Concrete Tank Leak Test
Concrete Tank Leak Test
(OP)
I have a concrete tank that needs a leak test done. The leak test will be done after its already been backfilled and the tank is 21m by 21m and holds about 3000m3 of water. Wall thickness ranges from 600mm at the bottom to 450mm at the top (7.1m tall). My question is once the tank is filled up, the concrete will absorb some of the water. How long should I wait before I start my actual measurement of change in water height. How long should I give the concrete to absorb the bulk of what it will absorb?





RE: Concrete Tank Leak Test
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.
Per AWWA, the allowable leakage rate is 0.1 percent of the water volume in 24 hour.
You can always specify higher requirements than the minimum standards.
This issue was previously discussed:
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RE: Concrete Tank Leak Test
Would you be able to provide me a link to this specification and also does the AWWA allowable leaked rate of 0.1 include concrete absorption? Shouldn't concrete absorption vary for different concrete mixes and other factors?
RE: Concrete Tank Leak Test
RE: Concrete Tank Leak Test
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You also have to allow for evaporation and rain.
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RE: Concrete Tank Leak Test
@jqeng: Please note that there is maximum rate of a filling for a water tank that is being filled for the first time. I have the uniform rate of not greater than 2 m in 24 h in back of my head.
Getting to your questions, the stabilizing period depends on the maximum design crack width and the time needed for the healing. I remember it was 7 days for a crack width of 0.1 mm according to BS. there is also a limit for the maximum drop in level during this 7-day test based on the full tank depth. I suggest to take a look to the latest BS standard. BTW, there is also a separate test for the roof.
RE: Concrete Tank Leak Test
@waterpipe: thanks for your response, as a note Im new and I didnt think that my first post worked so I reposted when I found this thread! Turns out they both worked.
RE: Concrete Tank Leak Test
RE: Concrete Tank Leak Test
I worked on a project where inadequate concrete consolidation resulted in significant segregration (you could see through the walls after the forms were removed. The contractor used epoxy grout repairs and tried testing with this method to check repairs.
Wave action was an issue to record surface level changes. We tried a stilling well but still could not get a "steady" level.
We excavated a few areas and found leaks where water squirted out of pinhole leaks. Additional repairs were required.
Depending on the purpose of the tank and future maintenance costs - you might consider coating the tank.
RE: Concrete Tank Leak Test
I was thinking of ordinary reinforced concrete water tanks (normally rectangular), which is not by AWWA. But I see no reason to apply the acceptance of the leakage for a prestressed concrete water tanks to the ordinary one.
RE: Concrete Tank Leak Test
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RE: Concrete Tank Leak Test
Sorry but I meant:
" I see no reason NOT to apply the acceptance of the leakage for a prestressed concrete water tanks to the ordinary one."
but I've missed the NOT, for the same reason I've missed "covered" before "by AWWA" in my respond! So I fully agree with you on applicability of the leakage rate.
Well, this could be the Friday afternoon "allergy", which means I have to leave the office for a happy hour! I do it in 10 minutes.
Have a nice weekend.