WO1991000765A1

WO1991000765A1 - Apparatus for sensing the presence of a conductive liquid in a non-conductive liquid

Info

Publication number: WO1991000765A1
Application number: PCT/US1990/003874
Authority: WO
Inventors: Jack L. Taylor
Original assignee: Taylor Jack L
Priority date: 1989-07-13
Filing date: 1990-07-13
Publication date: 1991-01-24
Also published as: AU6290990A

Abstract

An apparatus for sensing the presence of a conductive liquid in one or more containers (12) for containing a substantially non-conductive liquid (20) and discharging the conductive liquid (22) from the one or more containers. The conductive liquid has a higher specific gravity than the non-conductive liquid. The apparatus includes a submersible pump (24) disposed in each one of the one or more containers for pumping liquid from near the bottom of the container. The submersible pump includes an inlet (26) proximate the bottom of the container and an outlet (27). A sensor (29) is provided disposed in each one of the one or more containers for sensing the presence of conductive liquid in the container. The sensing means is disposed proximate the submersible pump. An alarm is operably connected to the sensing means for energizing when the sensing means detects the presence of conductive liquid in at least one of the one or more containers. A pump energizer energizes the pump when the sensing means detects the presence of conductive liquid in the container.

Description

Apparatus for Sensing the Presence of a Conductive Liquid in a Non-Conductive Liquid

Background of the Invention Technical Field

The present invention relates to apparatuses and methods for detecting the presence of a conductive liquid in the presence of a non-conductive liquid in a storage tank and discharging the conductive liquid from the tank. Background Art

The presence of a conductive liquid, such as water, in a tank of a non-conductive liquid, such as a fuel, can be an aggravating and expensive problem to solve. Moreover, the presence of water in the fuel tanks of aircraft, can lead to engine failure, with its concomitant catastrophic consequences.

The current approved procedure of checking for water in an airplane's fuel tanks consists of draining a few ounces of fuel from the tank's sump into a sample vial and looking for water in the bottom of the vial. This method is crude at best and, at worst, misleading. When there is a small percentage of water in a sample vial of fuel, the water can be easily visually perceived. In situations where the contamination of the fuel by water is extreme, however, the sample vial can conceivably be completely full of water. Given the small volume in the sample vial, a full sample vial of water is similar in appearance to a full sample vial of fuel. A pilot moving quickly around the airplane during a pre-flight check can easily believe that the sample vial is full of fuel rather than water. A pilot thus mislead will believe there is no water in the fuel and will proceed to operate the airplane with an unsafe amount of water in the fuel tanks. Moreover, many pilots may test their fuel durin preflight, then fill the tanks with fresh fuel and take off without ever checking the new fuel added to the tanks. With the current method of testing fuel for water contamination using a sample vial as described above, fuel cannot be tested during flight, only on the ground during a pre light check. Thus, a pilot is denied a test as to the integrity of the aircraft's fuel supply when it is most critical*—._^during flight.

Another technique that can be used to keep water from the engine is to employ a water/fuel separator disposed in the fuel line between the fuel tank and the engine to separate water from the fuel and then discharge the water, passing only fuel to the engine. These water/fuel separators are fairly effective but require routine inspection to insure that they do not fill up and pass water on to the engine. In addition, water/fuel separators have the added shortcoming of being ineffective when only water, and no fuel, is present in the fuel liie.

Disclosure of the Invention

The present invention overcomes the problems and disadvantages of the prior art by providing an apparatus for sensing a conductive liquid in a tank containing a non-conductive liquid and subsequently discharging the conductive liquid from the tank.

In a preferred embodiment, an apparatus in accordance with the present invention can alert an operator that there is water contamination in the fuel tank and also discharge the water from the fuel tank and/or remove the water to a holding tank to avoid the possibility of it passing to the engines. Thus, the apparatus of the invention can remove water from the fuel tank and eliminate the water problem at the tank instead of allowing water into the fuel lines and then trying to separate it out. It should be noted that for additional safety, a fuel/water separator may be installed in a fuel line in combination with the apparatus with the invention.

