Post on 20-Mar-2021
The Zimbabwe Bucket Pump An update
Peter Morgan
A publication by Aquamor-Zimbabwe.
February 2014
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Introduction
The “Bucket Pump” is a water lifting device which uses a tubular bucket to
raise water from a tubular well – known as a tube well. These wells are
usually drilled with a hand auger. They work best in shallow aquifers,
where the soil is soft and easy to penetrate. Where conditions are suitable a
well can be hand drilled in a few hours, then cased with a PVC pipe, which
is surrounded by a gravel pack. The pipe ascends through a concrete head-
works consisting of an apron and water run-off. The pipe is closed off at the
top with a lid. The tubular buckets are fitted with a non-return valve at the
base.
Work on this concept was carried out in Zimbabwe at the Blair Research
Laboratory in the early 1980’s. At first the tube-buckets were raised on a
rope directly by hand. Later models used a windlass system to raise the
bucket. Initially these windlass adapted bucket pumps were hand made
using treated gum poles as windlass supports. Later the concept was
commercialised, and the pumps were mass produced.
Bacteriological studies revealed that the quality of water drawn from tube-
wells fitted with tubular buckets was a significant improvement on water
drawn from wider diameter wells. This was due to the high rate of change
of water within the tubular well chamber compared to wider diameter
wells. The water in the well chamber was flushed out and rapidly replaced
by fresh ground water as water was withdrawn with the bucket.
The work on this concept was also performed using a hand operated
drilling rig, made with an auger fitted to water pipes, which were turned
with wrench spanners or cross bar. This method worked satisfactorily down
to shallow depths of up to about 6m. Later V&W Engineering designed the
VonderRig, a more sophisticated hand drilling machine. V&W also made
the commercial version of the bucket pump.
Over the years the Bucket Pump was phased out of the national program,
being replaced by the more versatile Upgraded Family Well, which used
standard buckets to raise water with a windlass system from wider
diameter, brick lined wells. Tens of thousands of these units were built and
the concept was endorsed by the Government of Zimbabwe.
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Some background
How it works
The bucket pump consists of a tubular bucket fitted with a non-return
valve at the base and a simple handle at the head. This bucket, supported
by a rope or chain is lowered and raised through a tube-well. Tube-wells
are normally hand drilled holes which enter the water table and are lined
with PVC casing. Gravel packs are introduced at the base of the casing
and around the casing. Normally these pumps are fitted to shallow tube-
wells normally less than 12m deep. They are best used at family level
where they can be looked after and maintained properly. The methods
used should be low cost, durable and easy to manage.
As the bucket descends through the water within the tube-well, it picks up
water, which passes through the non-return valve. When the bucket is
raised the valve closes, bring up a full bucket of water. This water is
poured into a bucket sitting on the well apron. The bucket can be raised
and lowered by hand direct or through a windlass system.
An important part of the Bucket Pump, as it is with an Improved Family
Well, is that a strong concrete “Apron” and water run-off are built
around the tube-well opening. These provide a hygienic environment
surrounding the well head.
Early Bucket Pump with wooden windlass supports and
surrounded by a protective apron.
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In this system there is a rapid passage of water from the aquifer into the
tube-well casing and then up within the bucket itself to the surface. This
has the effect of flushing water through the system rapidly. The overall
effect is that water quality is higher compared to larger diameter wells.
The “flushing effect” of water passing through the Bucket Pump system
The high rate of change of water in the casing, where fresh water is
constantly entering the base of the casing and being withdrawn from the
top, has a significant effect on the final purity of the water (provided that
the tube-well is properly sited). Buckets are handled at the surface, and
might be expected to take down contaminants into the tube well. However
if these contaminants enter they are rapidly diluted as water is flushed
through the system - fresh water entering the base of the tube-well to
replace water being extracted at the surface. The following table
compares E. coli levels in poorly protected traditional wells, bucket
pumps and hand pumps fitted to tube-wells. Levels of E. coli are not so
different for Bucket Pumps and Hand Pumps (in this case Blair Pumps).
Data taken from Rural Water Supplies and Sanitation. Peter Morgan.
