Salt tank refill function—During this cycle, a controlled stream of water flows into the salt tank to make up a saturated brine solution for the next regeneration. The salt tank refill time should be based on the fact that 1 gallon of fresh water dissolves approximately 3 lbs (1 L dissolves 360 g) of salt.

For example, assume you have specified the size of the softener to be a 16” × 65” tank with 4.6 ft3 (130 L) of resin. You decide to choose the medium salt setting of 9 lbs/ft3 (150 g/L), referring to the accompanying design chart. The amount of salt required is 42.9 lbs (19.5 kg) and the amount of salt brine containing this is 15.9 gallons (60 L) saturated brine. The control valve manual says that the injector for a 16” diameter tank educts the saturated salt brine at a rate of 0.7 gpm (2.6 L/min). Therefore, the downflow brine time required is 22.7 minutes.

At the medium salt dose, each cubic foot of resin has a capacity of 26,000 grains (each liter of resin can remove 0.060 kg hardness). If you are limited to only one regeneration per day (as with a timer-controlled valve), then a volume of 260,000/26,000 = 10 ft3 (about 283 L) of resin is required. This typically requires a 24” × 72” tank.

Fast rinse function—The fast rinse flows through the backwash flow control so its flow rate is the same. For most applications, the fast rinse time should be 6 to 12 minutes depending on the volume of resin and the application. For instance, most domestic and commercial applications can use the lower range while reverse osmosis (RO) and deionization (DI) pretreatment and boiler feed and industrial process applications should have longer rinse times.

Bear in mind, the 16” tank with 3 ft3 of resin produce a bed depth of just under 26 inches (65 cm), which creates the 24” minimum resin bed depth requirement of the resin manufacturer. Also be aware that if the service flow is too low, the water can “channel” through the resin bed only using a fraction of the resin’s capacity. Use a lower flow limit of no less than 1 gpm/ft3 (8 m3/h/m3).

No, in fact, a water softener can help extend the life of the RO membrane. Calcium and magnesium (limescale) are two of the hardest minerals for the RO membrane to remove, and sodium (added to the water by the softener) is much easier on the membrane as it rejects 98% of all sodium in the water.

While both RO units and distillers effectively reduce the "dissolved solids" content of water, the processes are quite different. RO filters water through a very tight semi-permeable membrane, while a distiller is like a big teakettle in that it boils water, catches the steam, condenses it, and captures the resulting water. Most impurities are left behind in the boiling chamber. Both rely heavily on carbon filtration for chemical removal. It's worth mentioning that cheap distillers often have little or no carbon filtration and are not as effective.

Consider multiple regenerations—It’s important to understand that multiple daily softener regenerations can reduce system size and cost. If the application is suited for multiple regenerations per day [you need an alternating multiple-tank system or a cistern (reservoir) that can supply treated water for the customer during regeneration], then a more cost effective softener system can be designed. This is an especially good strategy where cisterns are commonly used to store treated water before the points of use (as in Latin America). Consider using three regenerations per day (roughly every eight hours for continuous flow) for the example above. Then, to meet the capacity requirement, only one-third the amount of resin is required or 3 ft3 (85 L) for this example.

1. The amount of salt required to regenerate the resin bed (refer to accompanying design chart) 2. The flow rate that the injector educts brine into the resin bed (consult the control valve manual for the this specification)

To determine the volume of resin by volume of water treated and hardness, start by estimating the maximum total grains (or kilograms) of hardness that must be removed each day.

Low limit salt dosage—6 lbs salt/ft3 (about 100 g salt/L) resin gives hardness removal capacity of approximately 21,000 grains/ft3—48 grams of hardness as calcium carbonate (CaCO3) per liter [g(CaCO3)/L] or 0.96 equivalents per liter (eq/L). Medium salt dosage—9 lbs salt/ft3 (about 150 g salt/L) resin gives hardness removal capacity of approximately 26,000 grains/ft3—60 g(CaCO3)/L or 1.19 eq/L. High salt dosage—12 lbs/ft3 (about 200 g salt/L) resin gives hardness removal capacity of approximately 29,000 grains/ft3—66 g(CaCO3)/L or 1.33 eq/L). Maximum limit salt dosage—15 lbs salt/ft3 (about 250 g salt/L) resin gives hardness removal capacity of approximately 31,000 grains/ft3—71 g(CaCO3)/L or 1.42 eq/L.