An apparatus in accordance with the present invention is equally effective in application to diesel fuel tanks where water contamination of the fuel might not present a potentially fatal situation, but can be very costly to the user of such fuel. The apparatus of the invention may also find application in tanks for storing any type of non- conductive liquid, such as, for example, hydraulic fluid, kerosene, alcohols, heavy oil, and large volumes of gasoline or other fuels. Each of these types of tanks for storing non-conductive liquids present potential problems wherein water can collect through condensation or by other means.

Accordingly, it is an object of the present invention to provide a reliable means for detecting a conductive liquid, such as, for example, water, in any type of container for storing any type of non-conductive liquid, such as a fuel or oil.

It is a further object of the present invention to provide a means for removing conductive liquid that has been detected from non-conductive liquid in a container.

Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, an apparatus is provided for sensing the presence of a conductive liquid in one or more containers for containing a substantially non-conductive liquid and discharging the conductive liquid from the one or more containers, the conductive liquid having a higher specific gravity than the non-conductive liquid, comprising: a submersible pump disposed in each one of the one or more containers for pumping liquid from near the bottom of the container including an inlet proximate the bottom of the container and an outlet. The apparatus further comprises sensing means - 4 -

disposed in each one of the one or more containers for sensing the presence of conductive liquid in the container. The sensing means are disposed proximate the submersible pump.

Alarm means are provided operably connected to the sensing means for energizing when the sensing means detects the presence of conductive liquid in at least one of the one or more containers. Pump energizing means energize the pump when the sensing means detects the presence of conductive liquid in the container.

Brief Description of the Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and, together with the description, serve to explain the principles of the invention. Like parts or components in the drawings are identified by the same reference numbers.

Figure 1 is a block schematic diagram of an apparatus fo,r sensing the presence of a conductive liquid in a non-condu tive liquid in a container and discharging the conductive liquid from the container in accordance with the present invention;

Figure 2 is a side view of a sensing means in accordance with the present invention;

Figure 3 is a bottom view of a sensing means in accordance-with the present invention;

Figure 4 is an electrical schematic diagram of an electrical circuit useful in an apparatus in accordance with the present invention;

Figure 5 is an electrical schematic diagram of a portion of the electrical circuit of Figure 4 for detecting and indicating the presence of a conductive liquid in a non- conductive liquid in accordance with the present invention;

Figure 6 is a perspective view of a control panel useful in agp. apparatus in accordance with the present invention; and Figure 7 is a perspective view of a storage container employing sensing means in accordance with the present invention.

Best Mode for Carrying Out the Invention

Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. The preferred embodiment of the conductive liquid sensing and discharging apparatus of the present invention is shown in Fig. 1 and represented generally by the numeral 10. An apparatus in accordance with the present invention is for sensing the presence of a conductive liquid in one or more containers for containing a substantially non-conductive liquid and discharging the conductive liquid from the one or more containers. As shown in Fig. 1, a container 12 is provided having side walls 14, a top wall 16 and a bottom wall 18. The container 12 may be of any desired shape. Thus, the side walls 14 may, for example, define a circular, square, or rectangular enclosure. The top wall 16 and bottom wall 18 are joined to the side walls 14 in any desired fashion to seal the container 12 so that liquid contained therein cannot escape. If desired, a pressure relief valve or vent (not shown) may be provided in, for example, top wall 16 of container 12 to prevent the build up of excessive pressure within container 12.

The container 12 contains a substantially non- conductive liquid 20 and may contain a substantially conductive liquid 22 as shown in Fig. 1. Substantially non- conductive liquids 20 to which the present invention may be applied include, but are not limited to, gasoline, petroleum oils, kerosene, and alcohols, for example. As described herein, conductive liquids are, for example, water, pure or contaminated, but need not be so limited as any conductive liquid may be detected and discharged by an apparatus in accordance with the present invention. For the purposes of the present invention the terms "conductive" and "non- conductive" liquids refer to such liquids that can be electrically distinguished from each other. Preferably, a "conductive" liquid is one having a resistance of substantially 0 to 10Ok ohms and a "non-conductive" liquid is one having a resistance in excess of substantially 100k ohms.

The conductive liquid preferably has a higher specific gravity than the non-conductive liquid which allows the two types of liquids to be spatially separated from one another by the force of gravity. Other techniques may be employed, however, to spatially separate the conductive liquid from the non-conductive liquid and then detect the presence of the conductive liquid. Such techniques are considered to be within the scope of the present invention.

