Field Pressure Testing (DW) Double-Wall Tanks: Procedures and Cautions
Field pressure testing of DW fiberglass tanks is an important verification step to confirm tank integrity prior to installation. These procedures are provided as a supplement to the Fiberglass Tank Solutions Installation Manual and Operating Guidelines (IMOG) and apply to all FTS double-wall tank configurations.
While pressure testing is not required when FTS tanks meet IMOG “As-Received” requirements, this procedure may be used when troubleshooting or verifying tank condition. FTS ships dry-monitored double-wall tanks with a factory-installed test manifold on the interstitial monitor fitting. Brine-monitored tanks require the contractor to supply testing equipment.
Testing equipment must include calibrated pressure gauges, pressure relief protection, and properly sealed fittings. During testing, the primary tank is pressurized first, followed by controlled pressure bleed to the interstice for dry-monitored tanks. Soap solution is applied to fittings, manways, and seams to visually confirm leak-free performance.
Pressure must be monitored for a minimum of one hour. Any pressure loss, gain, or visible bubbling indicates a potential leak and requires immediate coordination with FTS before installation.
Never overpressurize tanks or leave a pressurized tank unattended. Strict adherence to pressure limits, safety warnings, and IMOG guidelines is required at all times.
