Softener Equipment

Sodium zeolite softener systems consist of a softener tank, valving and a means of transporting brine (salt solution) to the softener tank.  The tank includes a service and rinse water inlet distributor, freeboard or the headspace from the top of the resin bed to the top of the vertical wall of the tank, a regenerant distributor, a bed of ion exchange resin and sometimes a supporting medium or outlet distribution system.

The inlet assembly is designed to evenly distribute the incoming water.  It also acts as a collector for the backwash water that goes to the sewer.

The feedboard space allows the resin to expand without loss to drain during the backwashing.  It should be designed to permit a minimum of 50% expansion.

The regenerant distributor located above the resin bed, spreads the brine uniformly over the resin beads.

A bed of resin, operating in the sodium cycle, softens the water.  The quantity of resin used depends on the raw water hardness, the quantity of water to be treated per regeneration, flowrate, and the regenerant level employed.

An underdrain system evenly collects the treated water, waste brine and rinse water, and distributes the backwash water.

It is not unusual to have a valving system that consists of either a valve nest or a single, multiport control valve.  A nest of six (6) main valves is needed for the service inlet and outlet, backwash inlet and outlet, brine inlet and rinse outlet.  The valves may be either manually operated or any variety of air-, water- or motor-operated automatic valves.  A single, multiport control valve may be used in place of the valve nest.  As the multiport valve moves through a series of four positions, the ports in the valve direct the flow of water in the same manner as the opening and closing of separate valves.

The brining system consists of a salt dissolving/brine – measuring tank.  It is used to prepare a saturated brine solution.  This tank frequently has a float – operated valve to control the fill and drawdown level and thus, the quantity of brine added to the softener.  Usually an eductor transfers the saturated brine to the softener and dilutes the saturated brine with inlet water to the desired concentration for resin regeneration.

A future article will include a guide to softener troubleshooting along with additional information on softener operation and maintenance.

Health Department Finds Cause of Legionnaires Outbreak

“NORTH PORT, FL (WWSB) – According to a report completed by the Florida Department of Health, the growth of legionella bacteria was found in a hot water heater at the fitness area of IslandWalk.

Testing was also done on the community swimming pool and spa, but returned negative results.

 Despite the negative finding the health department says it believes the pool and spa area are where people came in contact with the bacteria.

13 people tested positive for the disease in late February.

 IslandWalk at the West Villages

Copyright 2018 WWSB. All rights Reserved.”


Softener Operation and Regeneration

Softener Operation

A sodium zeolite softener operates through two basis cycles:  the service cycle, which produces soft water, and the regeneration cycle, which restores the exhausted resin to capacity.  During the service cycle, raw water enters the softener through the inlet distributor, flows through the resin bed, is collected by the underdrain system and then transferred to the point of use.

When a softener is exhausted, it must be regenerated.  A number of methods may be used to signal the need for regeneration.  Many facilities rely on operator testing to determine when hardness breaks through.  Another common method for determining when regeneration is needed is to measure the quantity of water treated between regenerations.  A water meter in the service water line is used to sound an alarm or automatically initiate regeneration when a preset number of gallons has been softened.

Softener Regeneration

As we have said, regeneration is the process by which the resin is exposed to a strong concentration of highly ionizable material, such as salt.  While the resin has a greater affinity for calcium and magnesium than for sodium, the high concentration of the regenerant forces the ions on the bead into solution and substitutes the sodium ion.  This process is called elution.  The concentration of the regenerant is a critical factor in all ion exchange.  Softener regeneration generally consists of four (4) steps:

  1. Backwash
  2. Brining
  3. Slow Rinse
  4. Fast Rinse


Backwashing is an upward flow of water which lifts and expands the resin bed.  It removes the accumulation of particulates (entering via raw water) and resin fines (broken pieces of resin).


The brine regenerant stream enters the softener, flows downward through the resin bed and then is discharged to waste.

Slow Rinse:

A low flow rate of rinse water follows the regenerant to displace the brine downward through the resin bed while slowly rinsing the unit.  The flow rate for this slow rinse step is the same as the flow rate for the brining step.

 Fast Rinse:

A high flow of rinse water follows the slow rinse procedure to remove residual brine from the resin bed.  The flow rate for the fast rinse step is identical to the flow rate while the softener is in the service cycle.

Usually a unit can return to service as soon as the hardness value reaches the desired preset level, but some operators continue to rinse until chlorides are reduced to a value near that of the influent level.