An'apparatus in accordance with the present invention includes a submersible pump disposed in each one of the one or more containers for pumping liquid from near the bottom of the container including an inlet proximate the bottom of the container and an outlet. As shown in Fig. 1, a submersible pump 24 is provided disposed in container 12. Submersible pump 24 is disposed near the bottom 25 of the interior of container 12 such that pump inlet 26 is disposed proximate the bottom 25 of the interior of container 12. Submersible pump 24 includes an outlet 27 and has a pair of power leads* 23 to provide power to operate submersible pump 24. The source of the power provided by the pair of power leads 23 to? operate submersible pump 24 is more fully explained below. A suitable submersible pump for use in an apparatus in accordance with the present invention has been found to be a model 1EP68 pump made by the AC Sparkplug Division of*the General Motors Corporation of Flint, Michigan 40556.

Am apparatus in accordance with the present invention includes sensing means disposed in each one of said one or more containers for sensing the presence of conductivt liquid in the container. Preferably, the sensing means in an apparatus in accordance with the present invention is disposed proximate the submersible pump. As shown in Fig. 1, a sensing means 29 is provided disposed proximate the submersible pump 24. A sensing means 29 in accordance with the present invention is shown in side view in Fig. 2 and in bottom view in Fig. 3.

Preferably, the sensing means includes a pair of spaced-apart probes, the circuit between the spaced-apart probes being capable of being completed by water to energize the alarm means. Sensing means 29 includes two spaced apart probes 38 each having an associated signal lead pair 36. Preferably, the probes include gold plated zinc probes.

Preferably, as illustrated in Fig. 2, sensing means 29 includes a nipple 31 within which the spaced apart probes 38 are mounted. Also preferably, spaced apart probes 38 are potted in place in nipple 31 by, for example, an epoxy resin. Sensing means 29 also preferably includes a nut 33 in threaded engagement with the external threads of nipple 31. A lock nut 35 is also preferably provided to lock nut 33 in a desired position along nipple 31.

Preferably, the apparatus of the present invention includes a. mounting plate for mounting the submersible pump in close proximity to the sensor means. As shown in Fig. 1, a mounting plate 35 is provided to which submersible pump 24 is mounted. Sensor means 29 is also preferably mounted to mounting plate 35. Preferably, an apparatus in accordance with the present invention includes means to adjust the position of the sensor means relative to the bottom of the container. When sensor means 29 is mounted to mounting plate 35 through nut 33, nipple 31 can be rotated which, because of the threaded engagement between nipple 31 and nut 33, causes nipple 31 to move relative to nut 33 and mounting plate 35 toward or away from bottom 25 of container 12. In this way, the position of nipple 31 and, hence, spaced apart probes 38, can be altered relative to the bottom 25 of container 12. By changing the relative position of spaced apart probes 38 and bottom 25 of container 12, the level of conductive liquid 22 allowed within container 12 before its detection can be changed. Specifically, the greater the distance between spaced apart probes 38 and the bottom 25 of container 12, the higher the level of conductive liquid 22 before its presence is detected by spaced apart probes 38 in the manner described below.

The presence of a conductive liquid 22 in the container 12 of Fig. 1 can be detected by a circuit shown in Fig. 4, for example. The specific circuit and the characteristics of its individual components is provided as an example only and is not intended to limit the present invention to the specific example or embodiment shown.

When switch 26 is closed, the conductive liquid detection system will begin operation by connecting the power supply 65 with the remainder of the system, as described below. Current will pass through fuse 28 which will limit the amount of current being drawn to 1 amp. Switch 26 is, preferably, an illuminated switch which acts as a system on/ off control and on/off indicator. Thus, if a wiring fault should occur, switch 26 will not illuminate when depressed to alert the operator that the entire system is non-operational. Fuse 28 should then be checked and if fuse 28 is not blown the operator will know that the power supply to the system has been disrupted.

From switch 26, the current passes to 12 volt regulator 30. Regulator 30 is placed in the circuit to ensure that the voltage supplied to the circuit beyond regulator 30 is limited to 12 volts. Regulator 30 allows this system to be used with a power supply 65 that supplies power in the range of from 12 volts to 35 volts. A 5v regulator 32 is provided wherein the voltage supplied by regulator 30 will be reduced to 5 volts on the output side of 5v regulator 32. This is the voltage supplied to sensing means 29.