The backwash segment of the regeneration removes dirt and debris from the resin and is determined by two things: a. Diameter of the tank—Refer to the accompanying design chart (see Table 1) for cross section area. b. Temperature of the water—This determines the water viscosity as an inverse relationship. As water temperature decreases, it becomes more viscous (thicker) and will cause greater expansion of the resin bed during backwash.

1. A twin-metered alternating softener using 16” tanks with 3 ft3 of resin (each regenerates three times every two days—about every 16 hours) where continuous direct flow of softened water is required. 2. A single-metered softener using a 16” tank with 3 ft3 of resin (which regenerates three times per day) where a cistern of treated water is available to supply the customer with a continuous supply of softened water.

RO units remove about 95% of the mineral content, but the mineral issue is probably the most controversial question in drinking water purification. Experts on both sides of the issue speak convincingly. As long as water is palatable, it's within the body's acceptable range. The main issue with water is chemicals, not minerals. Whether water contains 30 or 3 parts per million calcium is not nearly as significant as the difference between 0.5 and 5 parts per million chloroform.

While the RO membrane itself does not remove chlorine, it doesn't have to. A couple of high-quality carbon filters will do that job. In fact, if the first carbon filter didn't remove all the chlorine, the membrane would get eaten alive in no time.

Slow rinse function—As stated above, the slow rinse cycle is actually an extension of the “downflow brine/slow rinse” function”—but with no salt brine being educted. The continued water flow through the injector provides this slow rinse. The recommended guideline is to have the entire downflow brine and slow rinse cycle be three times as long as the brine cycle.

Water softener flow rateper square foot

For example, assume the service flow is 15 gpm—56.8 liters per minute (L/min). Based on the guideline above, the recommended resin volume is 15 gpm/5 gpm/ft3 = 3 ft3. The cross section area guideline recommends a resin bed area of 15 gpm/10 gpm/ft2 = 1.5 ft2, which corresponds to a 16-inch (“) tank (1.4 ft2) and a resin volume of 4.6 ft3. You have the choice of using a 16” tank with 3 ft3 (84.9 L) or use a normal resin volume of 4.6 ft3 (130.2 L) for added capacity to meet future expansion or increase in hardness.

Notice that even though the salt dosage more than doubles, the hardness removal capacity doesn’t. The higher the salt dosage, the lower the salt efficiency.

Backwash function—Eight to 15 minutes is recommended depending on the amount of particulate matter (sediment) in the water supply and water scarcity. If iron is present, use the upper range. The backwash flow is regulated by a control orifice that restricts the drain flow to the specified flow rate.

All RO membranes produce similar, highly purified water. However, not all systems offer the same features. For example: The FMRO5-MT model is perfect for city water applications. This unit has five stages, meaning the water passes through a 5-micron sediment polypropylene prefilter, then two solid extruded carbon block cartridges for chlorine removal, then the RO membrane to remove the smallest of contaminants, and finally another carbon filter to polish the taste. The FMRO4G-ERP has water conservation in mind with a high-efficiency design. This model produces more water in a shorter period of time, with less water going to the drain than a traditional 50 gpd RO. This is due to the non-electric permeate pump that utilizes the drain flow to reduce the backpressure from the storage tank allowing a more consistent working pressure across the membrane. The WQC4RO13 model is designed for the consumer that would like a low maintenance premium RO. This model is designed with a designer water-dispensing faucet, low profile polypropylene storage tank, and manifold filter heads that are able to pivot 180 degrees with built-in shut off valves to make filter replacements as easy as a 1/4 twist of the filter.

Water softenersize calculator

The injector creates suction for the salt solution. During regeneration, water flows through the injector venturi and creates a vacuum to pull salt brine from the salt tank. The injector is primarily determined by the diameter of the tank. The proper injector selection is found in the manual of the control valve you’re using.

The softener design guidelines outlined in this article and accompanying chart are intended to provide a base of information for general purpose softening applications such as domestic use, commercial and institutional washing and laundry, non-critical industrial processes, low pressure boilers, cooling towers, and RO and DI pretreatment. More demanding applications like high-pressure boilers, medical autoclaves and water sources containing problem contaminants like iron and manganese require additional special considerations. Thus, you should consult your other professional sources for specific application guidelines.