Again, the frequency at which any resin must be regenerated is a function of:

  1. The volume of water treated.
  2. The concentration of exchangeable ions in the water.
  3. The type of resin.
  4. The amount of resin present.
  5. The type of regenerant.
  6. The amount of regenerant.


Principles of Zeolite Softening

Principles of Zeolite Softening

Sodium zeolite softeners use exchange resins made of polystyrene.  These resins have sodium ions loosely attached and will readily give up sodium for more desirable ions such as calcium and magnesium.  This exchange is only for cations (positively charged ions).  This is why sodium zeolite resin is referred to as a cation exchange resin (Figure 2).


Figure 2 – Sodium zeolite resin gives up sodium ions for calcium and magnesium

The water to be softened passes through the vessel containing resin.  Calcium and magnesium ions are exchanged for the sodium ions in and on the resin beads.  The sodium then takes the place of the calcium and magnesium with the appropriate anion (negative component).

A plot of the softener effluent profile shows a low, nearly constant effluent hardness level until the ion exchange resin nears exhaustion.  At this point, the hardness level usually increases quite rapidly and regeneration is required (Figure 3).

Figure 3 – As the resin nears exhaustion, the hardness level increases rapidly.

Regeneration is achieved by reversing the softening reactions.  Exhausted resin is exposed to a concentrated solution of sodium chloride.

Normally, zeolite resin more readily releases sodium in exchange for calcium and magnesium.  However, with the high concentration of sodium in the brine, the sodium ions displace the calcium and magnesium ions attached to the beads.  Thus, the high concentration of salt in the regenerant supplies the driving force to replace the hardness cations.  The calcium and magnesium are removed from the softening unit through the wave brine and rinse streams.

The frequency of regeneration needed depends on the rate or quantity of water, the calcium and magnesium content of the raw water, the quantity of exchange resin in the softener and the amount of salt used per regeneration.  The operating plant usually controls only the flow and the amount of regenerant.  The other parameters are fixed by the system design and the raw water hardness level

Softener Application and Ion Exchange

Softener Application

The potential for scale and deposit buildup exists in every raw water supply.  The ability of the sodium zeolite softener to reduce this potential effectively and economically makes this an ideal pretreatment for boiler feedwater and many types of chemical process waters.  Compared to other softening methods, sodium zeolite units offer many advantages:

  1. The treated water has a very low scaling tendency because this method reduces the hardness level of most water supplies to less than one part per million (ppm).
  2. Operation is simple and reliable; automatic regeneration controls are available at a reasonable cost.
  3. Regeneration is accomplished with inexpensive, easy-to-handle salt (NaCl).
  4. Waste disposal usually presents no problem.
  5. Within limits, variations in the water flow rate have little effect on the treated water quality.
  6. Efficient operation can be obtained in almost any size unit, making sodium zeolite softeners suitable for both large and small installations.

The Ion Exchange Process

Ion exchange is the process in which materials exchange one ion for another, hold it temporarily, and release it to a regenerating solution.  These materials are widely used to treat raw water supplies which contain dissolved salts.  Today the most commonly used material is an ion exchange resin.  Resins are plastic beads to which a specific ion has been attached – an ion which is exchanged for other ions in the water supply (Figure 1).  Once the resin has given up or exchanged most of its exchangeable ions, it is said to be exhausted and needs to be regenerated by coming in contact with a strong solution of ions called the regenerate.  The regeneration procedure will be explained in detail later in this article.

Cold Crystallization

One of the key objectives of effective cooling water management is to prevent the precipitation of scale-forming minerals onto heat transfer surfaces.  Scaling potential is highest at the hottest metal surfaces, and where the transfer of heat occurs from a process into the cooling water “ across plate/frame or shell and tube exchangers.  However, it is also possible for scaling to occur at the other end of the process where heat is removed.  Since cooling towers evaporate water to reject that heat, mineral deposition also happens within the tower itself.  Some have dubbed this phenomenon Cold Crystallization, and owners will experience operational problems related to the condition.  Reduced flow, congestion, accumulation of suspended matter, algae and biofilm can all happen within the scale matrix.

While mineral saturation is necessary for cold crystallization to manifest, another primary (but less obvious) reason is the intermittent flow of tower water.  When flow is interrupted, and airflow continues, the cycled-up cooling water is evaporated away within the tower leaving the mineral salts behind to be air-dried onto tower surfaces causing unchecked deposition.  In hard water areas, this can become a real nuisance.  How can this challenge be avoided?  By making one small but significant change in the sequence of events for an intermittent operation (or off-peak load).  Rather than cycling water flow and running fans continuously, buildings should do the opposite.  Run the cooling water pumps continuously, and cycle the tower fans “ until heat is fully dissipated and flow can safely be turned off.  Too often a BMS or EMS (Building or Energy Management System) is programmed to stop pumps and operate fans “ and it is this sequencing that causes the problem.  Keep the water flowing to eliminate cooling tower deposits.

