As with fingerprints, no two water supplies are exactly the same and water use requirements differ. Water’s chemistry dictates the process for making that water aesthetically pleasing, palatable, and suitable for its intended use. Applying water conditioning correctly requires basic knowledge of water and system design. Invariably, if you blindly trust others to size and apply water conditioning without asking questions and verifying information, you will quickly discover that bad water makes for unpleasant times.
Whether contracting for the entire project or simply providing design information, your reputation is always on the line. It is important to be associated with quality work. The information offered in this article provides basic knowledge for applying engineering, sound science, and common sense to the treatment and conditioning of water.
Some people believe that conditioning water is as simple as walking into the nearest mega-mart and picking out a preassembled conditioner. They are wrong. Too often, the information provided in the specification book is vague, encrypted, and/or written to limit competition. Make it a habit to question the plan provider (manufacturer) and enlist the help of a trusted water professional before accepting future responsibility for specified water processing equipment.
When done correctly, water conditioning applications are all custom designs, taking into account the water analysis, the end-user’s flow and usage requirements, and future service functions. Do your homework before installing any water conditioning equipment.
The “Find a Water Professional” feature on the Water Quality Association (WQA) Web site (www.wqa.org) can help you locate knowledgeable personnel in this area. As WQA represents the full spectrum of the point-of-entry/point-of-use water conditioning industry - residential, commercial, and industrial - be sure that the company you select has experience in your specific type of application. WQA also has a professional certification program, so the company listings will include all the certified personnel on staff.
System Design ReviewAfter receiving the results of a water analysis, the design agent must analyze the results and determine the usage needs, required pressure, and flow rates (both the continuous and the peak). Each of the aforementioned design concerns requires careful attention before finalizing the specifications for a water conditioning system.
Here is a list of questions to ask during the review process:
Without answers to these questions, you’re putting your success at risk.
Basic InformationNo matter how large or small the project, they all have common denominators. A project manager must review past learning and approach each system in a similar manner. Here are some items to consider before starting any water conditioning project:
Each piece of equipment must function properly within the system. Look for problematic flow patterns and/or questionable materials.
Many systems have outside influences that may affect operation. Look for large water-using appliances or machinery that may steal feed water and pressure from the water conditioner during its recycling operations.
Identify the water flow dynamics. Will the system receive extreme variations in flows (i.e., 2 gpm to 100 gpm)?
Keep to the engineer’s specified equipment sizing. Do Not accept system size reduction based on information from a vendor’s sales staff without engineering approval!
Every project has different water and different water quality standards. Double-check that the equipment specified is appropriate for the water condition. Never assume the information provided is correct – verify before moving forward. All systems eventually require service and you should plan for it.
Key FactorsWater Quality
Water quality parameters determine the type of equipment needed for each job. It is essential to inquire about the water’s intended use. Never assume that the end user is an expert in water. The quality specification requested may not be the quality needed.
Real World Example: A customer asked for a reverse osmosis system with a deionizer to purify water. A simple question about the system’s intended use showed it to be water for a testing laboratory. After reviewing the specifications, it became evident that a crucial piece of equipment was missing from the system. The specifications did not call for any form of sterilization. Purified water is susceptible to microbiological contamination. For laboratory use, purified water must flow through an ultraviolet sterilizer or other type of sterilization just prior to use.
Asking a simple question and reviewing specifications helped to avoid system failure.
Many bid requests for water conditioners simply state a gallon per minute flow rate. This is not enough information. It is imperative to know where the water is going and how much pressure is required when it gets there. If the water conditioner is located hundreds of feet from its discharge destination, pressure loss due to friction may be a problem. Pressure loss can become a major problem.
The WQA publishes a number of basic texts on water conditioning. Water Treatment Fundamentals and Water Processing: Residential, Commercial, Light-Industrial both offer quality explanations of water analysis, contaminants, and treatment options.
Flow Rate. Peak flow rates can be very misleading. It is important to know that a water softener can sustain an intermittent peak of 1-1/2 times its continuous design rating. It is also very important to know that iron filtration equipment cannot handle flow rates that exceed their design parameters. Iron filters tend to trap ferric iron in the top third of their media bed. When water passes through the filter at rates higher than prescribed, the trapped iron breaks through the filter medium into the effluent lines. This phenomenon, referred to as “dumping,” results in iron-fouled water. When sizing either a water softener or an iron filter, the designing agent must know the peak flow rate.
The continuous flow rate and usage are the most important factors in sizing. The continuous flow rate is the gallons per minute at which the system processes water under normal operating conditions. Usage is the gallons required over a given time period or process. A system using 30 gpm for two hours will be significantly smaller than a system using 30 gpm 24 hours per day. Without knowing how the system is to function, correct sizing is not possible.
Another crucial issue in softener sizing, based on flow rate and usage, is brining time. Brine saturation requires 4 to 6 hours, depending on water temperature, in a normal grid-style brine tank. Alternating softeners cannot cycle faster than the brine is saturated.
Low Flow. Low flow and low pressure are also potentially problematic conditions that could arise, although many water system designers do not consider low flow. Line pressure pushes water, not pulls it through, conditioning media at designed flow rate. If water moves too slowly through media, it will take the course of least resistance – water always takes the course of least resistance. This causes the water to channel through the media and/or flow between the inner tank lining and the media bed – referred to as “wall effect.” Water that does not pass through the media is not conditioned. This results in poor water quality. Low flow issues can be rectified by installing multiple smaller systems and spreading the flow between them. New generation controls allow multiple systems to progressively come on and off line based on flow rates, making multiple tank systems a popular choice in many applications.
Venturi assemblies and regeneration cycles require a minimum feed line pressure, usually greater than 20 psi. Macro/micro filters and membranes also require a certain minimum flow rate and pressure. Without the required flow rate and pressure, water will not pass properly through the filtering devices. Remember to differentiate between static pressure (pressure when water is not moving) and working pressure (pressure at a given flow rate). In a case of low pressure and flow, consider increasing the size of the water supply line and/or adding a booster pump.
Knowing exactly what is in the water determines what devices to use to accomplish the desired conditioning. Never trust a water analysis from a third party unless the testing laboratory is approved by the local governing body, and do not be shy about asking for a second opinion. The water analysis must be correct. If a water analysis is wrong, the type and size of the system may be wrong.
The concentration of mineral salts in the water, multiplied by the water volume used over time, determines the physical size and type of most water conditioning equipment. The slightest error can cause total system failure. It is unfeasible to process 200 gallons of water per day with a system only capable of processing 100 gallons of water per day.
Always review the installation site. A matter as simple as the size of the door can become a big problem. Equipment may be designed that will not fit through the door. Discuss electrical requirements. Double check voltages and inquire about other equipment serviced by the electrical service. Computerized equipment cannot tolerate voltage variations.
Review the water conditioner’s prescribed supply pressure and volume. Always ask what else the water line supplying the water conditioners supplies. If other devices share the same supply line, identify them and examine how they may affect this system. A designer must know the system’s footprint and the elements that surround it. Document all aspects of the installation for reference. Solving a service issue over the phone by referring to job notes may avoid an on-site service call.