Water filtration pump with disposable filter cartridges

A portable, manually-operated water filtration pump for purifying water. The pump includes an inexpensive, disposable filter cartridge which can be easily changed when the filter elements are no longer effective. The pump uses a lever to actuate a double-acting piston. The lever is collapsible to one side of the pump for compact storage. The filter cartridge is a tubular cylinder having an inner bore forming the pump cylinder. A cylindrical mechanical filter is concentric with and adjacent to the inner bore to filter out particulates larger than 0.3 microns. A fluidized granular activated charcoal filter surrounds the mechanical filter to absorb chlorine and chlorine-related compounds such as herbicides and pesticides. The pump pumps into a bottle adaptor which will fit most standard water containers. A prefilter is provided to screen out large particulates from the pump to enhance the life of the filter elements. The prefilter is weighted such that it will sink in water sources and to keep the prefilter inlet upright in still water or downstream in moving water.

BACKGROUND OF THE INVENTION 
1. Field of the invention 
This invention relates to the field of water purification units, in 
particular, portable water filtration pumps for back-country or travel use 
and other applications where manual water purification is required. 
2. Statement of the problem 
Water purification is a critical problem in today's world. While presently 
there are a large number of systems available for home and industrial 
purification, a strong need exists for a portable system of water 
purification, particularly for a lightweight, compact water filtration 
unit. Such a unit is necessary for purifying water sources for travelers, 
campers, backpackers, fishermen, hunters, rafters, in emergency 
situations, and the like. 
Water sources, even those that appear to be clear, are often contaminated. 
Water contaminants include particulate matter, chemicals, insects, 
nematodes, fungi, algae, yeasts, microorganisms, discoloration and 
radioactive contamination. The microorganisms often found in water sources 
include pathogenic microbes such as protozoa (which includes Giardia 
Lamblia), bacteria and viruses. Chemicals often found in water sources 
include chlorine, herbicides, and pesticides. 
Present portable systems for water filtration are of three types: boiling, 
chemical treatment, and mechanical filtration. Boiling water is time 
consuming and requires the need for fire. Also, boiling water will only 
kill microorganisms. It does not remove the contaminants. Chemical 
treatments, such as iodine tablets, leave an aftertaste, and may produce 
an allergic reaction with some people. Also, chemical treatments will only 
kill microorganisms and do not remove contaminants. 
Only mechanical filtration units remove the contaminants from the water. 
Typically, mechanical filtration units are of two types, passive 
filtration units and pump filtration units. 
Passive filtration systems typically use a water bag having a filtration 
system in the bottom of the bag. Water is poured into the bag which is 
then hung onto a tree or elevated structure. Water flows downward due to 
the force of gravity through the filters in the bag and into a reservoir. 
This type of system is cumbersome to transport, operates slowly and 
requires frequent replacement of the filters due to bacteria growth in the 
filters. 
There are presently several pump-type water purifiers available on the 
market. One such device is the FIRST NEED WATER PURIFIER, available from 
General Ecology, Inc. 151 Sherree Blvd, Lionville, Pa. This purifier uses 
a handle to move a pump piston vertically in a cylinder. A canister 
containing a charcoal filter is mounted parallel to the cylinder and is 
connected by plastic tubing to the cylinder. The bottom of the cylinder 
has another piece of tubing which is placed in the water source. The 
bottom of the canister has a short piece of tubing which is placed in the 
water container. Operation of the handle pumps water through the canister 
to filter the water. This system weighs approximately sixteen ounces and 
requires frequent sterilization of the filter by chlorine to prevent 
bacteria growth. The canister requires replacement at periodic intervals. 
The replacement canisters are relatively expensive. This system under 
normal usage purifies water at the rate of one quart per ninety seconds. A 
prefilter is recommended for use with this system. 
Another popular portable water purification filter is manufactured by 
Katadyn. This system uses a ceramic filter. It also uses a handle type 
pump to move water through the system. This system is expensive compared 
with other devices. 
A third commercially available water filter pump is the MSR WATERWORKS 
FILTER, manufactured by Mountain Safety Research, Seattle, Wash. This 
system uses a small, horizontally-mounted pump with a lever handle to pump 
water through an articulated urethane foam prefilter, fine mesh stainless 
steel screen, a cylinder of activated carbon and a micro-porous membrane 
cartridge having a pore size ratio of 0.1 micron absolute. This system 
screws on to a water container. This system is relatively expensive with 
expensive replacement filters. The approximate weight of this system is 20 
ounces. Other devices are known that using a separate pump and filter 
mechanism. These devices are cumbersome to operate and are relatively slow 
to filter water. 
