17
B. Appendix C (System Specification)
B.1 Estimate flow rate and record pressure
Place a 5 gallon bucket at the water source and allow it to flow without restriction into the bucket.
Time how long it takes to fill to the 5 gallon point.
Example
Volume of Bucket
(in gallons)
5
x 60
=43 GPM
Time to fill bucket
(in seconds)
7
Backwash requirements
A 1” filter requires 30 GPM at 40 PSI to backwash properly.
A 2” filter requires 40 GPM at 40 PSI to backwash properly.
If this flow and pressure for backwash can’t be maintained while irrigating, the flow to irrigation must be stopped (using a controlled outlet valve)
while the filter backwashes.
Static (and dynamic) pressures over 100 PSI require a pressure regulator.
B.2 Rank your water source
Flow is dependent on Water Source Quality and the micron size of the screen. The following chart defines the maximum flows allowable
based on Water Source Quality and screen micron size. Most applications will follow the Average, Poor or Very Poor lines. Water source
should be rated at worst case scenario if water quality varies during the year (such as algae blooms during summer). A general guide to
Water Quality is also shown below.
Good
Average
Poor
Very Poor
Solids
< 20 ppm
< 40 ppm
< 80 ppm
< 110 ppm
Example
Well Water, municipal
supply or equal.
Clear lake water or equal
River water.
Brown or green water
(mud/algae).
Contamination
Very little, 100% clear,
similar to drinking water
quality.
95% clear water, small
contaminants. No real
discolouration of the
water.
Light to medium
discolouration.
Heavy discolouration.
Medium algae, visible silt/
dirt etc.
Maximum Flow
Filter Size
1"
2"
1"
2"
1"
2"
1"
2"
Screen
size
400
micron
(47 mesh)
40
GPM
9
m
3
/h
100
GPM
22.7
m
3
/h
40
GPM
9
m
3
/h
100
GPM
22.7
m
3
/h
36
GPM
8.2
m
3
/h
55
GPM
12.5
m
3
/h
Not
recommended
35
GPM
8
m
3
/h
200
micron
(88 mesh)
40
GPM
9
m
3
/h
100
GPM
22.7
m
3
/h
37
GPM
8.4
m
3
/h
85
GPM
19.3
m
3
/h
33
GPM
7.6
m
3
/h
50
GPM
11.4
m
3
/h
30
GPM
6.8
m
3
/h
150
micron
(100 mesh)
40
GPM
9
m
3
/h
95
GPM
21.6
m
3
/h
33
GPM
7.5
m
3
/h
70
GPM
15.9
m
3
/h
Not
recommended
40
GPM
9
m
3
/h
Not
recommended
100
micron
(150 mesh)
30
GPM
6.8
m
3
/h
75
GPM
17
m
3
/h
25
GPM
5.7
m
3
/h
45
GPM
10.2
m
3
/h
Not
recommended
