your system you simply switch the power/water back on and allow the system to refill.

Is there much wasted water with a RO system?

The answer to this is that it depends on the RO system. Typical systems may send as much as 2/3rd of the processed water to waste, however more modern systems are much more economical in the ratio of wastewater to RO water. It is possible to divert the waste water to other applications within a household, such as flushing toilets or to be used in washing machines and dishwashers, therefore reducing the amount of water that is sent directly to waste.

Are RO’s one size?

RO’s come in many shapes and sizes. You can buy under sink systems or countertop versions. You can get ones that are portable and can be moved around with you. However, it is worth checking the dimensions of any unit you are considering buying as you need to make sure you have sufficient space for it – whether it be the under sink or counter top type. The other thing to remember is that you must allow space to change both the filters and the membrane – which must be done on a regular basis. You will need to access the filter pods approximately every 6 months and the membrane every 18 months.

Do I need a plumber to install a RO?

The straight answer is that if you are competent in turning off your water supply, following simple instructions – written or via a video and are happy with various plumbing DIY terminologies then it should not cause a problem for you. However, if you are none (or not all of the above) then it is recommended that you ask a competent handyman or a plumber to assist you. The level of expertise of a plumber with the installation of water treatment products is subjective and it might be worth asking the question about previous RO installation experience before engaging a professional. Remember, installation time is your money and if you have someone sitting reading through instructions before the installation (which you will be paying for) it might be worth qualifying RO experience before engaging a tradesman. Having said this, there are many videos available online to assist your installation, should you need it.

How often do I change the filters?

Your filters will need changing every six months, regardless of how often the RO is used during this period of time. So if you have a RO installed in a holiday home and only use it whilst you are there, you do need to make sure the filters are changed regularly as they will deteriorate over time once they have had water through them. In addition, if the RO is left standing for a period of time and not used, there may be a slight taste/odour detected when you switch the unit back on. This is usually simple to remedy - simply run the RO and discard the first full tank of water. Allow the RO to refill and your water should be fine. The membrane will need changing every 18months and the same parameters apply as with the filters.

What does RO water taste like?

How do you even begin to explain what a slice of toast tastes like to someone who had never tasted bread let alone toast? The best analogy I can think of is that RO water tastes like stripped water, or ‘thin’. Its like diluted water. We are used to drinking water that has minerals in it, which gives it a certain taste and sometimes smell. We have become accustomed to this water that we take straight from our tap. If you chose to drink filter water or mineral water, it will still have the minerals present in it which has its own distinctive taste and a certain smoothness to the palate.

RO water is different. It is stripped back, pared down to bare water. RO water has a certain composition which isn’t to everyone’s taste. It is difficult to define but it is definitely different. However, for some people RO water is about life and death as they cannot risk drinking ‘normal’ water from the tap or bottle and so it is something that they may have to become used to.

It is possible to add minerals back into the water after everything has been processed out, so improving the taste of the end product. Its best to speak to your RO provider for advice about this if you are concerned about taste

In summary - What you need to know about RO water

  • RO systems put water under pressure and force it through a series of filters and membranes which result in pure H20
  • The RO process will remove viruses, bacteria, micro plastics and just about everything else from the water – leaving pure H20
  • RO systems need to process a lot of water in order to achieve the end result. Your water bill may increase.
  • RO systems vary in size and how they work – the best option is to ask an expert supplier and get help with what you want to achieve
  • RO systems can be installed by a competent DIYer or a plumber
  • Depending on the type, RO systems need space to install in your kitchen/boat/caravan/other application
  • Once you have purchased your RO, you need to ensure its well maintained by replacing filters and membranes on a regular basis
  • RO water tastes different from other water sources

Is RO water good for you?

RO is the finest filtration method for water and leaves you with the purest form of water possible. By filtering out all the unwanted molecules such as lead and chlorine, chloramines and pesticides as well as bacteria and viruses, although its clean and safe for drinking certain trace minerals and elements are removed. For people with serious illnesses and health concerns or even allergies, using RO to ensure the safety of drinking water can be of high importance.

