Lipstick On A Pig
Sometimes, when a company installs a commercial reverse osmosis system, they start with a system that really doesn’t fit their needs for a variety of reasons. A lot of that is they simply don’t know what they don’t know.
Among those reasons are the following:
- They may have thought they needed (as an example), 500 Gallons Per Day (GPD), so they bought a 500 GPD RO system. They may have failed to understand that a system is rated at 500 GPD IF it runs 24/7 (not a good idea), and that rating is at 77 degree F water temperature and 60 PSI. For every degree below 77 degrees, you lose about 2% of output, so if your water temperature is 52 degrees, you would lose approximately 50% . That 500 GPD RO system is actually a 250 GPD system… if it runs 24 hours a day.
- When they bought the system, they had no idea how much their business would grow and so they did not purchase a system that was capable of handling any future expansion.
- They may have purchased a system from a company who really doesn’t specialize in commercial reverse osmosis systems and therefore, they may not really have the appropriate system.
- Over the years they may have added components because different companies had their own opinions as to how best to address a problem.
I have been involved in the sales, service and installation of thousands of reverse osmosis systems over the past 40 years and have to admit that I have made every mistake in the book … and some that weren’t even in the book. That, in itself, makes me supremely qualified to address this issue, but my years of training and experience helps even more.
“You can’t put lipstick on a pig” is a quotation I use frequently. Sometimes, a system is so poorly designed and undersized that you will spend a lot more to upgrade/repair a system to produce 85% of what you might need, than you would if you just replaced a system.
I recently looked at a system that was evidently installed “piecemeal” and after considering their needs, we recommended they “blow it up” and start over. They had a 500 GPD reverse osmosis system and (2) 200-300 GPD systems. They needed 1.5 GPM for many days straight and in the real world, their system would supply less than half of that flow rate. They wondered why they had a problem.
They had filters ahead of the reverse osmosis system and the whole thing looked like it had been built as a “hey, let’s try this” project. The solution was simple, just like with any reverse osmosis system.
Here are the Ten Commandments for Commercial Reverse Osmosis Sizing and Application:
- You start with proper pre-treatment(no matter how good the reverse osmosis system is, it won’t work very long or very efficiently to provide high quality water without proper pre-treatment). Proper pre-treatment includes (but is not limited to) the following:
- Iron/Sulfur/Manganese Removal for Well Water;
- Chlorine Removal for City Water;
- Water Softening or Anti-Scalant Injection (this is the preferred method, even better than water softening and it requires no salt; or
- Disinfection such as ultraviolet or ozone for bacteria removal.
- You size a reverse osmosis system to the highest daily capacity needed. In this case, they needed about 2,200 Gallons per day;
- Ideally, you don’t want the reverse osmosis system to have to run 24 hours a day to produce the daily total gallons needed. It is best if you can produce that amount of water in 8 hours, meaning that the RO system will only run 1/3 of the time, which is 8 hours;
- You can push the envelope and try to produce it in 12 hours, meaning that the system has to run ½ the time. In the aforementioned case they would need a 5,000 GPD system to have it run approximately half the time or a 7,000 GPD system to have it run only a third of the time;
- The advantages of having a system run half or one-third of the time are numerous and include dramatically increasing the system's longevity while greatly reducing the energy consumption. We have systems that were engineered to run 1/3 of the time that have been in for over 11 years with no pump or motor replacements and these systems could show a 40-50% increase in energy savings;
- Consider “Green Options” which are reverse osmosis systems that recover 75% of the water used through a Computer Controller, Permeate Flush, Ultra Low Energy Membranes and Concentrate Recycle. Typically our standard systems will recover 50% of the feed water. What this means is for every "good" gallon that is produced one gallon of concentrated water is wasted to the drain. In a 75% recovery system there will be 1/2 gallon wasted to the drain for every 1 gallon of "good" water produced.
- Is Re-mineralization necessary?After the reverse osmosis system, you may want to re-mineralize the water if it is used in a foodservice application. If all the water needs to be re-mineralized, then it is best to re-mineralize it as the water flows from the RO system to the storage tank because the flow is always the same and much lower than the flow after the system.
- This usually means that you can use much smaller re-mineralization systems, like cartridges instead of large tanks.