There presently exists a need for a lightweight, compact, inexpensive water 
purification pump that operates with uniform flows at high rates with 
extensive exertion. 
Solution to the Problem 
The present invention provides a solution to these and other problems. The 
present invention provides a lightweight pump weighing approximately four 
to five ounces. 
The present invention provides a compact pump for ease of storage and 
transportation. 
The present invention provides an inexpensive pump using disposable, 
inexpensive filters capable of filtering approximately 100 gallons of 
water per filter. 
The present invention provides a pump using mechanical advantage to filter 
at a rate of 1.5 liters per minute over an elevation of 3 feet. 
The present invention provides a vertical, double-acting pump that provides 
uniform flow rates and uniform pressure rates to allow ease of operation. 
The present invention provides a prefilter to screen out large particles 
and to hold the prefilter in the water source. 
The present invention provides an adaptor for filling water containers 
without the need for holding the water containers. 
These and other features will be evident from the ensuing description of 
the invention. 
SUMMARY OF THE INVENTION 
The present invention provides a portable, manually-operated, water 
filtration pump for contaminated water. The pump uses a lever to actuate a 
piston. The lever is collapsible to one side of the pump for compact 
storage. The pump includes an inexpensive, disposable filter cartridge 
which can be easily changed when the filter elements are no longer 
effective. The filter cartridge is a tubular cylinder having an inner bore 
in which the piston is movable. 
An inlet having a screen mesh is located at the bottom of the inner bore of 
the filter cartridge. A check valve is provided adjacent the inlet to 
allow water to enter during the upstroke of the piston but prevents water 
from leaving during the downstroke of the piston. A flexible seal is 
provided on the piston which prevents water from flowing around the piston 
during the upstroke but allows water to flow around the piston during the 
downstroke. This provides a double-acting piston with uniform flow and 
uniform pressure during the pumping process. 
Water is pumped from the inner bore through a baffle into an inner plenum. 
The baffle prevents high velocity jet flow to assure a laminar flow into 
the inner plenum. The inner plenum has an annular width chosen to minimize 
pressure drops and to promote uniform flow through the filter. A 
cylindrical mechanical filter is concentric with the inner bore adjacent 
the inner plenum to filter out particulates larger than 0.1 micron. A 
fluidized granular activated charcoal filter surrounds the mechanical 
filter to absorb chlorine and chlorine-related compounds such as 
herbicides and pesticides. A screen prevents the granular activated 
charcoal from moving through the system. 
An outer plenum is provided for the treated water to exit the charcoal 
filter in a uniform flow. The outer plenum is connected through an outlet 
to a bottle adaptor which will fit most standard water containers. The 
adaptor will prevent spillage of the treated water in the container during 
the pumping process or contamination of the treated water. 
A prefilter is provided to screen out large particulates from the pump to 
enhance the life of the filter elements. The prefilter is either weighted 
on one portion or connected by an offset inlet opening to sink the 
prefilter in water sources and to keep the prefilter inlet upright in 
still water or downstream in moving water. 
The pump of the present invention is designed to be relatively inexpensive 
and uses recyclable inexpensive filters. The pump is lightweight, 
approximately 0.25 to 0.32 pounds, capable of pumping greater than 1.5 
liters per minute in normal use and is compact, about eight inches long 
with a diameter of about 2 inches. The pump is formed of lightweight 
durable components to withstand rugged use and can be easily used by one 
person. 
These and other features will become evident from the detailed description 
of a preferred embodiment taken in conjunction with the drawings.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The present invention comprises a portable, compact, lightweight water 
filtration pump which effectively filter out particles down to 0.1 to 1.0 
microns (a micron equals one-millionth of a meter). The pump of the 
present invention provides a uniform flow at rates greater than 1.5 liters 
per minute with normal usage. The pump is easily usable by one person with 
minimal exertion. This device is relatively inexpensive and uses 
inexpensive, disposable filters which are usable to purify up to 100 
gallons of water. The disposable filters are recyclable and easy to 
change. 
One possible preferred embodiment is illustrated in FIGS. 1-6. This 
description of a preferred embodiment is for explanatory purposes and is 
not meant to limit the scope of the claimed inventive concept. Other 
variations and embodiments are considered to be within the scope of the 
claimed inventive concept. 