In route to sensing means 29, the current passes through a 4.7k ohm resistor 34, the function of which is explained more fully below. At node B shown in Fig. 4, the 5 volts from regulator 32 are shared across as many outgoing conductors 31 as there are sensing means 29. This number of sensing means 29 is determined by the number of containers or locations in which the presence of a conductive liquid is to be identified. Thus, as illustrated in Fig. 4, for a circuit serving two sensing means 29, preferably disposed in two separate containers 12, two outgoing conductors 31' and 31" are required as output to the sensing means 29 disposed in a first container (not shown) and a second container (not shown), respectively. While the first and second containers are not shown in Fig. 4, it is understood that they correspond in structure and function to container 12 shown in Fig. 1, for example.

From node B, voltage will be present through outgoing conductor 31 at one of the spaced apart probes 38. If no water connects probes 38, one probe will have a maximum of 5 volts while the other probe will remain at 0 volts. Once water contacts both probes 38 and is present between them current will pass from the probe with the 5 volts to the probe with 0 volts. Then current will travel back to the control circuit on an incoming conductor 33, through resistor 40, and into the base of transistor 42. The signal lead pair 36 from sensing means 29 described in reference to Fig. 1 preferably includes an outgoing conductor 31 and an incoming conductor 33.

Resistors 34 and 40 act to reduce the amount of current allowed to sensor means 29 and transistor 42. Even though typical water has a resistance in the range of 100K ohms, we will consider the resistance of the water to be 0 ohms. This will represent a "worst case" situation. Another assumption that must be made is that a silicon transistor is being used with a voltage drop between base and emitter of 0.7 volts. With these assumptions, the current passing between probes 38 when the resistance of the water between the probes 38 is assumed to be 0 ohms can be calculated as:

I max = (5v-0.7v)/(4.7k ohm + 0 ohm + 4.7k ohm)

I max = 457 micro amps

The level of I max is made sufficiently low so as to preclude the possibility of starting an accidental fire or /00765 PCT/US90/0

- 10 -

explosion within container 12 in the presence of a non-conductive liquid 20.

A apparatus in accordance with the present invention includes alarm means operably connected to the sensing eatis for energizing when the sensing means detects the presence of conductive liquid in at least one of the one or more containers. Once current flows between spaced apart probes 38 due to the presence of conductive liquid between them, the voltage present at the base of transistor 42 will cause transistor 42 to conduct between its collector and emitter. A path to ground 50 will then be made from the 12 volt regulator 30 through resistor 52 and light-emitting- diode (LED) 54 to ground and also from 12 volt regulator 30 through the 12 volt buzzer 56 and diode 58 to ground. This part of the circuit will alert the operator that he has a water in fuel problem.

As demarcated in dotted outline in Fig. 4, the circuit is provided with two separate alarm means circuits 57' and 57", each alarm means circuit 57' and 57" corresponlipg to a sensing means 29 disposed in a first container and a second container, respectively. In this way, an operator can determine which of the first or second containers are contaminated with conductive liquid. Specifically, only sensing means 29 in which the spaced apart probes 38 are in contact with conductive liquid will illuminate its corresponding LED 54.

It should be noted that the buzzer 56 is common to both of first and second alarm means circuits 57' and 57", respectively. Thus, buzzer 56 will audibly alert the operator to the -existence of a problem while LED 54 that is illuminated will identify the location of the problem as being in the first or second container or, possibly, in both containers if both LED 54's are illuminated. If preferred by the operator, an LED 54 can be used without buzzer 56 to indicate the presence of an undesirable amount of conductive liquid in container 12 visibly but not audibly. Any combination of audio and visual warning devices should be considered well within the scope of this invention. It is preferable that the at least one container includes more than one container and the alarm means is energized by a signal from one of said sensors. Thus, the buzzer 56 will sound an audible alarm when any one of sensor means 29 detects the presence of a conductive liquid in any one of the containers.

As shown in Fig. 4, and explained above, the present invention contemplates locating sensing means 29 in more than one container 12. While one embodiment of the present invention has been described above in reference to Fig. 4 wherein sensing means 29 are provided in two containers, it is possible for the circuit of Fig. 4 to accommodate more than two sensing means 29 in the manner illustrated in Fig. 5. Specifically, for each additional sensing means 29, additional Ik ohm resistors 52, LED 54, diode 58, transistor 42, 4.7k ohm resistor 40, and diodes 41 are provided connected in the manner described above in reference to Fig. 4.

