Water Management - Creating a System for a Car Wash
By Dwight Royal
When most operators think of a water management system (WMS) for their car wash, they think of holding tanks, some pumps, an RO/softener, and reclaim unit. These are no doubt key components that the WMS needs in order to operate. However, there is much more that must be considered when setting up a viable system that manages your most precious asset, water. You need to recognize and understand the types of water that are available to you and where to best use them. The three types of water are fresh water, spot-free water, and reclaim water.
Each wash and wash owner’s budget and expectations are different when it comes to managing water. Understanding these three types of water and what you can expect from them will help you make an informed decision to meet your budget, fulfill your expectations, and provide you with the best WMS for your specific needs.
Most people do not realize that their fresh water is the steppingstone on which the whole system is built. Fresh water is used to make spot-free water, reverse osmosis (RO) reject water, and finally reclaim water. Therefore, the quality of this water will affect the whole system. Although our goal is to add as little of this water as possible, it is a necessary evil. This being said, it is imperative to know what you are working with at the beginning in order maximize the efficiency of your WMS. It is always best to know the makeup of the water. Get a water analysis. If you are utilizing a municipal feed, you can typically get this from your water provider. If you are using other sources of water, it is a good idea to have this done by a professional. We suggest that you check your water makeup every year because it can change.
Different additives, hardness levels, and pH can react with wash chemicals and create an adverse effect. Not to mention, hard water and chlorine will destroy RO membranes. Once the water has been tested, it can then be determined what type of treatment must be used to make the water work best for the site. For example, if using a well to operate the wash, one must take into consideration the quality of water being provided. Many wells will require some pre treatment of the water to make it a viable choice for use in the wash process. Some wells provide such low quality water that it is not feasible to use for the production of spot-free water without treatment. Spot-free reject water is not all the same. It will vary from site to site.
So what may work at one site for pretreatment may be ineffective at another site.
Provide your RO manufacturer with the water analysis data and they can suggest the best pre-treatment for your site (see a typical analysis on page 18).
Pre-treating your fresh water will not only give you good results with the RO unit, it will ensure that all of the other waters are at their best.
SPOT-FREE AND RO REJECT WATER
Now that we have the best possible base with our fresh water, it is time to discuss spot-free water and RO reject water. Spot-free water is the purest water in the house. Due to the lack of impurities in this water, it is hungry for any outside minerals and chemicals. This is why it is used as a final rinse. The spot-free water will absorb these elements and rinse them away eliminating any spotting that may show up on the car. Due to these properties, it is also good for mixing chemicals. Even though this water can be used in final rinse and chemical mixing, it is still a small portion of the water needed in a good WMS. A key component to this part of the WMS is how much RO water you need. You must keep in mind that for every gallon of RO water, there is approximately one gallon of RO reject water that should be captured and used before it is retired to the reclaim pit. All equipment manufacturers can answer this question. It’s as easy as counting nozzles and the time the car is under the application.
Flow and Pressure
One thing people never consider is how much fresh water they have available. And by this I mean flow and pressure. Within your WMS, you must make certain that you have the correct amount of water and pressure available to operate all the equipment in the wash. It is often forgotten that the spot-free system will have to operate when the wash is running at full volume. You will have pressure drops across any pre-treatment process, as well as the RO itself. Many sites that use larger RO systems do not take into account the water pressure and volume required to run the spot-free system during peak hours. This starves the spot-free system, which lowers its output and prematurely ages the system due to low flow and pressure. A few spot-free manufacturers install low-flow and pressure protection on their units for this specific reason. This makes a big difference in whether you can use a big RO and smaller holding tanks, or a smaller unit with larger holding tanks. It is very important to realize what your working flow and pressure are in your fresh-water feed. Knowing this can help you size your units and add booster systems if needed.
The key to good water management is using the many products available to ensure that there is always enough water to operate the equipment. We can do this by using reclaim water in many of the high-pressure functions of the wash. This will reduce the amount of source water needed in the wash process. Generally reclaim water can easily be used in at least 50 percent of most wash processes. Using a reclaim system can go a long way towards relieving flow and pressure issues that arise in most wash sites. Spot-free reject water may also be another source of water that can be used in the wash process. By and large it is used in high-pressure functions too. If you test your fresh water and pre-treat it properly, there is a good chance that the quality may be good enough that you can consider it for chemical mixing. In many cases, even with proper fresh water pre-treatment, the water quality of the spot-free reject may not be good enough to use as a direct fresh-water replacement without causing some issues. In these cases, it is better to treat it as reclaim water instead of fresh water when deciding where to use it in the wash process.
Reclaim water is the sum of all of the waters previously mentioned and everything else that you dump into it. Now you can see why it is so important to have good water going in. If you don’t, you are fighting hardness, pH, and all of the various biologicals, elements, and chemicals that are trying to break down. The less junk to treat, the easier it will be for the reclaim system to perform. Some operators see a need to take the reclaim water and turn it back into fresh water and even RO water. Can this be done? Yes, but, you must carefully weigh the expense, time, and effort required to accomplish this. An operator who goes this route must understand that the whole game changes and they are not typically receptive to this idea. The old adage of “biting off more than you can chew” comes to mind. Things like constant monitoring, minimal use of chemicals, and extra maintenance become a must. Most do not find it economically feasible, but it is good to know that it can be done if it becomes a necessity.
Another area of water management that is often overlooked is the plumbing and placement of the reclaim reservoir in the initial planning. Most reclaim units use centrifugal pumps that draw the water from an underground tank system, filters it, and send it to the wash. The tanks need to be situated so they are as close as two-inch or three-inch plumbing is specified for a reason.possible to the equipment that they will be feeding. Pump manufacturers suggest 50 feet or less of plumbing to connect the tank system to the reclaim system. This plumbing should be as direct as possible with the fewest elbows and turns possible. This will give the pump(s) the best opportunity to work as designed. If the suction line for the system gets much longer, the pump will struggle to pull the water from the reservoir properly. The pump may have to operate under a heavy vacuum and it may be near impossible to prime the pumps upon restart. Also pay attention to the manufacturer’s pipe size recommendations. There is a reason that two-inch or three-inch plumbing is called for in set up. These sizes are what are required for the volume of water that the system needs to operate. Not following these suggestions will put you behind the eight ball before you start up the wash.
To the uninformed, the first reaction to the problem is that the reclaim system is faulty when in reality faulty plumbing is the culprit. It is of the utmost importance that care is taken installing the reservoir tanks and the plumbing connecting them to the reclaim system. If this step is overlooked or done incorrectly, it won’t matter which system you put in, because none will perform as advertised or they may never work at all.
A water management system is the lifeblood of the car wash. Understand your various waters and use them wisely. Do not overuse fresh water and underuse reclaim water. Make sure you start with the best quality water possible and that you have the proper delivery systems for these waters. Understand the system and always plan for future needs. A well thought out and managed WMS will be the best preventative maintenance you will ever do.
Dwight Royal is CEO, vice president of operations at Con-Serv Manufacturing. You can visit the company on the web at www.con-servwater.com.