Water filtration pump 10 of the present invention is shown in FIG. 1. Pump 
10 includes prefilter 70 and container adapter 62, both of which are 
discussed fully below. Pump 10 includes pump housing 12, as shown in FIG. 
2, having a cylindrical shape and an inner bore in which piston rod 14 is 
slidable therein. Piston 16 is formed or mounted on one end of piston rod 
14. Seal groove 18 is formed around the circumference of piston 16 as 
described below. O-ring seal 20 or another well-known type of seal is 
mounted in housing 12 allowing piston rod 14 to pass through housing 12 
while preventing water from the force of piston 16, as described below, 
from passing upward through housing 12 or contaminates from passing down 
through housing 12. Cross head 9 is affixed to the upper end of piston rod 
14. 
Lever 22 engages the upper end of piston rod 14 by slot 26 formed in lever 
22 which engages pin 28 on piston rod 14 by a resilient detent formed on 
slot 26. Lever 22 is attached to housing 12 by pivot link 24. This allows 
lever 22 to move piston 16 up and down in cartridge 30 as described below 
with a mechanical advantage. In the embodiment described, the mechanical 
advantage is three to five times. This enables the lever to exert three to 
five times the force as would the same effort moving piston 16 up and down 
without the lever advantage. 
Lever 22 is designed to be moved to a storage position when pump 10 is not 
in use. Lever 22 is unhooked from pin 28 and collapsed to one side of pump 
10 as shown in FIG. 3. This provides a compact unit for storage and 
transportation. This can be an important concern for travelers and 
backpackers who have limited space available. 
Cartridge 30 is designed to be quickly and easily attached to housing 12. 
In the described preferred embodiment, this is accomplished by a screw 
mounting attachment. Cartridge 30 is screwed into the lower portion of 
housing 12 and rotated until the mounting is secure. Seal 32 is provided 
between housing 12 and cartridge 30 to prevent leakage at the connection 
between the housing 12 and cartridge 30. The present invention is not 
meant to be limited to this descriptive embodiment but encompasses other 
variations. For instance, the cartridge may use a bayonet attachment, or a 
snap-on attachment, or other well-known attachment devices. 
As shown in FIG. 2, cartridge 30 includes a tubular plastic cylinder 34. 
Inner bore 36 is formed in cartridge 30 having an inner diameter that 
enables piston 16 to closely fit within along with a flexible seal as 
discussed below. At the lower end of inner bore 36 is an inlet 38 for 
allowing untreated water to enter into cartridge 30. A screen mesh (not 
shown) is mounted within inlet 38 to screen large particles out of inner 
bore 36. In the preferred embodiment, inlet 38 includes an extended outer 
barb 40 on which a section of tubing is attached. Inlet check valve 42 is 
mounted in inner bore 36 adjacent inlet 38. Inlet check valve 42 is a 
cantilevered reed valve which allows water to enter cartridge 30 but 
prevents water from exiting through inlet 38. The operation of inlet check 
valve 42 is discussed below. 
Inlet 44, shown in FIGS. 4 and 5, is formed at the upper end of inner bore 
36 leading into inner plenum 46. Inner plenum 46 surrounds inner bore 36 
and is critically sized as discussed below. Baffle 48 is formed in inlet 
44 to prevent high jet velocity flow into inner plenum 46 and to provide 
laminar flow from inner bore 36 into inner plenum 46. Adjacent inner 
plenum 46 is mechanical filter 50. Mechanical filter 50 is a borasilicate 
cylinder, or a plastic membrane cylinder, or a porous plastic tubular 
cylinder having pores filtering out particles having a size greater than 
0.1 to 1.0 microns from exiting the pump. In the preferred embodiment, 0.3 
microns is used as the filter size. This size effectively filters most 
particle contaminates that may feasibly be filtered. Mechanical filter 50 
is sealed at the top against seal 32 and at the bottom against lower end 
400 of filter cartridge cylinder 30 by mechanical interference. 
Granular activated carbon bed filter 52 surrounds mechanical filter 50. 
Granular activated carbon bed filter 52 is a tubular cylinder formed from 
fluidized granular activated charcoal with a particle size to maximize 
absorption of chlorine, chlorine-related products and other chemicals, 
such as herbicides and pesticides. The fluidized granular activated 
charcoal provides an efficient absorption rate with a low pressure drop. 