Tap water

You might be surprised to learn that much of the water that flows through our municipal network of water pipes on its way to our houses has been ‘used’ many times before. Even in the UK, water is regarded as a finite resource and as such needs to be treated carefully. For many years now, water that is taken from our roads, soakaways and even from households is ‘recycled’. We are not consuming pure rainwater or water that has come from a natural source when we open our kitchen tap for a glass of water.

It is widely understood that there is not a water molecule on the planet that hasn’t passed through a living organism, at least once! Water from rivers tends to have been through more bodies than rainwater, because it is concentrated by being in a channel. In a highly populated area such as the Thames valley, water will have been through human bodies several times by the time it is reused. This accounts for female hormones from birth control pills being detectable in London water; a phenomenon that is not exclusive to London, either. 

Our drinking water is treated to enable it to meet the requirements of the Drinking Water Inspectorate which was formed in 1990 to give independent reassurance that the many water companies around the UK are supplying water to correct minimum levels. However, and it’s a big however, the minimum requirements for the quality of our water are very much subjective.

In the UK, our drinking water is treated to kill harmful bacteria and to keep water germ free on its journey to our taps. The use of chlorine is the most common method of disinfection, but it can react with certain naturally occurring organic compounds. It is a legal requirement that our drinking water is monitored for these dangerous compounds so the chances of consuming any harmful substances is extremely small. However, it does impart a very strong chemical taste and smell which can be unpleasant. In addition, the closer a property is to the water treatment plant, the more likely that chlorine (both smell and taste) can be detected in the water. There is also the additional concern that the prolonged use of chlorine in drinking way may be linked with an increase in risk of colon and bladder cancer.

The difficulty with tap water is that it is pumped into our homes using a network of pipework that was laid in the last century and in some cases even earlier. Much of this network is still lead either as a connection to the water main or as an integral part of the household plumbing. Whilst lead is no longer found in petrol, food containers and paint, it stands to reason that  where water travels through lead pipes, it may become contaminated over a period of time. Even small amounts can cause serious health problems. There does need to be a significant investment in the water supply substructure which would then ensure that it is fit for purpose and protect both the environment and personal health. More worryingly than lead, much of our drinking water is now contaminated with micro fibres (microscopic plastic).

So you can see that our drinking water in the UK is very much a ‘soup’ of chlorine, microplastics, lead, fluoride, bacteria, pesticides and other chemicals. We are told that here in the UK, that tap water is safe to drink but given the number of contaminants that our tap water contains plus the fact that it has been ‘processed’ a number of times we can have a look at the question again ‘is RO water good for you?’ I think I would be opting for RO water every time.

So what is best? Tap or RO drinking water?

RO systems produce the purest water possible by removing all molecules and contaminants within the water, however the system cannot differentiate between good and bad molecules and nutrients and minerals will be removed in the process, literally stripping the water right back to basics. It is of course possible to get all the nutrients we need from food but cooking with de-mineralised water can have a negative effect on the amount of vitamins and minerals in the food. However, all is not lost as you can place a re-mineralising filter on an RO which will put vital minerals back into the water.

RO water benefits

RO water is the produced water from a RO system. RO is the finest filtration for water producing the purest form of water possible. These systems will filter out 98% of unwanted molecules such as fluoride, lead, chlorine, chloramines, pesticides and many more. Once this process of filtration has taken place the produced water will be expertly clean, safe for drinking and storage for future use also. With regular maintenance, filter and membrane changes a RO system will provide pure water for the life span of the system.

While we are fortunate enough in the UK to have ‘safe’ drinking water pumped to our homes, some areas may still have potential issues and concerns over the use of pesticides or herbicides. In areas where the quality of water may be uncertain RO water is an excellent option for removing trace minerals. For people with serious allergies, illnesses and health concerns using RO to ensure the safety of water can be of high importance. This will produce very high quality water removing just about every contaminant possible giving reassurance to those who may require it.