Flexcon


Online Tank Sizing


To properly size your Flexcon well tank you will need to obtain the following information:

  • *The pump delivery rate in gallons/liters per minute (GPM/LPM)
  • *The recommended minimum running time of the pump
  • *The minimum (cut-in) and maximum (cut-out) system pressure parameters

Once these factors are known, the following calculations will determine, in most cases, the correct model to meet your specifications.*


Calculating Drawdown

1. Pump delivery rate in GPM/LPM
 GPM/LPM
2. Desired minimum pump running time in minutes
(1 minute, 45 seconds = 1.75 minutes)
 Minutes
3. Multiply line #1 by line #2. This is the minimum drawdown or available water volume required in Gallons/Liters. *
 Gallons/Liters   

Calculating Tank Size

4. Minimum system pressure (cut-in)
 PSIG/kPa/bar
5. Maximum system pressure (cut-out)
 PSIG/kPa/bar
6. Using the Drawdown Table below, find the drawdown factor applicable to lines #4 and #5.
 Factor
7. Divide line #3 by line #6 to determine the minimum total volume required.
 Gallons/Liters 

The figure that is calculated on line #7 is the total tank volume required based on the given design criteria. (see example below)  With this information in hand you can refer to the Flexcon sizing charts below to select the proper tank for your application. You will want to choose a tank with the lowest volume capacity that is greater than or equal to the total required volume.

* If a volume of water needed is greater than the amount calculated on line #3, enter that amount on line #3 in place of the calculated volume

Example:

An application using an 8 GPM pump with a minimum run time of 1 minute and a 30-50 PSIG system pressure range;

8 GPM x 1 minute

26.7 gallon minimum tank capacity.

=

.30 (factor)


In the example above our total required volume for this application is 26.7 gallons. Using the Challenger Series Sizing Chart as an example we find that the 125-PC88 model has a total volume of 26.0 gallons, slightly less than our requirement. In this case you would want to move up to the 130-PC111 model with a total volume of 32.0 gallons, the smallest tank available with a capacity greater than or equal to our minimum requirement.

Tank Sizing Charts

Please visit our Tech/Literature page for additional model sizing information...

Table #2 - Drawdown Factors

 System Pressure
(cut-out) PSIG / (kPa) / bar

Mimimum System Pressure (cut-in) -- PSIG / (kPa) / bar

20
(138)
1.38

25
(173)
1.72

30
(207)
2.06

35
(242)
2.41

40
(276)
2.76

45
(311)
3.10

50
(345)
3.45

55
(380)
3.80

60
(414)
4.16

65
(449)
4.48

70
(483)
4.83

75
(518)
5.17

80
(552)
5.51

85
(587)
5.86

90
(621)
6.20

95
(656)
6.55

100
(690)
6.89

105
(725)
7.24

110
(759)
7.58

30 / (207) / 2.06

0.21

35 / (242) / 2.41

0.28

0.19

40 / (276) / 2.76

0.34

0.26

0.17

45 / (311) / 3.10

0.39

0.32

0.24

0.16

50 / (345) / 3.45

0.44

0.37

0.30

0.22

0.15

55 / (380) / 3.80

0.47

0.41

0.34

0.28

0.21

0.14

60 / (414) / 4.16

0.50

0.44

0.38

0.32

0.26

0.19

0.13

65 / (449) / 4.48

0.53

0.48

0.42

0.36

0.30

0.24

0.18

0.12

70 / (483) / 4.83

0.56

0.50

0.45

0.40

0.34

0.29

0.23

0.17

0.11

75 / (518) / 5.17

0.53

0.48

0.43

0.38

0.32

0.27

0.22

0.16

0.11

80 / (552) / 5.51

0.50

0.46

0.41

0.36

0.31

0.26

0.21

0.15

0.10

85 / (587) / 5.86

0.48

0.43

0.39

0.34

0.29

0.24

0.20

0.15

0.10

90 / (621) / 6.20

0.46

0.42

0.37

0.32

0.28

0.23

0.19

0.14

0.09

95 / (656) / 6.55

0.44

0.40

0.35

0.31

0.27

0.22

0.18

0.13

0.09

100 / (690) / 6.89

0.42

0.38

0.34

0.30

0.26

0.21

0.17

0.13

0.09

105 / (725) / 7.24

0.41

0.37

0.33

0.29

0.25

0.20

0.16

0.13

0.08

110 / (759) / 7.58

0.39

0.35

0.31

0.27

0.24

0.20

0.16

0.12

0.08

115 / (794) / 7.92

0.38

0.34

0.30

0.26

0.23

0.19

0.15

0.11

0.08

120 / (828) / 8.27

0.36

0.33

0.29

0.25

0.22

0.18

0.15

0.11

0.07

125 / (863) / 8.62

0.35

0.32

0.28

0.25

0.21

0.18

0.14

0.11


In keeping with current industry standards, drawdown factors are based on Boyle’s Law. Actual drawdowns will vary depending upon system variables including the accuracy and operation of the pressure switch and gauge, actual precharge pressure, and operating temperature of the system.