Downflow brine function—It’s important to understand that the downflow brine function is only the first part of the complete “downflow brine/slow rinse” task. The control valve remains in the same position for the entire function. During this first part, saturated salt brine solution is sucked (“educted” or “drawn”) from the brine tank, mixes with the venturi injector water stream (to a concentration of about 10 to 13 percent), and flows through the resin bed to regenerate it (or chemically displace the hardness removed). The NaCl content of saturated brine is 2.7 lbs/gallon (300 g/L). The brine function time is determined by:

To put it simply, the water in modern home units is driven by normal city water pressure and flows through a sediment pre-filter which removes any dirt and small particles that are in the water. Next, a carbon pre-filter removes organic contaminants, including chlorine and its by-products. It then enters the reverse osmosis membrane-- a very tight, sheet-like filter-- which allows water to pass but rejects dissolved solids and impurities such as sodium, lead, and arsenic. Some of the water entering the unit is used to cleanse the membrane surface and flows to the kitchen drainpipes. The purified water is stored in a small storage tank until it is needed. When the faucet mounted on the sink is opened, the purified water is forced through another carbon filter, which gives it a final polish and from there to the faucet. Of course, there is more to it than this simplified description as flow control devices, check valves, and automatic shutoff devices that stop the inflow of water when the storage tank is full all play an essential role in RO, but we'll save you the time for now.

Water softener flow ratechart

For example, consider the instance above. The brine time is approximately 23 minutes. The total brine and slow rinse cycle should be 3 × 23 minutes = 69 minutes.

But let’s check if this reduced volume of resin can meet the service flow rate requirement of 15 gpm. Referring to “Resin volume vs. service flow rate” section, 15 gpm (57 L/min or 1 pm) service flow requires at least 3 ft3 of resin. The flow rate is compatible with the resin volume required for the hardness capacity. Now, instead of a 24” tank with 9 ft3 of resin, the system can be reduced to:

What sizewater softenerfor family of 4

The resin capacity for hardness, or amount of hardness that can be removed by cation resin, depends on how much salt is used (dosage) to regenerate each liter or cubic foot of cation resin. The normal range is 6 pounds of salt per cubic foot (lbs salt/ft3 or lbs/ft3) of resin—about 100 grams salt per liter (g salt/L or g/L) of resin—to 15 lbs salt/ft3 (about 240 g salt/L) for standard mesh resin. The capacity for each salt dosage can be approximated in the following:

Virtually forever if you service it regularly and replace parts that wear out, like the storage tank and the faucet. Typical membrane life is about 2 to 5 years, depending on the nature of the water that it's processing.

Bear in mind, the above capacity values are only approximate. Consult the specifications from your resin supplier for more accurate capacity specifications.

The regeneration cycle consists of a sequence of functions that correspond to control valve “positions.” For most customers who only have to remove hardness, the following sequence of regeneration functions is recommended:

No, they run on water pressure. You only need electricity if you add an electric pressure-boost pump or an ultraviolet lamp. Standard units have neither.

Reverse osmosis, often referred to as RO, is an advanced water purification method that was initially developed by the U.S. Navy to produce drinking water from seawater for submarine crews. It is a membrane filtration technology that works by forcing water under pressure through the very tiny pores of a semi-permeable membrane. Modern RO units for the home combine membrane technology with carbon and mechanical filtration to produce highly purified, great-tasting water.

The volume of cation resin is generally determined by four things: a. The service flow rate, b. Hardness of the water, c. The volume of water to be treated, and d. The number of times a day the softener can be regenerated (i.e., valves with flow meters allow multiple regeneration per day). Usually three times is the practical maximum number of regenerations per day because: • It typically takes up to two hours for regeneration, and • It takes up to three hours (depending on temperature) to make a saturated salt solution in the brine tank.

Water softenercapacity

For example, consider the situation above. The amount of salt required for the medium salt setting is 42.9 lbs. (19.5 kg). The manual says the salt tank refill flow rate is 0.5 gpm (2 L/min). The volume of water required to dissolve 42.9 lbs of salt is therefore 14.3 gallons (54.1 L) and the time is 28.6 minutes.

The first objective is to select a valve that offers acceptable pressure drop from the inlet to the outlet of the softener at the service flow required for the application. Use a maximum service flow pressure drop guideline of 15 pounds per square inch (psi)—1 bar—for the valve alone.

Water softener flow ratein litres

Summary: Water softener design and setup can be a confusing thing to learn regardless of the application. Here are basic guidelines for engineers and technicians to study to gain a fundamental understanding of this process.

Yes, but only if you can reach the appliance with a 1/4" tube from the under sink RO unit. Pressure is a consideration with some refrigerators, so it's a good idea to check with the manufacturer. The pressure you'll get from the RO unit is about 2/3 of the incoming line pressure.

