Previous: Water Softening and Mineral Removal Next:UV Light Sterilization
|
Information About: |
| Reverse osmosis is a remarkably simple process of purifying water and is well-suited for use in RVs. As the name implies, RO reverses the natural process of osmosis, which is a very important process utilized by living organisms. |
| What Is This Osmosis That You're Reversing? Osmosis is the process of water molecules moving through certain kinds of membranes, called "semi-permeable". If a semi-permeable membrane separates two portions of water, one with pure and one with tap water, then osmosis will occur. The water molecules from the pure water side of the membrane will move through the membrane and dilute the tap water. This is a natural process that does not require any energy to make it work. |
Why Would I Want To Reverse Osmosis? Well, if osmosis is water molecules moving through a membrane from the pure side to the tap water side, then reversing the process causes tap water to produce pure water. In RO, water molecules are forced, with the help of some external energy, to move from a "concentrated" solution (the feed water) through a semi-permeable membrane. And, in an RO system, there is nothing on the other side of the membrane to dissolve in the water, so you end up with pure water. The energy that drives this process is the pressure that the feed water is under. |
| Does RO Purify All The Water? No. Under the best of conditions, including the right membrane and adequate water pressure, about 20 to 30% of the water put into an RO unit will come out as pure water. The rest is called "brine" because it has a higher concentration of contaminants than when it went into the unit. The brine performs the vital function of carrying the contaminants away from the membrane, and it must be disposed of in some manner. |
Is The Purified Water 100% Pure? No. RO does not remove all of the dissolved material from the feed water. Some of the dissolved stuff will pass through an RO membrane, thereby contaminating the "pure" water. The amount that gets through is very small, somewhere between 2 to 20% depending on the age and condition of the membrane. Generally, very few harmful contaminants can pass through an RO membrane. All sediment and most minerals will be removed by RO. |
|
So What Are The Advantages of Reverse Osmosis?
If you use RO for all of your water, you'll get these additional benefits:
|
| How Much Water Will You Process With RO? Reverse osmosis produces highly purified water that is low in minerals and salts. As such, it functions as filter, purifier, and water softener combined into one system. Because of this, more and more RVers are processing all of the water they use with RO. Many others use RO only to purify their potable water for drinking and cooking, and some want a small countertop unit to process just their drinking water. Whatever size system you want, be aware that RO is inherently a low-flow process, so you need to consider some additional factors before deciding which system will best fit your needs. |
| Water Pressure for RO: The More The Better RO requires pressure to force water through a membrane, and the more pressure you have, the better the system will work. You need 40 psi of pressure as an absolute minimum for RO to even work, and 60 psi or higher will enable the RO system to produce pure water at a higher rate and of a higher quality. Also, the membrane, which is the expensive heart of the system, will last longer. If your pressure varies and often falls below 50 psi, we strongly recommend you use a booster pump to keep the pressure to your RO system in the proper range. |
| Brine Disposal: An Important Consideration As discussed above, the brine produced in an RO system must be disposed of. This is usually done by dumping it down the drain. In some situations, this can be a problem for the park's sewage treatment system, so you may need to use it to water the lawn or other plants. The brine is not so concentrated as to harm plants. If you will be using RO while dry camping, water conservation is of utmost concern. In that situation, you can always return the brine to your tank for use in other ways. |
| Will An RO System Last Forever? No. The membranes in RO systems eventually fail and need to be replaced. There are two ways in which a membrane can fail, and you can detect these failures easily. The first type of failure is when the membrane gets plugged with contaminants, and it causes the production rate of the system to drop off. The second type of failure is a breakdown of the membrane itself. This is impossible to see, and difficult to recognize. However, when this type of failure occurs, the contaminants in the feed water will pass right through the membrane. The only reliable way of detecting this type of failure is to measure the Total Dissolved Solids (TDS) of your product water on a regular basis with a TDS meter. If you start to notice an increase from your normal levels, then you probably have a failed membrane that needs to be replaced. |
| Filtering Is Highly Recommended As filtration devices, RO systems are subject to plugging up, and the membranes are sensitive to chlorine. They will perform better and last longer if you pre-filter the feed water to remove sediment and taste-and-odor contaminants. This is best accomplished with a canister system, either as a separate setup or as part of the RO package. If you already have a filtration system in place, you need only buy the Basic RO unit. We also sell combination systems that include thecanisters and the RO unit as a package. These systems include sediment and carbon filters. |
| Storage and Pressurization of the Pure Water The pure water produced by the RO system must be stored for later use,  and may need to be pressurized to make it convenient. How these tasks are accomplished depends on the size of your system. With a countertop unit, you supply a container that the unit fills with purified water. Potable water systems are usually installed under your kitchen sink and require a storage tank for the pure water. We sell 2- and 3-gallon pressure tanks for this purpose. Some pressure is developed by the RO system, but for better pressure, we recommend you include a permeate pump and/or a boost pump in your system. If you want to use RO for all of your water, then unless you have at least 50 to 60 psi of pressure, a boost pump will be essential to provide adequate pressure to the membrane. For a whole-RV system, you will utilize your RV's water tank to store the pure water and the built-in RV pump to deliver the water to your fixtures. You will then be pumping the water out of your tank, acting like you are dry camping, even though you are hooked up to a park's water supply. In this situation, we recommend you upgrade your original equipment pump with a much-improved unit by Aquatec. This improved pump will make your RV experience much more enjoyable by providing quieter operation and higher flow and pressure. |
| Controlling An RO System Whenever you apply water pressure to an RO unit, it will produce pure water, so the easiest way to start and stop one is to turn a water valve on or off. For the countertop unit, this is the only means of control you have. Our under-counter drinking water system includes an automatic shutoff valve that senses system pressure. For RO systems that are fed by a pump, we offer a control package that can turn the system on and off when necessary to keep your tank full without overflowing. There are many options available to fit your specific needs. |
| A Word About Semi-Permeable Membranes The semi-permeable membranes are the heart  of the reverse osmosis system, and they are typically installed in a cylindrical housing that is similar to a filter canister. As with other filters, the material they are made of makes a big difference in their performance and longevity. We sell high-quality, thin-film membranes made by Filmtec, a division of Dow Chemical. We have several sizes available, with flow rates of 8 to 75 gallons per day. If the feed water is pre-filtered to remove sediment and chlorine, the membranes will last a long time. They do eventually need to be replaced, so we sell replacement membrane units, and they are easy to install. |
|
To shop for RO systems and components that you can use to process all of the water you use, go to Whole RV RO Systems. To shop for systems and components to provide RO on just your potable water, go to Drinking Water RO Systems. |
Previous: Water Softening and Mineral Removal Next:UV Light Sterilization
