(1) Primary underground piping connected to above ground tanks or to underground tanks with a capacity of 660 gallons or less used exclusively to store heating oil for consumptive use on the premises where stored may be constructed of copper provided that the piping is enclosed in secondary containment consistent with these rules.

(2) In addition to cathodically protected steel or non-metallic pipe listed for use with petroleum products and/or motor fuels, schedule 40 or greater PVC pipe and fittings may be used to provide secondary containment for heating oil tank systems subject to this rule provided that only adhesives resistant to petroleum products are used to bond PVC joints.

(3) If liquid or vapor sensors are not used to monitor the interstitial space for a release, the piping system must be installed so that any liquid released into the interstitial space will not move more than 20 feet before being visually detected in a sump or standpipe.