- If you re-mineralize AFTER the RO water storage tank, you will have to size the tank to your highest flow rate which could be 5-10 times greater than what the RO produces. It is much more precise to re-mineralize BEFORE the storage tank.
- Re-mineralization is an absolute necessity if the water is going to be distributed in copper pipes (especially in a home with copper plumbing). Ideally, the point of where the water is properly re-mineralized is at 30 to 40 PPM of TDS (Total Dissolved Solids).
- Typically a media called Calcite (which is calcium carbonate flakes) is used to raise the pH and mineral content. This can be in the form of a cartridge or a tank containing Calcite. Whether you re-mineralize before the tank or after the tank depends upon whether you want all of the water to be re-mineralized or just part of the water.
- The cheapest system you can buy may actually prove to be the most expensive.Here’s why:
- While our “Green” systems recover 75% of the water, there are many competitors systems that recover only 15%.
- Let me put that in perspective. That means that to make 2,000 gallons, you would waste over 12,000 gallons! Not only is that wasteful, but it is also expensive if you have to pay for your water and/or the electricity to pump it.
- Many systems operate at 150 to 200 PSI while most of our systems operate at 80 to 100 PSI. Think about that: Fittings, tubing, pumps, flow meters, gauges, needle valves and motors have a lot more stress exerted upon them at 200 PSI than at 100 PSI. TWICE AS MUCH! It dramatically affects the system's longevity. RO systems work better and last longer at lower pressures, AND lower pressures means less energy.
- So you dramatically increase the life expectancy of the system and you save up to 50% on energy in the process, making the system that might cost $2,000.00 more, the least expensive system in the long run.
- Do you need a bladder or atmospheric tank?Depending upon what you plan to do with the water and how much you require, will determine what type of tank you need. In foodservice operations, especially where there may be 20-400 gallons per day usage and where extremely low TDS is not required, a bladder type tank is simple, easy and reliable. However, if you are using hundreds or thousands of gallons a day, or if you are using reverse osmosis as pre-treatment for de-ionization (DI), then you would absolutely not want to use a bladder-type pressure tank.
- A bladder pressure tank has pressure behind the bladder. This is what causes the water to be expelled from the tank when it is called-for at any point-of-use.
- As the tank fills, the back pressure on the RO system increases, causing the RO to work harder to push water through the membranes. This results in less effective reverse osmosis treatment and higher TDS in the permeate water. This also causes the recovery rate to drop. Because there is back pressure on the membrane more water is wasted to the drain as the pressure in the tank increases.
- Typically, water from a bladder tank will have a TDS level two to three times higher than a comparable RO discharging into an atmospheric tank.
- The back pressure is what makes all the difference. If you were to de-ionize water that was not treated by reverse osmosis first, the cost can be 20 to 50 cents a gallon. With an atmospheric tank, the cost can be 2 to 3 cents per gallon and with a bladder tank, the cost can be 4 to 10 cents a gallon. If you use 4,000 gallons a day, that’s a big deal! In a DI system the the mixed bed media used to treat the water is the main consumable. Water not treated with RO will have a much higher TDS which causes the DI media to remove the TDS and not the RO. This can be very expensive in the long run.
- An atmospheric tank allows the RO to fill the tank with no back pressure. This allows the RO to work at a consistent flow rate and TDS. An atmospheric tank requires a float switch to shut the RO system off when the tank is full and to turn the RO system on when the tank level drops. A re-pressurization pump is required to re-pressurize the water from the atmospheric tank. This ensures adequate flow and pressure at each point of use.
- Make sure you have a tank that is adequate for your application.The worst possible situation is to run out of water. A reverse osmosis system only makes water at a certain pace, depending upon its’ size. If you have a coffee shop that requires 40 gallons of water by 9AM and you only have a tank that holds 10 gallons, you will run out of water, unless you have a RO that can make water that fast or unless you get a bigger tank.
- Sometimes, doorways are the determining factor. If you have a 32” door opening, then you can only get a 31” tank through it and sometimes doors that are sold as 32" doors only have a raw opening of 30 1/2". If it is an atmospheric tank, the largest one you can get through the door would be a 265 gallon tank. What if it was determined that you needed 500 gallons of storage, but only had a door opening to accommodate a 265 gallon tank? Simple: manifold two tanks together. Sometimes we have to connect 5 or 6 tanks together in situations like that.
