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Frequently Asked Questions - Softeners
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What are the five
cycles of a water softener? Service, Backwash, Brine,
Slow Rinse, Fast Rinse
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How is the softening
process controlled? Click on question for
answer.
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Why add salt to a water
softener? Click
on question for answer.
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Why buy a water
softener?
Click on question for answer.
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Why buy a Water King water
softener? Click on question for answer.
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How do you size a
water softener?
Click on question for answer.
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Do you have an example set of
calculations for softener sizing?
Click on question for answer.
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What is a Super Flow Kit? A super flow or service flow
by pass kit consists of and inlet and outlet diaphragm valve, some tubing
and fittings, and a solenoid. The solenoid opens the valves when the Task
Master III is in service and closes when it is in regeneration. See
Catalog Section
370.
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How can I tell which softener is in service / stand-by?
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How much water does it take to regenerate? It takes about 3 to 4 % of
the produced water to regenerate a softener. For a specific softener, the
volume of water for regeneration can be accurately calculated knowing the
cycle times and flow rates.
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What is a Shut
Off Kit? A shut off kit prevents the bypass of hard water during
regeneration. The Task Master III is ported to automatically allow water
to bypass hard water during regeneration. For simplex units this is useful
to avoid cutting off the water during regeneration. A shut off kit
consists of outlet diaphragm valve, some tubing and fittings, and a
solenoid. The solenoid closes the valves when the Taskmaster III is
in regeneration. It is open during service. See catalog section
370.
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What is N+1
Sparing?
Answer: Sizing a
system so that N units supply the required flow and capacity and a third
of the same size is added for redundancy.
Discussion: Redundancy is a basic principle of sizing of any process
equipment. The idea is to always be able to take at least one process unit
out of service and still be able to maintain production. Hence, if you
have two process units, one should be able to handle full production. If
you have three process units, two should be able to handle full
production. The expectation is to have one spare unit or N+1.
The use of N+1 sparing in water softeners.
Let us consider a required flow of 600 gpm.
Case 1, N=1: The flow could be provided by one unit at 600 gpm and then
for redundancy, an additional 600 gpm softener can be installed. In this
first case, N = 1 and N+1 = 2. The required capacity per unit is 600/1 =
600 gpm.
Case 2, N=2: In this case, the flow is provided by two units at 300 gpm
with an additional 300 gpm softener. In this case, N = 2 and N+1=3. The
capacity per unit is 600/2 = 300 gpm.
Case 3, N=3: We could use three units at 200 gpm each with one 200 gpm
spare. In this case, N = 3 and N+1=4. The capacity per unit is 600/3 =
200.
Once the peak flow requirement is determined, flow requirements for the
individual units are easily determined based on N+1 sparing.
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What are the different system
configurations available for water softeners? Water King offers
a wide variety of system and tank configurations that help to perform many
different tasks. These configurations are named according to the
number of tanks:
|
System Name |
Abbreviation |
Number of Vessels |
Number of Brine Tanks |
ERCd |
ERCt |
SECONDARY |
NUMBER OF
FLOW METERS |
|
Simplex |
SX |
1 |
1 |
|
S |
|
0 |
|
Simplex Metered |
SM |
1 |
1 |
S |
|
|
1 |
|
Twin Alternating |
TA |
2 |
1 |
S |
|
S |
1 |
|
Twin Sequential |
TS |
2 |
2 |
S |
S |
|
1 |
|
Twin Parallel |
TP |
2 |
1 |
SS |
|
|
2 |
|
Triplex Sequential |
TXS |
3 |
2 |
S |
SS |
|
1 |
|
Triplex Parallel |
TXP |
3 |
2 |
SSS |
|
|
3 |
|
Quad-Plex |
Q |
4 |
2 |
S |
|
|
1 |
|
Quad Sequential |
QS |
4 |
2 |
S |
SSS |
|
1 |
|
Quad Parallel |
QP |
4 |
2 |
SSSS |
|
|
4 |
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How do I size
a twin alternating system? Size the unit using Water
King standard sizing: Size the piping so that each of the units will
handle the full peak flow. Size the capacity so that each of the units can
handle half of the grains per day of hardness to be removed.
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How do I size
a triplex system?
Size the system using N+1 sparing: For a triplex with N+1, size the piping
so that each of the units will handle half of the peak flow. Size the
capacity so that each of the units can handle half of the grains per day
of hardness to be removed. This sizing follows N+1 sparing.
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Are there different ways to choose the capacity of a multiple tank water
system? Yes, the
sizing depends on the time between regenerations or the minimum run time
choosen by the designer.
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What is the minimum time between regenerations?
Answer: Operationally
softeners should be regenerated at 6 hour intervals. (6 to 12 hours is
used for design purposes)
Discussion: The minimum time between regenerations is first set by the
regeneration cycle, which is usually two hours. The other issue is the
recovery time of the brine tank. After brining, the brine tank must refill
and then the salt must dissolve to create a saturated brine. The minimum
time is generally set at six hours which is two hours for the regeneration
cycle and four hours for the brine tank to recover.
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How do I size the inlet and outlet headers for a softener or filter?
Answer:
For simplex systems you should match the softener inlet / oulet piping
size.
For twin alternating systems you should match the softener inlet / oulet
piping size.
For triplex at N+1 size the header to match two of the units. So if you
have a triplex with 3" piping, size the header so that the cross sectional
area is the same as two 3" pipes at 7.07 in2 each or 14.14 in2 total.
Calculating the minimum diameter gives D = Sqrt((4/PI)*14.14) = 4.24
inches. The veloicity of flow in a 4" pipe at 350 gpm is 8.9 fps so this
would not be an unreasonable choice. A 6 inch diameter pipe would assure
full flow and can supply all three units making higher flows available.
Answer: 4" is adequate, 6" provides for expansion.
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How do I convert
Conductivity to Total Dissolved Solids (TDS)?
Answer (from Stevens Water):
"Electrical Conductivity sensors are used to measure the
ability of water to carry an electrical current. Absolutely pure water is
a poor conductor of electricity. Water shows significant conductivity when
dissolved salts are present. Over most ranges, the amount of conductivity
is directly proportional to the amount of salts dissolved in the water.
The amount of mineral and salt impurities in the water is called total
dissolved solids (TDS). TDS is measured in parts per million. TDS tell how
many units of impurities there are for one million units of water. For
example, drinking water should be less than 500 ppm, water for agriculture
should be less than 1200 ppm, and high tech manufactures often require
impurity-free water. One way to measure impurities in water is to measure
the electric conductivity of water.
A conductivity sensor measures how much electricity is being conducted
through a centimeter of water. Specific conductivity is expressed as mhos
per centimeter (M/cm), sometimes called siemens per centimeter (S/cm).
Because a mho (or siemen) is a very large unit, the micromho (microsiemen)
or millimho (millisiemen) typically is used (mS/cm).
To convert the electric conductivity of a water sample (mS/cm) into the
approximate concentration of total dissolved solids (ppm), the mS/cm is
multiplied by a conversion factor. The conversion factor depends on the
chemical composition of the TDS and can very between 0.54 – 0.96. A value
of 0.67 is commonly used as an approximation if the actual factor is not
known [(TDS)ppm = Conductivity µS/cm x 0.67].
Since conductivity varies with temperature, it is necessary to correct
the readings for changes in temperature. Most instruments contain circuits
that automatically compensate for temperature and correct the readings to
a standard 25°C.
Water purity varies widely. Therefore, Greenspan offers conductivity
ranges from 0 – 70,000 µS/cm."
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