Wall-Wash Test Precautions and some Causes of Failure

• Always use disposable plastic gloves when wall washing – the human hand contains more salt than normal requirements and is a common cause of chloride contamination.
• Wear clean clothes and do not allow working gloves in the tank, avoid all contact of clothing with the tank, wear protective disposable shoe covers.
• Use a clean bucket on a clean line for transferring test equipment into the tank.
• Wash the funnel and sample bottles with certified methanol prior to collecting the sample.
• Always test the distilled water and certified methanol prior to use for testing and always run a standard against the test sample.
• The glue used for the seals on some types of sample bottles have been known to cause sample contamination.
• When using acids for washing wear the proper protective equipment.
• Take your time, sampling in a hurry or rushing through the test procedures cause failure.
• If the sample passes all tests, be suspicious, and test again.
• Never test a wet tank, the tank wall must be dry.
• Allowing a tank to “rest” after prolonged washing (especially hot washing) can often turn a failed tank into a passed tank.
• Keep a record of your wallwash results, especially if testing multiple tanks.  Consulting this record over days of tank cleaning may provide a useful indication of which washing procedure is working best.