In the preferred descriptive embodiment, fluidized granular activated 
charcoal filter 52 filters approximately one hundred gallons of water. 
The lower end of fluidized granular activated charcoal filter 52 is sealed 
by mechanical interference against lower end 400 of filter cartridge 30. 
Outer plenum 54 is formed at the upper end of filter 52. Outer plenum 54 
is in the shape of an annular ring formed around the top of fluidized 
granular activated charcoal filter 52. Outlet 56 is connected to outer 
plenum 54 and includes a hose barb 58 for attachment to a section of 
tubing as discussed below. 
Flexible seal 60 is mounted within groove 18 of piston 16 as illustrated in 
FIGS. 2, 4 and 5. Seal 60 is formed from an elastomer or an elastomer-like 
thermoplastic. Seal 60 is such, that when mounted within groove 18 (FIG. 
2) of piston 16, piston 16 is double acting to provide uniform flow and 
pressure during both the upstroke and downstroke of piston 16. Seal 60 has 
an accordion-like, flexible lip that moves toward the wall of inner bore 
36 during the piston upstroke so water above piston 16 is forced around 
the top of inner bore 36 and through baffle area 48 (FIG. 4) and into 
inner plenum 46. At the same time, water is being drawn upward through 
inlet 38 and through the open inlet check valve 42 as shown in FIG. 4. The 
outer lip of seal 60 moves away from the wall of inner bore 36 during the 
downstroke of piston 16 by the force of the water as shown in FIG. 5. The 
water below piston 16 is forced downward, thus closing cantilevered reed 
check valve 42 or similar valve to force the water upward around piston 16 
and by seal 60 as shown in FIG. 5. 
The use of a double-acting piston provides a uniform flow rate giving a 
uniform pressure drop. Double-acting piston 16 minimizes the pressure drop 
to provide a uniform flow rate. This reduces the force necessary to 
operate the pump and reduces the potential of damage to the filter 
elements and to the pump. 
The internal volume of inner bore 36 and the dimensions of piston rod 14 
are chosen so the volume of water displaced during the upstroke of the 
piston is equal to the volume of water displaced during the downstroke of 
the piston to further assure uniform flow and minimal pressure drop. The 
water displaced in the downstroke is equal to the volume of the inner bore 
36 minus the volume of piston rod 14. The water displaced in the upstroke 
is equal to the volume of piston rod 14. Therefore, the volume of piston 
rod 14 must equal the volume of inner bore 36 minus the volume of piston 
rod 14. The dimensions of piston rod 14 and inner bore 36 can thus be 
varied to achieve the desired dimensions. 
The dimensions of inner plenum 46 are also chosen to minimize pressure 
drops and to provide uniform flow through pump 10. Inner plenum 46 is 
designed as an annulus around inner bore 36 with a width t between the 
range of 0.02 to 0.05 of the diameter of the entire filter and a length 
Lp. A width smaller than this range creates a high pressure drop in inner 
plenum 46. A width greater than this range causes non-uniform flow through 
the filter creating high pressure drops in the filter. Outer plenum 54 is 
sized to provide uniform flow out of the filter as well. 
Outlet barb 56 (FIG. 2) is connected to a section of tubing 58, illustrated 
in FIG. 1, leading to water container adaptor 62. Adaptor 62 is designed 
to closely fit within the openings of most standard water containers. As 
shown in FIG. 1, adaptor 62 has a first section 64 to fit smaller openings 
and a second section 66 to fit larger openings. This allows hands free 
operation of the device without having to hold the water container being 
filled. The fit of adaptor within the water container opening is such that 
should the water container tip or fall over, treated water will not spill 
out and contaminates will not enter the water container. Adaptor 62 can 
also be designed to screw into the openings of the water containers. 
Tubing 58 can be clamped or bonded onto outlet hose barb 56 and onto 
adaptor 62 if desired. 
Cartridge inlet 38, as illustrated in FIG. 2 is connected to prefilter 70 
(FIG. 1) by tubing 72. If desired, tubing 72 can be securely attached by 
clamps or bonding to inlet 38 over hose barb 40 and to prefilter 70 over 
hose barb 74 shown in FIG. 6. Typically, a 0.25 to 0.38 inch internal 
diameter elastomer or plastic tubing is used at a length up to 3 feet 
long. Prefilter 70 is dropped into a water source to filter out large 
particle contaminates down to 70 to 120 microns in size. Pump 10, under 
normal usage, is able to "pull" water easily at least through an elevation 
of 3 feet. This allows the user to comfortably operate the pump without 
kneeling or actually getting into the water source. 