It is essential. The water pressure is what forces the water through the membrane for purification and flushes the rejected solids away. Low water pressure will result in reduced production and premature fouling of the membrane. The ideal pressure for operating an RO system is 60 PSI. Pressure below 40 PSI is generally considered insufficient, and should be boosted using a pressure booster pump.

Generally, the tank is filled to ½ to 2/3 of the total tank volume. The depth of cation resin should be at least 24” (0.6 m) in smaller tanks and 30” (0.75 m) in larger tanks. The tank should be tall enough so the resin can expand to at least 50 percent of its normal depth into the void space. Refer to the accompanying chart for standard tank sizes.

For example, assume the water has a hardness—as (CaCO3)—of 13 grains/gallon [222 milligrams per liter (mg/L), calculated by multiplying 13 grains by 17.1]—and that 20,000 gallons (75.8 m3) of water must be treated. The total hardness is 13 grains/gallon × 20,000 gallons = 260,000 grains—16.9 kilograms (kg)—of hardness per day.

How to setflow rateonwater softener

Distillers typically remove a few parts per million more of common mineral constituents like sodium. However, distillers lack efficiency when it comes volatile chemicals with a low boiling point. E.g. chloramines, which many cities now use instead of chlorine as a disinfectant, aren't as effectively removed by distillers. Reverse osmosis paired with carbon filters, however, does a very good job of removing evidence of chloramines. Unless volatile chemicals like chlorine are removed by carbon filtration before they enter the distiller, they will be released into the air or end up in the distilled water. Nonetheless, both methods produce very pure water.

Because they produce great-tasting, very pure water at a reasonable price when compared to buying bottled water, and in a trouble-free, fully automatic format to boot. Committed water drinkers know, not all water tastes the same.

The volume of cation resin required for a given flow rate can be determined two ways: 1) By the volume of resin which concerns contact time, and 2) by the resin bed (the tank) cross section area that concerns pressure drop in the resin bed. See Table 1 to determine the cross section area of the most popular size tanks.

This requirement of correct softener design may be the most overlooked factor, especially in warm water regions such as Latin America. The flow must be sufficient to expand the bed at least 50 percent. Use the following guidelines but, for exact backwash flow requirements, refer to the backwash requirements vs. water viscosity chart from your resin supplier.

The following is an introductory article offering practical advice on sizing and setting up water softeners for residential, commercial and non-critical industrial applications. There are significant variations and details not within the scope of this presentation but that deserve further investigation such as alternate methods of brining and regeneration cycle programming. Feel free to surf the WC&P “archives” at www.wcponline.com for more on these subjects. Meanwhile, read on.

Water softener flow rate0

It depends on what you mean by waste. A home RO unit uses water to clean itself and wash away impurities, much like most other water-using appliances. Considering we also use water to wash clothes, dishes, cars, and to flush toilets, a reverse osmosis unit uses more water in its operation than you actually consume, but not enough to effect your water bill. However, the RO unit only uses water while it's filling its storage tank. Once the tank is full, the unit shuts down and no water runs to drain-- think two or three extra toilet flushes a day.

Only pre filters and post filters need to be replaced on an annual basis to ensure proper performance. Ultimately, the quality of the water and the amount of use will determine the frequency of filter changes. Depending on the point-of-use RO model, the annual cost is less then $0.30 per day. The RO membrane itself will normally last between two and five years.

By contact time—Use 5 gallons per minute per cubic foot (gpm/ft3), or 42 cubic meters per hour per cubic meter (m3/h/m3), for continuous flow and 7.5 gpm/ft3 (60 m3/h/m3) for peak flow. To achieve low hardness leakage as required in applications like boiler water treatment, the flow rate should be limited to 3 gpm/ft3. By resin bed area—Use 10 gpm per square foot (ft2), or 25 m3/h per square meter (m2), for continuous flow and 15 gpm/ft2 (37 m3/hr/m2) for peak flow. To assure low hardness leakage, limit the area flow to 8 gpm/ft2.

Robert Slovak is president of Aroman Inc., a water treatment consulting company in Incline Village, Nev., and currently serves as a water consultant and manufacturer’s representative in Brazil for products imported by AquaCorp LTDA in Rio de Janeiro. He is also a member of the technical advisory committee of Agua Latinoamérica, a sister publication to WC&P, and a former member of a similar WC&P committee. He and his brother, Jack, were founders of Water Factory Systems, now a division of CUNO Inc. Slovak can be reached by email: [email protected]