When should the standard threaded plug be installed in STI-P3 tanks?

The standard threaded plug should be installed in STI-P3 tanks prior to testing for a critical reason. Installing the plug at this stage ensures that the tank is sealed properly, preventing any leaks or contamination while the tank undergoes necessary tests, such as pressure testing or leak testing. This step is vital for verifying the integrity of the tank and ensuring that it is safe for use.

If the plug were installed at any stage after testing, it could compromise the test results, as any leaks that may exist would not be detected. Similarly, installing it before filling the tank could lead to situations where the tank is untested and therefore potentially unsafe for holding fuel or other hazardous materials. Thus, the sequence of installing the plug before conducting any tests is essential for maintaining the tank's compliance and safety standards.