As illustrated in FIG. 6, prefilter 70 has a semi-spherical-shaped lower 
portion 76. Upper portion 78 is attached to lower portion 76 by living 
hinge 80 and snap-lock 82 so that upper portion 78 can be easily opened to 
clean prefilter 72. Inlet opening 84 having a molded or woven or metal 
mesh screen with 0.01 to 0.02 millimeter pore size, is formed in upper 
portion 78. Filter screen 88 is mounted in the interior 90 of lower 
portion 76 formed of either metal or plastic and filtering particles 
larger than 100 to 150 microns. Outlet 92 is formed on upper portion 78 at 
a location approximately one-third the radial length of the prefilter. 
Water is drawn by pump through inlet screen 84 down through filter screen 
88 into the interior 90 and out through outlet 92 up through tubing 72 
into inlet 38 of cartridge 30 of pump 10. The prefilter screens large 
particle contaminates from pump 10 to increase the life of disposable 
cartridges 30. Upper portion 78 (FIG. 6) can be unsnapped to clean each of 
the filters 86 and 88 as necessary. 
Weighted portion 94 is molded, formed or attached to lower portion 76 of 
prefilter 70. Weighted portion 94 can be attached to only a portion of 
lower portion 76 as shown in FIG. 1 or be attached to the entire lower 
portion 76 as shown in FIG. 6. Weighted portion 94 accomplishes three 
functions. First, prefilter 70 sinks in moving and still water beneath the 
surface of the water source. The majority of contaminates typically float 
on the surface, thus by sinking below the surface, prefilter 72 misses the 
surface contaminates. Second, in still water, prefilter 70 is held with 
inlet opening 84 in an up position to prevent bottom dirt from being 
pulled into prefilter 70. Third, weighted portion 94, or the offset 
location of the hose barb, moves the center of gravity of prefilter 70 to 
one side. In moving water, this will cause weighted portion 94 to move 
downstream first, thus tilting upper portion 78 and inlet opening 84 in 
the downstream position. This prevents waterborne large particles from 
flowing into inlet opening 84 and reducing clogging of prefilter 70. 
Prefilter 70 is designed to be small, lightweight, inexpensive and to 
create an insignificant pressure drop to allow uniform flow through pump 
10. In the descriptive preferred embodiment, prefilter 70 has an outer 
diameter of less than 1.75 inches and a pressure drop of less than 0.25 
psi at a flow rate of 1.2 quarts per minute. 
Cartridge 30 is adapted to be fitted with additional pre-conditioning or 
post-conditioning units for further purification of water. For instance, 
as illustrated in FIG. 7, pre-conditioning unit 96 is attached to the 
lower end of cartridge 30 by a screw-on attachment 98. Pre-conditioning 
unit 96 contains an iodine-coated resin bed to kill viruses, bacteria, and 
the like which are too small to be filtered out. Fluidized granular 
activated charcoal filter 52 then filters out the iodine compounds from 
the water. 
In one embodiment, pump 10 is designed for lightweight, compact storage for 
use in travel or backpacking. Pump 10 has an overall length with lever 22 
in storage position of about eight inches with filter cartridge 30 having 
a two inch diameter and a five inch length. The overall weight is 0.25 to 
0.32 pounds. Pump 10 filters water under normal usage at a rate greater 
than 1.5 liters per minute. Cartridge 30 will last for approximately 100 
hundred gallons under normal usage. Cartridge 30 is inexpensive and easily 
replaced after filters 50 and 52 are no longer effective. Also, cartridges 
30 may be replaced after periods of non-use in order to prevent the 
effects of bacteria growth if the filters were not sterilized after use. 
The used filter cartridges are designed to be recyclable. These design 
parameters are for descriptive purposes. Other sizes and designs are 
considered to be encompassed by the claimed invention. 