- Typically, atmospheric tanks range from 65 gallons to 2,000 gallons, although larger tanks are available. You are usually better off if you use (2) 2,000 gallon tanks instead of (1) 4,000 gallon tank.
- If you use an atmospheric tank, make sure you have adequate pumping capacity. This means that if your needs are 20 GPM, you wouldn’t want to put in a 15 GPM pump. Sounds simple, but we see this problem all the time. Frequently we recommend a Grundfos MQ3-45 that delivers up to 22 GPM or whatever you need in-between without the use of an additional bladder tank. Additionally, if your application is in a severe environment, like extreme heat, you may need a special heavy-duty pump able to withstand extreme temperatures. In foundries and places where the ambient air can be well over 100 degrees F, it may be necessary to put a chilling loop in the storage tank. If there is a recirculation line needed it is important to make sure the pump is rated for continuous duty.
- Determine if you need disinfection and what type is needed.This is especially important if you have an atmospheric tank. Airborne bacteria or other micro-organisms can get into the tank, and unless it is solely for manufacturing use, it would be a good idea to have an ultraviolet light (UV) after the pump. This assures that the bacteria is being destroyed prior to distribution.
- While UV is generally the best choice, in some cases ozone is a better choice. This is especially true if the environmental conditions promote algae growth inside the opaque tank.
- In high purity applications (we will discuss that next), the water frequently is circulated in a loop where a small amount of water is diverted back to the tank and therefore back through the UV over and over.
- In water bottling applications, an ozone generator is essential as the ozone will still be present in the water as it is bottled which ensures bacteria removal. If you ever have opened a bottle of Aquafina (which is RO water), you will hear a little “Whoosh” which is the remainder of the ozone bubbles escaping.
- Sometimes, timers are put on small ozone systems which are ran once a day or once a week for a few hours to just sanitize the water and prevent algae growth.
- Do you need high purity water?Laboratories and other manufacturing facilities frequently need high-purity water. The purity of the water is typically referred in terms of megohm or microsiemens. 18.2 megohm is considered the highest purity (that would be 0.055 microsiemens). Most applications need water quality that is 500,000 ohms, 1 megohm or 2 megohm.
- Traditionally, companies have utilized tanks that have a mixture of cation and anion resin to deliver ultra high purity water. However, a properly-sized reverse osmosis system with good pre-treatment will often produce water quality so low that DI cartridges can be the most cost effective method of de-ionizing water.
- Frequently, we install two to eight 4-1/2” x 20” DI Cartridges. Assuming RO quality of 5 PPM of TDS, each of those cartridges will de-ionize about 7,000 gallons. If the RO quality is 2-3, that doubles the amount of water that can be treated by the cartridge. If you feed raw water into a DI cartridge the TDS of the water can be 400 ppm. So that same cartridge can only produce 88 gallons before it is spent.
- You will need to have proper instrumentation, such as a TDS meter, conductivity monitor or a quality light. These quality lights are available in 500,000 ohm, 1 megohm and 2 megohm sizes. The light glows green as long as the water quality is above the threshold and turns red when the water quality falls below that threshold.
- Typically, we would install a light between two cartridges or banks of cartridges, so that when it turns red, the second bank is still delivering the requisite water quality.
A properly-sized RO system should work effectively for 15 to 20 years. We have a large laboratory that operates 24/7/365 and has a system that was installed over 11 years ago. The membranes have been changed twice and the pump and motors are still working fine. The secret? Redundancy! They have two reverse osmosis systems, two pumps and two banks of DI cartridges. Additionally, they have proper pre-treatment.
On the other hand, we talk to other companies who replace motors every few months and have nightmares with their systems. The devil is in the details. There is no one big secret – it’s a hundred little things. That’s where our experience comes into play. At US Water, we have over 120 years of combined experience with our Certified Water Specialists. We also provide technical service from 8 am to 11 pm, 365 days a year. Water is not considered much until it is unavailable. Do you want buy a system that is only supported during normal business hours? That would be fine if they could guarantee you will only have a problem from 8-5. That is just not possible. US Water understands the importance of water to life and a live person will answer your call when you have a problem.....even on Christmas. Try to get that guarantee from another company. We aren't selling shoes. We are selling well being. We take our job/profession serious and we are dedicated to provide top notch service and equipment. Please keep these things in mind when you are looking for a water treatment system.