2020 Web Catalog - Flipbook - Page 486
17 Water System Selection
WATER SYSTEM SELECTION:
In selecting the proper water system for a given installation,
facts about the water source as well as the water
requirements must be considered. Assuming the water
source is a well, the following information is needed:
1. Well size – (diameter)
2. Depth to pumping level
3.Well capacity (maximum pumping rate it will sustain)
4. Elevation and total length of piping
5. Amount of capacity required
6. Amount of pressure required
The inside diameter of the well must be known since it may
be the determining factor as to the type of pump which can
be used. Submersible pumps require well at least 4 inches
in diameter. Packer type jet systems can be installed in
wells with diameters as small as two inches.
The depth to the water level at maximum draw down
determines the type of pump that must be used. For depths
of 25 feet or less, at or near sea level, shallow well “suction
lift” type pumps are adequate. Each 1000 feet of elevation
above sea level reduces the shallow well depth limit by one
foot. For example, the maximum practical suction lift in the
Denver area, which is 5000 feet above sea level, would be
25 minus 5, or 20 feet. For lifts greater that the maximum
suction limit, deep well type pumps, which have a pumping
mechanism in the well, are required. The pumping level may
be estimated from the well drillers test log.
The maximum pumping rate the well will sustain must be
known to assure that the capacity of the water system
selected does not exceed that rate. As in the case of
pumping level, well capacity may be obtained from the well
Technical & Engineering
ELEVATION AND TOTAL LENGTH OF PIPING:
The elevation the total length of piping are required to
compute the pressure drop in the system. This computation
is made by adding the elevation to the drop caused by pipe
friction. Pressure drop due to friction is calculated by using
the friction loss tables.
AMOUNT OF CAPACITY REQUIRED:
In determining the required capacity of a water system, it
is important to provide for the peak demand rather than for
the average use rate. A good rule of thumb to follow is to
allow for one gallon per minute of pump capacity for each
household outlet. For farm water systems, adequate water
must not only be provided for household purposes and
animal drinking, but for cleaning and fire protection as well.
Average water consumption per day for various animals is
shown in Table 1. The pump selected should have sufficient
capacity to pump the entire daily requirement in two hours.
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As an example, assume a farm with 20 milk cows, 100
hogs, 500 chickens, two milk houses and eight household
outlets. The daily water consumption of the animals would
be as follows:
Milk cows —
20 x 35
100 x 4 = 400
500/100 x 6 = 30
Total Daily Usage 1130
Pumping Capacity for 2 Hours (120 minutes)
1130 ÷ 120 = 9.4 G.P.M.
Milk House Outlets = 2.0
Household Outlets = 8.0
A 19 gallon per minute pump will provide sufficient water for
the farm needs, including fire protection. The Well Capacity
should be compared to the Pump Capacity to make sure the
well can sustain a pumping rate of 19 gallons per minute.
If it will not, an extra large pressure tank, or a two-pump
system with storage tank will be required.
AVE. WATER CONSUMPTION FOR HOME/FARM USE
A. Home Use
For overall daily consumption, checks of families of
various sizes in different parts of the country indicate 100
gallons per day per person is a very good average.
Toilet - Flush
Washer - Automatic
up to 150
Garden Hose 1/2"
Garden Hose 3/4"
Sprinkler - Lawn
B. Farm Use
Gallons Per Day
Horse, Mule, Steer
(Based upon a study of over 20 sources by the Water Source and Use Subcommittee of
the Water Systems Council. Values given are average. They do not include the extremes.)
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