RP-01638

At a standard frequency of about 40 strokes
per minute, the same 20-L can was filled to
capacity while counting the actual number
(n,) of strokes. The volumetric efficiency was
then computed from the formula:
Volumetric efficiency (%) _ (nu,/n,) x 100
The water head (distance between the
water level in the well and the pump spout)
was measured by using a calibrated string
weighted at one end with a float.
Since no counter was installed to measure
pump usage, the determination of total
volume of water pumped was estimated.
Monitors at the village recorded the number
of 20-L cans (provided at the pump site for
this purpose) that the village people pumped
per day. This was used as the basis to estimate
the amount of water pumped per month.
The thickness of the upper and lower
piston rings at three points was measured
monthly. The percentage rate of wear was
then determined from the past and present
measurements.
Highlights of Findings
The project was able to install 30 Waterloo
pumps in several areas: Jala Jala Islands in
Laguna (10), Cavite (9), Pangasinan (7), and
Nueva Ecija (4). Of these 30 pumps, only 4
(13%) were considered functional/operational
and appropriate for monitoring purposes.
The other 26 pumps were eventually abandoned
as they were beset with one or more
of the following seven problems: (1) high
leakage rate; (2) users found the pump to be
very difficult, strenuous, and inconvenient to
use because it took quite a long time to prime
and draw water. (This situation is described
with humour by one user with the following
statement: "Our sweat comes out first before
we pump out water."); (3) defective foot
valve; (4) caving in of the well; (5) people
eventually abandoning the use of the pumps
because they started to draw up brackish or
muddy water; (6) piston stuck and could not
be extracted; and (7) foot valve slipped out of
the casing and dropped down the well.
Given the alternative of being able to use
other existing pumps (Jet-matic and pitcher
pumps), the village users eventually switched
to these other pumps. The original Waterloodesigned
handpump that was fabricated
according to specifications did not function
as efficiently as expected when tested
initially. The following specific observations
were made.
The foot valve did not hold water satisfactorily
because: (1) the original gasket or the
seal (polyethylene ring) was not effective;
(2) sand particles became trapped between
the plastic flapper valve and the valve seat
and caused poor seating of the valve; and
(3) there was excessive clearance between the
valve guide and the flapper valve. The piston's
performance was similar to that of the foot
valve.
Filter
The PVC filter did not function adequately.
This may have been because the screen slots
were too big and allowed fine sand and silt to
pass. Another reason was that some wells
were not adequately developed.
To try to overcome these problems,
changes were made in the design of the foot
valve. These changes included incorporating a
brass spring, using a rubber gasket, and
chamfering the valve seat to prevent sand
particles from wedging between the flapper
valve and the valve seat. These modifications
improved the performance of the pumps
slightly. However, it is not possible to state
conclusively whether the improved performance
was due solely to the modifications or
was due to the fact that the wells had louver
pumping heads: the four operational pumps
had a water head of less than 10 feet (3 m).
Even when the Malaysian foot-valve design
was tried, technical problems with the foot
valves continued to be a major constraint.
One interesting finding that has always
puzzled the team is the seepage rate encountered
in all the wells. Although a stronger
spring was installed for the flapper valve, a
high seepage rate persisted. This meant that
50-70 strokes of the pump handle were
required to raise the water column so that
water could be obtained; however, after a
short period without pumping, the level of
the water in the column fell back to the level
of the ground water. Thus, priming had to be
repeated. For areas with a high water table,
like Aliaga, Nueva Ecija, and Pangasinan,
the tedious process of raising the water
column was not much of a problem. For
deep wells, however, this is a very serious
problem.
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