Thus, by use of a sensing means 29 having dual probes 38, a path of electrical continuity is provided through any conductive liquid that might be present and in contact with probes 38 of sensing means 29. This conductive liquid completes a circuit in the control unit that activates a warning light and buzzer to alert the operator of contamination and show the operator in which container the problem exists.

An apparatus in accordance with the present invention includes pump energizing means for energizing the pump when the sensing means detects the presence of conductive liquid in the container. The operator may then activate submerged pump 24 to discard the conductive liquid into a storage tank for later disposal. As shown in Fig. 4, a pump switch 60 that corresponds to the LED 54 that is illuminated may be depressed. It should be understood that while only one pump switch 60 is shown in Fig. 4, a first and - 12 -

second pump switch 60 ^■ and 60", respectively, will be provided for each submersible pump 24 disposed in each of the first and second containers, respectively. In that way, each pump may be individually energized depending upon whether an excess amount of conductive liquid is detected in a first container o a second container.

Preferably, the pump energizing means includes a power source and a switch in series between the power source and the pump such that closing the switch connects the pump and the power source to energize the pump and to cause the pump to operate to take water into the intake and discharge it from the outlet thereof. As shown in Fig. 4, by depressing pump switch 60, a path for current from the 12 volt regulator 30 through the holding coil 62 of relay 64 to ground is provided. This action causes contacts 66 of relay

64 to close and create a path for current from power source

65 through the 5 amp circuit breaker 68 and to submersible pump 24 that will energize submersible pump 24 and cause it to pump the conductive liquid from container 12 to a storage container 67, as shown in Fig. 1, for later disposal. Resistor 70 acts only as a means for ensuring that relay 64 does not try to engage until switch 60 is depressed. It should be noted that the action of switch 60 can be automated such that a^■'desired submersible pump 24 is engaged when conductive liquid is detected in a container in which the submersible pump 24 is disposed.

Preferably, the apparatus of the present invention includes test means for testing the integrity of the audible and visible alarm. As shown in Fig. 4, a test switch 72 is provided to"evaluate the condition of LED's 54 and buzzer 56. By depressing and holding test switch 72, the operator will see the illumination of each LED 54 and hear buzzer 56 to test their integrity.

Fig. 6 shows a control panel 90 useful in an apparatus in accordance with the present invention. Having reference also to Fig. 4, an example of the relative locations at switches, fuses and alarm means in an apparatus in accordance with the present invention is shown. Specifically, on/off switch 26, test switch 72 and first and second pump switches 60' and 60", respectively, corresponding to switches for submersible pumps 24 disposed in first and second containers, respectively, are shown. Further, LED 54' and LED 54" to indicate the presence of conductive liquid in first and second containers, respectively, are shown as is buzzer 56. Further still, storage container full LED 54"', more fully described below, is shown.

Preferably, an apparatus in accordance with the present invention includes a discharge outlet and means to place the discharge outlet in fluid communication with the outlet of the submersible pump. As shown in Fig. 1, a discharge outlet 72 is provided to discharge conductive liquid, pumped by submerged pump 24, into storage container 67.

Preferably, the means to place the overflow outlet in fluid communication with the outlet of the submersible pump is a conduit. As shown in Fig. 1, a conduit 74 is provided that extends from the outlet 27 of the submersible pump 24 to the discharge outlet 72 to place the two outlets in fluid communication. In this way, conductive fluid pumped from the inside of the container 12 is directed through conduit 74 from submersible pump 24 to storage container 67.

As shown in Fig. 1, a second conduit 80 may be provided between the mounting plate 35 through top wall 16 of container 12. The first conduit 74, pump power leads 23, and signal lead pair 36 are routed through second conduit 80. Second conduit 80 at least passes through top wall 16 of container 12 and is held in place by a nipple 82, which is attached to the external surface of conduit 80, and a flange 84 which is attached to the top wall 16 and to nipple 82.

