02 Water Collection:
Description
This article is from the Water Treatment FAQ, by Patton Turner with numerous contributions by others.
02 Water Collection:
Wells: Water can only be moved by suction for an equivalent head of
about 20' After this cavitation occurs, that is the water boils off
in tiny bubbles in the vacuum created by the pump rather than being
lifted by the pump. At best no water is pumped, at worst the pump is
destroyed. Well pumps in wells deeper than this work on one of three
principles:
1) The pump can be submerged in the well, this is usually the case for
deep well pumps. Submersible pumps are available for depths up 1000
feet.
2) The pump can be located at the surface of the well, and two pipes
go down the well: one carrying water down, and one returning it. A
jet fixture called an ejector on the bottom of the two hoses causes
well water to be lifted up the well with the returning pumped water.
These pumps must have an efficient foot valve as there is no way for
them to self prime. These are commonly used in shallow wells, bust
can go as deep as 350 feet . Some pumps for use the annular space
between one pipe and the well casing as the second pipe this requires
a packer (seal) at the ejector and at the top of the casing.
3) The pump cylinder can be located in the well, and the power source
located above the well. This is the method used by windmills and most
hand pumps. A few hand pumps pump the water from very shallow wells
using an aboveground pump and suction line. A variety of primitive,
but ingenious, pump designs also exist. One uses a chain with buckets
to lift the water up. Another design uses a continuous loop rope
dropping in the well and returning up a
small diameter pipe Sealing washers are located along the rope, such
that water is pulled up the pipe with the rope. An ancient Chinese
design used knots, but modern designs designed for village level
maintenance in Africa use rubber washers made from
tires, and will work to a much greater depth.
Obviously a bucket can be lowered down the well if the well is big
enough, but this won't work with a modern drilled well. A better idea
for a drilled well is to use a 2' length or so of galvanized pipe with
end caps of a diameter that will fit in the well casing. The upper
cap is drilled for a screw eye, and a small hole for ventilation. The
lower end is drilled with a hole about half the diameter of the pipe,
and on the inside a piece of rigid plastic or rubber is used as a
flapper valve. This will allow water to enter the pipe, but not exit
it. The whole assembly is lowered in the well casing , the weight of
the pipe will cause it to fill with water, and it can then be lifted
to the surface. The
top pipe cap is there mostly to prevent the pipe from catching as it
is lifted.
Springs: Springs or artesian wells are ideal sources of water. Like
a conventional well, the water should be tested for pathogens, VOCs
(Volatile Organic Compounds such as fuel oil or benzene), pesticides
and any other contaminants found in your area. If the source is a
spring it is very important to seal it in a spring box to prevent the
water from becoming contaminated as it reaches the surface. It is
also important to divert surface runoff around the spring box. As
with a well, you will want to periodically treat the spring box with
chlorine, particularly if the spring is slow moving. The spring my
also be used for keeping food cool if a spring house is build. If
this is the case, it is still recommended to build a spring box inside
the house to obtain potable water.
Surface water. Most US residents served by municipal water systems
supplied with surface water, and many residents of underdeveloped
countries rely on surface water. While surface water will almost
always need to be treated, a lot of the risk can be
reduced by properly collecting the water. Ideal sources of water are
fast flowing creeks and rivers which don't have large sources of
pollution in their watershed. With the small amounts of water need
by a family or small group, the most practical way to
collect the water is though a infiltration gallery or well. Either
method reduces the turbidity of the collected water making it easy for
later treatment.
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