1990. MACMILLAN
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Demonstration of the flushing effect
Supporting evidence for the “flushing effect” is shown in the following
figure which illustrates the results of an experiment where contaminants
were added to a tube-well fitted with a Bucket Pump. In the experiment a
sample was taken before the contamination was added and analysed for
bacteria (Faecal E. coli/100ml sample). The initial sample showed zero
bacteria, but reached a peak in the second bucket withdrawn after
contamination was added of 180,000 E. coli/100ml sample. This was
dramatically reduced in the following samples taken from buckets,
showing how fresh water coming from beneath diluted the concentrations
of bacteria drawn up in the buckets.
Bucket Pumps are best used in family settings where they can be well
looked after. In the family setting, the concept of ownership is resolved,
and the family itself takes on the responsibility for maintenance and
upkeep of the facility. If there is any doubt about security, the lid
covering the tube- well can be locked in place and the bucket and rope
can be taken indoors at night. It is common practice in some areas, that
the windlass is kept inside the house at night. Acknowledgments for the early work Many thanks to the Blair Team of years ago, Ephraim Chimbundi,
Fambi Gono, Philimon Ndororo, Joshua Mazanza, Felix Chawira, and
Michael Jere. Also for the support of the Ministry of Health. Jan.2014
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Basic stages of construction
This uses the following sequence:
1. Making the bucket
2. Drilling the tube well
3. Building the head-works
4. Putting to use
5. Upgrading
In this case a 165mm diameter hole is drilled into the ground
manually so that it passes the water table as far as possible. This
tube-well is fitted with a 110mm PVC casing surrounded by a gravel
pack (10mm granite chips). The bucket is hand-made using a length
of 90mm PVC piping with a handle at one and end a non-return
valve at the other end. A suitable head-works (apron and water run-
off) is built around the PVC pipe. At first the bucket can be raised
and lowered directly by hand. Several upgrades are possible, the first
being the fitting of a windlass system to keep the rope in a hygienic
position and the assist with raising the bucket. The tube well can also
be fitted with a Blair Pump or a Bush Pump if necessary if the well
provides enough water.
It is important to drill the hole as deep as possible into the aquifer.
The best drilling time is at the end of the dry season when the water
table is at its lowest. However with hand drilling the tube-well can be
drilled at any time of the year.
The simplest and cheapest version of this system does not use a
windlass. But this can be upgraded to use a windlass system. The cap
placed over the end of the PVC pipe can be locked in place with a
chain and padlock to increase security.
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Making the bucket This is made with a 500 - 800mm length of 90mm class 6 or class 10
PVC pipe with a non- return valve fitted into the base and a simple
handle fitted into the top. Start by fitting the brass non return valve.
Brass non return valves are cheap and commonly available in hardware
stores. The half or ¾ inch or one inch non return valves can be used. The
valve is inserted in a concrete plug as follows.
A length of the 90mm PVC pipe is cut off to make a mould in which the high
strength concrete is poured. This has the same length as the non-return valve.
If a metre of pipe is used, a part of this can be used to make the mould.
A mix of 2 parts clean sharp river sand (200mls) and one part PC15 ( 100mls
Portland cement) is used.
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This is mixed into a paste
And added between the valve and the PVC pipe mould
This is allowed to cure for 2 days. Then the PVC is cut, allowing the
plug of concrete which holds the valve to be released.
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The valve plug is then allowed to dry and the outer surface is then
applied with a hard setting epoxy adhesive. The lower end of the 600 -
800mm long PVC pipe is then gently heated over a flame.
The plug is then pushed into the pipe.
Fitting a handle
The cut length of 90mm pipe used to caste the concrete plug is than cut
again so it will fit inside the PVC tubular bucket. This doubles the
thickness of the bucket at this point. This is bonded with PVC cement
or fast setting adhesive.
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Holes are drilled through the double thickness of PVC pipe to
hold the wire handle. A hot nail can also be used.
A suitable length of 3-4mm wire is cut and bent into shape and
fitted in the two holes and acts as a handle
The bucket/bailer is now complete. It is good to make a second
unit as a back-up.
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Time of filling of the bucket The filling time of the bucket, once it enters the water depends on the
size of the valve and the length of the bucket. Also the open space
allowed for water passage through the valve. Some flap valves on
brass non return valves open wider than others. Also there are other
types of non-return valves that might be considered, such as a golf
ball sitting on a standard PVC fitting. The following valves were
tried and timed to fill a 500mm length bucket (carrying about
2.5litres of water).
