Issue Date:  August 23, 1999
Revision Date:  June 27, 2011

Containment Solutions, Inc. 
(originally listed as Fluid Containment and O/C Tanks)

FCI Liquid Filled Interstitial Monitor
Tank Model DWT6 with Model FHRB 810 Level Sensor


Certified as a continuous, liquid-filled interstitial space, leak detection system for all size tanks manufactured by Containment Solutions, Inc., at time of evaluation.

Operating Principle:
A fluid reservoir is attached to the top of the tank and is open to the interstice through the bottom. The interstice is normally filled with a brine solution in freeze areas or water in non-freeze areas. The fluid reservoir is equipped with a dual-point level sensor to provide for low level and high level alarms. The dual-point level sensor system monitors the liquid level in the interstitial reservoir and provides an alarm if the liquid level is either too high (ingress of liquid) or too low (egress of liquid).


Containment Solutions, Inc. underground double-walled piping as specified above containing gasoline, gasohol, diesel, heating oil #2, kerosene, aviation fuel, or motor oil.

Test Results:
System is capable of detecting leaks of 0.1 gph or smaller within one month for all size tanks manufactured by Containment Solutions, Inc., at time of evaluation.  
Estimated time to activate alarm, given a leak rate of 0.1 gph and assuming initial reservoir is 2 inches below full, ranges from 4 hours for a 500 gallon tank to 267 hours for a 50,000 gallon tank.  
Minimum detectable leak for alarm within one month ranges from 0.0047gph for a 500 gallon tank to 0.0185 gph for a 50,000 gallon tank, if initial reservoir level is 50%.  
Other test results listed below.

Summary of Variable Ranges Measured in the Evaluation

  Evaluation variable

Range of conditions

Estimated range of effect for gasoline on brine level (in)

Product level change in tank

From 0% to 90%


Water table changes

48 inches change


Temperature changes

From 40 to 100 degrees F.


Vapor trapped in interstice (with temperature change)

45 gallons air trapped
(with temperature change from 40 to 100 degrees F.)


Manufacturer’s Specifications:
Fluid in reservoir must be filled to proper level.
When alarm condition exists, or annually, sensor must be removed and tested in a bucket of water, according to manufacturer's instructions.

Evaluation conducted on DWT6 20,000 gallon tank with a R28 reservoir and FHRB 810 sensor.   Other sensors can be used only if they are a dual-point, will properly fit into the reservoir, are compatible with the interstitial liquid, and are on the NWGLDE list.
Evaluation parameters included:  tank product level changes, water table changes, temperature changes, measurement of trapped vapor in the interstice, leak effects on the liquid-filled interstice, and scaling factors (application to various tank sizes).
System was not evaluated for ability to detect layer of hydrocarbon on water.


Containment Solutions, Inc.

Evaluator:  Ken Wilcox Associates

5150 Jefferson Chemical

Tel:  (816) 443-2494

Conroe, TX 77301-6834

Date of Evaluation:  06/15/98

Tel:  (800) 628-2657



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