A contractor is testing the potable water piping for a new residential installation. According to code, the system must be tested with water at a minimum of 100 psi for at least 15 minutes. What exception applies to this testing method?

• Except when testing with air, which is not permitted for plastic piping.
• Except when the static pressure is below 80 psi.
• Except when the piping is exposed in a crawl space.
• Except for systems serving only two fixtures.