Type of valve time to fill 500mm bucket
Half inch (12.5mm), brass 8.6 secs
¾ inch (20mm), brass 9.0 secs
One inch (25mm) brass 3.5 secs
Golf ball type 3.0 secs
Note that the ¾ inch brass non return valve allowed water to pass through
at about the same rate as the half inch valve because the flap on this ¾ inch
unit did not open fully. Clearly the most suitable brass valve is the one
inch, and if used golf balls are available – the golf ball. The golf ball type is
slightly leaky, but may last longer.
Making the “golf ball valve”
A piece of 90mm PVC casing is cut to the same height as the PVC fitting. The
fitting is placed centrally within the casing and filled with a very strong mix of
river sand and Portland cement (2:1 or even 1:1). The movement of the ball is
restricted by two galvanised steel wires 3 or 4mm thick.
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The golf ball is fitted in place followed by the two shaped galvanised steel
rods. 10mm should be allowed between ball and lower rod.
Making bucket valve with one inch brass non-return valve
This one inch brass non return valve opened fully and allows plenty of water
to pass into the bucket.
This is probably the best and easiest to make. The 90mm class 10 pipe is cut to
the height of the valve. A very strong mix of river sand and Portland cement is
used to fill the space. After a day or two the PVC section is cut off and used to
thicken the upper wall of the bucket for handle attachment.
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Various buckets and valves
Various bucket valves being prepared together with their bucket tubes, in this
case each 500mm long.
The upper end of each bucket is thickened by adding the piece of casing used
to mould the valve, and cut to fit inside the bucket pipe and held with PVC
solvent cement. Some epoxy adhesive is added to the dried valve. The lower
end of the bucket pipe is carefully heated over a flame. The bucket pipe is then
pushed down over the bucket valve. A seal is made.
A selection of pipe lengths and valves being tested
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Drilling the tube-well
Many rigs, augers and other methods have been used to make hand
drilled shallow tube wells. The best available in Zimbabwe is called
the Vonder Rig, designed by the late Mr Erwin von Elling. This can
drill 165mm diameter holes down to depths above 20m. The same
auger bit can be fitted to simpler pipes, cross bars and used without
the work table for shallower tube-wells.
Vonder Rig in use
Also various other methods can be used where the holes drill through softer
soils and sands and at shallow depth. The hole is drilled as deep as possible
below the water table. Hand augers cannot penetrate hard rock. This subject
has been widely studied internationally and local methods used in
Zimbabwe will be dealt with in another manual.
Two types of equipment used to drill tube wells in Epworth by
the Blair Research Team in the early 1980’s.
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Using Vonder Rig auger without a work table
For shallower depths a full Vonder Rig may be unnecessary. The
excellent earth auger can be welded to a shaft which can be turned
directly by hand.
The cutters of the Vonder Rig earth auger. In this cases welded to a
shaft which can be turned by hand with a cross bar.
The soil is cut and lifted up into the auger
The cross bar is used to turn the auger. The auger is lifted when
2/3rd
full and emptied and put back into the hole.
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Fitting the PVC pipe and adding the gravel pack
Once the tube-well has been drilled as deep as is possible, the
110mm PVC casing and gravel pack are added to the drilling. If the
material is easily available, it is best to wrap a piece of stainless steel
screen around the bottom end of the pipe first. 10mm granite chips
are used as gravel packing. First a 10 litre bucket full of chips is
carefully poured down into the tube-well before the casing is
lowered. Then the casing is lowered down the tube well. This PVC
pipe is sold in 6m lengths. Joints are bonded with PVC solvent
cement. In this simplest of arrangements there are no slots made in
the casing. The aquifer water enters through the base of the PVC
pipe.
The tube well drilled. 10li of small granite chips are added to the
drilling. Then the casing is lowered on top of the granite chips placed
on the bottom of the hole
Buckets of 10mm granite are carefully poured down into the
annular space between the casing and the PVC pipe
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Now the start of the head works is built. In this case a 1.2m diameter
slab has been prepared with central hole. Using a slightly larger
diameter, a ring of bricks is laid and corbelled in slightly to hold the
slab. The slab sits on three courses of brickwork.
A plug of concrete acting as a sanitary seal then placed over the gravel
layer which comes to within 200mm of the ground level.
The space between the brickwork and the PVC pipe is now backfilled
with soil.