As shown in Fig. 7, another sensing means 29 can be placed in storage container 67 to alert the operator that it should be drained into an approved disposal site. Since a small portion of the non-conductive liquid will be discarded with the conductive liquid, sensing means 29 in storage container 67 will be placed so that the signal will alert the operator when the container is approximately 2/3 full of conductive liquid. This margin should account for the non- conductive liquid above the conductive liquid that will not be detected by the sensing means. The position of sensing means 29 is held at the desired position by nipple 91 affixed to a top 89 of storage container 67 by flange 93. Sensing means 29 is fixed to one end of nipple 91 and nipple 91 is fixed at the distal end thereof to flange 93.

The presence of conductive liquid is detected by sensing means 29 in the manner described above in reference to the sensing means shown in Figs. 2 and 3. Further, signal lead pair 36' communicates with an alarm means circuit 57'", alarm means circuit 57'" having the structure and function as fiEst and second alarm mean circuits 57' and 57", respectively, described above in reference to Fig. 4. Thus, when the conductive liquid has reached the desired level, 3/4 full as shown in Fig. 7, for example, an LED 54"' is illuminated to indicate that the conductive liquid has reached this level. At his point, the operator will know that it is time the storage container 67 was emptied of its contents.

To accomplish the emptying of its contents, storage container 67 includes a bottom portion 90 including a stopcock 92 that, when opened, allows liquid stored in storage container 67 to be discharged by the force of gravity through line 94.

Sensor means 29 may be placed alone in locations that would not be appropriate for submersible pumps 24. In this situation, the operator would be required to dispose of the water contamination in another manner. An example of this situation would be storage container 67 shown in Fig. 7. Since this is a contaminated liquid storage container, there is no need for a pump since there is nowhere to pump its contents on the aircraft or vehicle. The LED 54"' that indicates that storage container 67 needs draining at an approved location would only alert the operator of this condition.

It will be apparent to those skilled in the art that various modifications and variations can be made in the apparatus of the present invention without departing from the scope or spirit of the invention. For example, any number of sensors or pump/sensor combinations can be used to fit any specific situation. Pump/sensor combinations are primarily intended for tanks of any type, while sensors alone can be used in fuel/water separators, containers such as tanks, or any other location deemed necessary. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

E S EET

Claims

1. An apparatus for sensing the presence of a conductive liquid in one or more containers for containing a substantially non-conductive liquid and discharging the conductive liquid from the one or more containers, the conductive liquid having a higher specific gravity than the non-conductive liquid, the apparatus comprising: a submersible pump disposed in each one of said one or more containers for pumping liquid from near the bottom of the container including an inlet proximate the bottom of the container and an outlet; sensing means disposed in each one of said one or more containers for sensing the presence of conductive liquid in the container, said sensing means being disposed proximate the submersible pump; alarm means operably connected to the sensing means for energizing when the sensing means detects the presence of conductive liquid in at least one of the one or more containers; and pump energizing means for energizing the pump when the sensing means detects the presence of conductive liquid in the container.

2. An apparatus as claimed in claim l, further including a mounting plate for mounting the submersible pump in close proximity to the sensor.

3. An apparatus as claimed in claim 1, further including a discharge outlet and means to place the discharge outlet in fluid communication with the outlet of the submersible pump.

4. An apparatus as claimed in claim 3, wherein the means to place the discharge outlet in fluid communication with the outlet of the submersible pump is a conduit.

5. An apparatus as claimed in claim 2, further including means to adjust the relative position of the sensor and the bottom of the container. - 17 -

6. An apparatus as claimed in claim 1, wherein said sensing means includes a pair of spaced-apart probes, and a circuit between the spaced-apart probes, said circuit capable of being completed by water to energize the alarm means.

7. An apparatus as claimed in claim 1, wherein said pump energizing means includes a power source and a switch in series between the power source and the pump such that closing the switch connects the pump and the power source to energize the pump to cause the pump to operate to take water into the intake and discharge it from the outlet thereof.

8. An apparatus as claimed in claim 6, wherein the alarm means includes at least one of an audible and visible alarm.

9. An apparatus as claimed in claim 8, further including test means for testing the integrity of the audible and visible alarm.

10. An apparatus as claimed in claim 6, wherein the probes are of substantially zinc having a layer of gold plated thereon.

11. An apparatus as claimed in claim 1, wherein said at least one container includes more than one and said alarm means is energized by a signal from one of said sensors.

SUBSTITUTE SHEET