Pump 10 and the housing of cartridge 30 are formed from polycarbonate or 
nylon 616 with lever 22 formed from glass-filled polycarbonate or nylon 
616 to be lightweight yet durable. Mechanical filter 50 is formed from 
borasilicate, or porous plastic to be durable. Previous devices using 
silver impregnated ceramic tended to be fragile, with some fear of the 
effect of silver impregnation on drinking water. The use of fluidized 
granular activated charcoal provides a more efficient absorption with a 
lower pressure drop than many charcoal filters. The above description is 
for explanatory purposes and is not meant to limit the invention as 
claimed. Other materials, pump designs and filter designs are considered 
to be within the claimed inventive concept. 
Weighted prefilter 70 and water container adaptor 60 allows pump 10 to be 
used by a single person without the need for additional assistance or 
contortions in filtering from a stream or other water source. Lever 22 
provides a mechanical advantage to greatly increase the efficiency of the 
pumping action at an easy exertion rate. These features combine to provide 
an efficient water purification device that is easily operated. 
In operation, pump 10 is transported with lever 22 in the storage position 
as shown in FIG. 3. When it is desired to purify water from a water 
source, lever 22 is unfolded and moved into the operating position where 
slot 26 engages pin 28 of piston rod 14 (FIG. 1) Water container adaptor 
62 (FIG. 1) or 620 (FIGS. 17, 18 or 19), is inserted into the opening of a 
water container. Prefilter 70 (FIG. 6) is dropped into the water source. 
Lever 22 is operated up and down to pump water from the water source 
through prefilter 70 and into pump 10. The water is moved by double-acting 
piston 16 through mechanical filter 50 to remove particulate 
contamination, then through carbon-bed filter 52 to remove chemical 
contamination. The water is then pumped through outlet 56 and into the 
water container. After approximately 100 gallons has been pumped or after 
extended periods of non-use of the pump, cartridge 30 can be quickly and 
easily replaced by a new cartridge. The old cartridge is then able to be 
recycled. 
A second possible preferred embodiment is illustrated in FIGS. 8 and 9. 
This embodiment operates similar to the above-described embodiment. As 
illustrated in FIG. 8, an inner pump cylinder 100 is formed on pump 
housing 12. Inner pump cylinder 100 includes threaded attachment 102 which 
mates with threaded attachment 104 on cartridge 30. Cartridge 30 has an 
inner mechanical filter 50', identical to filter 50 described above, 
carbon bed filter 52', identical to carbon bed filter described above, lip 
802 similar to lip 502 of FIG. 5, and outlet plenum 54' attached to outlet 
56' both similar 54 and 56 described above. 
Inner pump cylinder 100 includes an inlet opening 38' which opens through 
inlet valve 42 into inner pump cylinder 100. O-ring 106 is mounted near 
the bottom of inner pump cylinder 100 adjacent inlet opening 38' and barb 
40'. Inner pump cylinder 100 has a thin-walled casing 108 in which piston 
16 is movable. Seal 60 interacts with inlet valve 42 to provide the 
double-acting performance described above. 
Pressure relief valve 110 is also illustrated in FIGS. 8 and 9. Pressure 
relief valve includes radial hole 112 formed in piston rod 14 above piston 
16. Longitudinal passage 118 is formed in piston rod 14 communicating with 
radial hole 112 and an opening formed at the top of piston rod 14. Spring 
114 is inserted in radial hole 112 biasing ball 116. The bias is selected 
so that when pressure builds up in pump cylinder, from clogging of the 
inlet or outlet openings or other causes, ball 116 is forced inward 
against spring 114 to allow water to flow up through passage 118 and out 
of the pump to relieve the pressure build up. 
Inner pump cylinder 100 is easily assembled onto pump housing 32 by 
screwing the threaded elements 102 and 104 together. O-ring sealing ring 
106 seals the lower portion of inner pump cylinder 100 against lower 
portion 120 of the cartridge housing (FIG. 8). Inner plenum 900 (FIG. 9) 
comprises the space between the outer wall 801 of inner pump cylinder 100 
and the inner wall of mechanical filter 50'. The baffle 44 (FIG. 9) works 
similar as above to create uniform, laminar flow into the filters. The 
pump works as did the earlier described embodiment to provide uniform 
pressure and flow through the pump. The second embodiment allows a more 
inexpensive filter cartridge to be used, since the inner pump cylinder 
remains with the pump housing. The pre-filters and water container 
adaptors are usable with both embodiments. 
The present invention provides a lightweight, compact, inexpensive 
filtration unit that is easily used. The claimed invention is not meant to 
be limited by this description. Other embodiments and variations are 
considered to be within the inventive scope of the claimed invention.