Method and apparatus for monitoring an underdrain of a filter system

1. A filter system for filtering a liquid, comprising:

(a) a filter bed having at least one layer of filter media for removing impurities from a liquid passing through said filter bed;

(b) an underdrain operably associated with said filter bed for directing a fluid through said filter bed during a washing cycle to remove impurities retained in said filter bed during a filtration cycle;

(c) a first sensor for sensing at least one diagnostic condition relating to flow of the fluid through said underdrain; and,

(d) a controller for evaluating the at least one reading of said first sensor to determine whether the flow of fluid through said underdrain is within a predetermined acceptable level.

2. A filter system as recited in claim 1 , further including:

(a) an inlet conduit for directing influent downwardly through said filter bed during filtration.

3. A filter system as recited in claim 1 , further including:

(a) a washing pipe line for directing a washing liquid to said underdrain, said first sensor is a pressure sensor disposed in said washing pipe line upstream of said underdrain relative to a direction of flow of the washing liquid.

4. A filter system as recited in claim 3 , further including:

(a) a second sensor disposed downstream of said underdrain relative to direction of flow of the washing fluid.

5. A filter system as recited in claim 3 , wherein:

(a) said second sensor is disposed below a top surface of said filter bed and above bottom surface of said underdrain.

6. A filter system as recited in 4 , further including:

(a) a controller for evaluating at least one reading of said first sensor and at least one reading of said second sensor to determine whether the flow of fluid through said underdrain is being obstructed.

7. A filter system for filtering a liquid, comprising:

(a) a filter bed having at least one layer of filter media for removing impurities from a liquid passing through said filter bed;

(b) an underdrain operably associated with said filter bed for directing a washing fluid through said filter bed during a washing cycle to remove impurities retained in said filter bed during a filtration cycle; and,

(c) a monitoring means for monitoring said underdrain to determine whether said underdrain is performing at a predetermined acceptable level.

8. A filter system as recited in 7 , wherein:

(a) said monitoring means includes a pressure gauge for measuring pressure of a washing fluid, said pressure gauge being disposed upstream of a top surface of said underdrain relative to a direction of flow of the washing fluid.

9. A filter system as recited in claim 8 , wherein:

(a) said monitoring means further includes a pressure sensor disposed below a top surface of said filter bed and above a bottom surface of said underdrain, said pressure sensor being vertically spaced from said pressure gauge.

10. A filter system as recited in claim 9 , wherein:

(a) said monitoring means further includes a controller operably associated with said pressure gauge and said pressure sensor for receiving and evaluating pressure readings from said pressure gauge and said pressure sensor to determine if said underdrain is performing acceptably.

11. A filter system as recited in claim 10 , wherein:

(a) said monitoring means includes at least one of a visual alarm and an audible alarm for indicating to an operator that said underdrain is obstructed.

12. A filter system for filtering a liquid, comprising:

(a) a filter bed having at least one layer of filter media for removing impurities from a liquid passing through said filter bed;

(b) an underdrain operably associated with said filter bed for directing a fluid through said filter bed; and,

(c) a pressure gauge for measuring pressure of the fluid, said pressure gauge being disposed upstream of a top surface of said underdrain relative to a direction of flow of a washing fluid.

13. A filter system for filtering a liquid, comprising:

(a) a filter bed having at least one layer of filter media for retaining impurities in a liquid to be filtered;

(b) an underdrain operably associated with said filter bed for directing a fluid through said filter bed; and,

(c) a monitoring unit for monitoring differential pressure across two vertically spaced points of said underdrain to determine whether said underdrain is performing acceptably.

14. A filter system as recited in claim 12 , further including:

(a) a pressure sensor disposed below a top surface of said filter bed and above a bottom surface of said underdrain, said pressure sensor being vertically spaced from said pressure gauge.

15. A filter system as recited in claim 14 , wherein:

(a) a controller operably associated with said pressure gauge and said pressure sensor for receiving and evaluating pressure readings from said pressure gauge and said pressure sensor to determine if said underdrain is performing acceptably.

16. A filter system as recited in claim 15 , further including:

(a) at least one of a visual alarm and an audible alarm for indicating to an operator that said underdrain is obstructed.

17. A filter system as set forth in claim 13 , wherein:

(a) said monitoring unit is configured to obtain at least one pressure reading relating to flow of fluid through said underdrain, said monitoring unit is further configured to determine flow rate of a fluid when said at least one pressure reading is obtained.

18. A filter system as set forth in claim 17 , wherein:

(a) said monitoring unit is configured to determine whether said underdrain is performing at a predetermined acceptable level based at least in part on at least one pressure reading obtained.

19. A filter system as set forth in claim 17 , wherein:

(a) said monitoring unit is configured to determine whether said underdrain is performing at a predetermined acceptable level based at least in part on at least one pressure reading obtained and the flow rate determined.

20. A filter system as recited in claim 19 , further including:

(a) at least one of a visual alarm and an audible alarm for indicating to an operator that said underdrain is obstructed.