Written by: John D. Caloritis, CWT, Technology Director The Metro Group, Inc.

What are Auditors asking for when looking at Water Management Plans to reduce the risk of Legionella?

Since the CMS’s publication of the memo requiring Healthcare facilities to adopt a Water Management Plan and to conduct regular Legionella testing to reduce the risk of Legionella in building water systems in June of 2017, the most common question we get from our clients is “What will the Auditors be asking for?”  Well, we now have firsthand experience on the subject.  In the Real Estate business, the saying is Location, Location, Location.  For Water Management, we’d have to say it’s Documentation, Documentation, Documentation. 

 In each instance where our clients have had visits from certifying agencies and government regulators, the first question on Water Management is “Can I see your Plan?”  The physical documentation of your facilities Water Management Plan for the reduction of the risk associated with Legionella in building water systems is paramount for staying in compliance.  Your Plan Document binder should include the most recent test results, maintenance logs, really anything related to implementation of the control measures and corrective actions laid forth in the plan document.  The more documentation the better.

 If Metro can be of assistance with your facilities Water Management Plan, please get in touch today:



Keep the Water Flowing

Keep the Water Flowing.  This statement represents one of those basic rules of thumb in managing any water system.  Lack of flow can lead to wide-spread system problems with microbial fouling, corrosion and even fouling from sediment.  Without flow and turbulence, water systems will accumulate dissolved gases, suspended sediment will separate from bulk waters, and at the right temperatures biological/organic fouling will be initiated.  Chemical inhibitors cannot do the appropriate job of passivating metal unless present in the water stream at appropriate concentrations and are flowing past those surfaces.  Organisms will flourish in stagnant zones and, depending upon the length of downtime, bacteria will form masses of sessile communities ultimately leading to MIC (microbiologically influenced corrosion).  It is human nature to pay closer attention to operating equipment and to lose track of off-line equipment.  Systems that must be left idle for extended periods of time should receive special planning and additional PM.  Steps to Take? Start system pumps for 1 – 2 hours a minimum of once weekly, test for and adjust chemical treatment levels, and clean/change any filter media or strainers.  This is all simple to do, but often overlooked.

Written by: John D. Caloritis, CWT, Technology Director The Metro Group, Inc.

Modern HVAC Design

Modern HVAC design often employs a wide selection of metals which are used in system components and transmission lines.  New construction specifications require protection for systems comprised of steel, copper, bronze, stainless steel, galvanized and even aluminum.  In most cases, multiple metals are usually present in any given system.  In addition, some component suppliers specify/demand unique water chemistry conditions for their component, while they may or may not be compatible with protection strategies for other parts of the system.  Talk about a delicate balancing act! These facts require that careful consideration be given to corrosion control and to metal preparation/passivation.  Corrosion monitoring beyond warranty periods ensures consistent protection, smooth operations, and extended equipment life.  Facility Managers and Plant Engineers are encouraged to lean heavily on the water treatment industry for guidance and support.  The Metro team is in your corner.  Our product line is flexible and capable of handling this balance.   Cleaning/passivation strategies are also designed with these variables in mind.

Written by:

John D. Caloritis, CWT, Technology Director The Metro Group, Inc.

Glycol Systems

Glycol systems present Facility Managers with a host of new challenges and opportunities.  Protecting systems from freezing in cold weather climates is critical.  However, glycol can behave very differently and requires that water system conditions be carefully prepared in advance.  Without attention to detail, these systems can produce unwanted headaches.  Dealing with fouled glycol systems for example, can be very problematic. Depending upon the severity and type of problem encountered, strategies could include filtration, microbiological control, disinfection, system-wide cleaning/flushing, or even a glycol addition to correct the concentration of a fluid. Note the calculations associated with the latter are supported by using the formula:

 Δ Glycol = [Volume x (Desired % – Current %)]

(100 – Current %)

 The volume must first be nailed accurately.  With that information, the above formula will produce the amount of system volume (at the old concentration) which needs to be displaced.  Your Metro representative can be very helpful to you in working through any of these challenges.

Written by:
John D. Caloritis, CWT
Technology Director
The Metro Group, Inc.
John is Chair of the AWT (Association of Water Technologies) Cooling Water Committee and a Member of the Association’s Legionella Task Force.