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Placing the concrete well slab in position
In this case a 1.2m diameter slab with a central hole (diameter about
120mm) was prepared ready to mount over the tube-well.
The PVC casing should rise above the slab by about 100mm, and is cut
at this point. The exposed casing is protected and surrounded by a
concrete ring cast within a mould made from an inverted bucket.
A flower pot is used to cover the PVC casing whilst strong concrete is
placed in the space between bucket and casing.
The outer wall of the raised head works is now plastered with
cement
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Making the water run-off and rim of the well slab
A double layer of bricks is laid as a foundation for the water run-off
channel. This should be about 3m long. Then bricks are stepped up to
the level of the slab to form a cascade arrangement which allows waste
water to flow down from the slab into the channel
The walls of the channel are combined with the walls of the slab rim
The bucket is removed and the whole unit neatly plastered and allowed
to cure. The area around the tube-well is tidied up.
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The step
When the well slab is placed several courses above the ground, a
convenience step can be built.
The step. A few bricks laid in cement mortar is all that is required
Adding chain anchor to the upper concrete ring
For units which are owned and supervised by families, experience in
the field with upgraded family wells reveals that the family itself
often decides to fit a security chain. This type of security can also be
fitted to this Bucket Pump arrangement.
While the concrete ring is still not fully cured a slot can be cut on
each side of the ring and a cut piece of chain link can be inserted
and bonded with a strong mix of concrete on each side. This
should also be allowed to cure before the unit is put to use.
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Making a l lid for tube-well
The opening of the PVC tube-well must be protected and is covered
by a lid. The lid can take several forms. Ideally the tube-well outlet
should be lockable if the unit is fitted in a family setting which is
recommended. The lid can be made in concrete using the bottom
section of a bucket as a mould. The bucket base is sawn off, two
holes punched through the base and a wire handle fitted.
A 9-10li bucket is used. The base of the bucket is used to prepare
the lid. Two holes are made and the handle of 3mm wire is
passed through as shown.
The wires are bent inwards. A 110mm casing 50mm long is cut
and the diameter reduced, being held with tape.
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The mould being prepared for concrete. A 3:1 mix of clean sharp
river sand and PC 15 cement is made and poured into the mould
and levelled. The pipe is added centrally
More concrete is then added within the pipe. This is left to cure
and harden. The ring can then be removed.
The unit is then left for a few days to cure and harden.
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The final head-works showing security chain in position
with pad locks fitted
Security chain and locks fitted. The bucket and rope (or strap as
shown in these photos) can be stored in the tube-well or in the home.
With thanks to Oswald Chakauya who helped build the demonstration
unit shown in this manual.
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Conclusions This system may mark the simplest and lowest cost option for extracting
water from shallow tube-wells. It is best suited for family use, where it can
be cared for. The bucket and valve system is cheap and easy to make. Brass
non return valves are not expensive and locally available in Zimbabwe and
90mm PVC casing costs between $4.00 -$5.00 a metre. A 500mm length is
enough to make a bucket together with an extra 50-100mm for the valve
mould and upper strengthening of the bucket. The volume of cement
required is small, and may come from the single bag of PC15 (Portland
cement) required to make the head-works. Some form of epoxy cement is
required to cement the valve block and the PVC pipe together and PVC
solvent cement. Rope may be used for raising and lowering the bucket, but
the material shown here, strong strapping, used in the transport of goods, is
popular in the rural areas of Zimbabwe. In any event the rope and bucket
should cost less than $20.00.
The system is upgradeable. First a windlass system can be added to house
the rope and make lifting easier. Such upgrades have been described in
earlier works (Technical Manual for upgrading Family Wells, 2010, Peter
Morgan and Annie Kanyemba, Aquamor. 2010). In Zimbabwe, a simple
direct action lift pump, like the Blair Pump can also be added and even a
Bush Pump, although this will be an expensive option for a family.
The most interesting feature of this concept is the flushing effect where
there is a rapid movement of water through the system which appears to
have the overall effect of increasing the quality of water delivered from the
bucket, even when it is handled. The water should be clear and taste good.
This system will be placed on field trials during 2014 in certain areas of
Zimbabwe, with bacteriological analysis being undertaken. As with all
these devices, their success can only be judged over time.
“Only time will tell!”
Peter Morgan
Harare
February 2014