Concrete Tank Leak Test

[Will007]

Hi,

Does anyone know what the allowable leakage is for a concrete tank. Some say its 0.5%. Is this correct?

We just put a 150k gallon up and is ready for commision, but we need to verify that the leak test passed.

Please advise.

Thanks

 

[Ussuri]

The text below is copied from the British Standard for water retaining tanks. Probably not applicable for you but might give you some idea.

When first filled, the liquid level should be maintained by the addition of further liquid for a stabilizing period while absorption and autogenous healing take place. The stabilizing period may be 7 days for a maximum design crack width of 0.1 mm or 21 days for 0.2 mm or greater. After the stabilizing period the level of the liquid surface should be recorded at 24 h intervals for a test period of 7 days. During this 7-day test period the total permissible drop in level, after allowing for evaporation and rainfall, should not exceed 1/500th of the average water depth of the full tank, 10 mm or another specified amount.

 

[JedClampett]

We use .1% per day.

 

[bimr]

A. Upon completion, the tank shall be tested to determine watertightness. The tank shall be filled with potable water to the maximum level.

The test shall consist of measuring the liquid level over the next 24 hours to determine if any change has occurred. If a change is observed and exceeds the maximum allowance, the test shall be extended to a total of five days. If at the end of five days the average daily change has not exceeded the maximum allowance, the test shall be considered satisfactory.

B. The liquid volume loss for a period of 24 hours shall not exceed one-twentieth of one percent of the tank capacity, 0.0005 x tank volume. If the liquid volume
loss exceeds this amount, it shall be considered excessive, and the tank shall be repaired and retested.

C. Damp spots will not be permitted at any location on the tank wall. Damp spots are defined as spots where moisture can be picked up on a dry hand. All such areas shall be repaired as necessary.

D. Damp spots or standing water on the footing may occur upon tank filling and are permissible within the allowable volume loss. Measurable flow in this area is not permissible and must be corrected.

 

[RWF7437]

"10 mm or another specified amount."


Perfect !

 

[Ussuri]

RWF7437, yeah, that is a good one. I believe the purpose of the statement is to allow you to impose a more restrictive limit if you so desire.

 

[JStephen]

If it's built to an AWWA standard, that standard should specify allowable leakage.

 

[cvg]

A properly constructed concrete tank should exhibit essentially no leakage. If any leaks are observed on the structure or on the ground, they should be investigated and repaired. Go with the smallest allowable amount you can measure. This will depend a bit on the geometry of your tank and your measuring equipment. BIMR's spec is probably about the smallest amount you can easily measure. However, now that the tank is completely constructed is a bit late to tell the contractor what the allowable leakage will be.