Have you ever really taken a close look at the interstice space of a double wall flex pipe? It’s real tiny isn’t it? Did you ever wonder how long it takes for product to travel thru that interstice space? I did. So I inquired. My research found as an example that the interstice volume is only 0.00246 Vol/Ft on one manufactures flex line. If the run of pipe is 100’, the total interstice volume is 0.246. The information that I obtained, indicates that the amount of time that it takes for product to move that distance based on a typical 1/8 inch pitch per foot would be 1.29 hours.

So you have this scenario; There is 100’ of DW flex piping buried from the tank pad to the dispenser islands. The piping is properly pitched at 1/8 minimum per foot. You have a sensor in the STP sump back at the tank pad. There is no sensor in the dispenser pan. You are relying on the sensor in the STP sump to notify you in the event of a leak because….. you have DW piping with interstitial monitoring. You still with me? The meter under one of your dispensers just blew a gasket and is now leaking. It’s dripping out of that meter at 2 GPH. But, under line pressure, this gasket blows out and the line is pumping at 27psi. Your mechanical leak detector in the STP sump doesn’t catch this. It only triggers at a catastrophic 3 GPH. But you’re a high pumping station, its noon time and the STP motor is constantly running due to the high demand. There is always one nozzle out of the cradle keeping that STP relay closed sending power to the STP. The mechanical leak detector didn’t even get a chance to run the 3 GPH test. How long do you think it would take to fill a typical 95 gallon dispenser pan at 27psi pumping at approximately 8.5 GPM? How about 11 minutes before it starts flowing out onto the island, over the pad, down the driveway, into the street, into a storm drain and into the local river. Liquid takes the path of least resistance. The product didn’t have enough time to make it from the dispenser pan to the STP sensor to trigger an alarm. Not in the 1.29 hours it would take for the product to start dripping into the STP sump. But, you tell me you have a fast thinking attendant monitoring your service station. He immediately hits the emergency stop button. This interrupted the power to the dispensers and will shut down the handle switch signal pulling in the STP relay. Phew! Major crisis averted, still a clean-up needs to occur - But wait, the relay is stuck closed. The power is still going to the STP – product is still flowing. HELP!

Your worst nightmare just came true. What do you do? Well for starters, before this scenario or something like it happens to you, install dispenser pan sensors under your dispensers. There is already a requirement from some states for continuous monitoring of the dispenser pan for product loss on new and substantially upgraded systems. And by continuous monitoring the intent of these regulations is to have a dispenser pan sensor located under the dispenser. Connecting the dispenser sump to a monitored tank top sump just doesn’t cut it. If you had a sensor in the dispenser pan, it would have triggered an alarm notifying you of an issue. The site attendant would then have time to investigate before the worst occurred.

You might want to also put into place a weekly visual check of the dispenser interior. This means opening the dispenser skirt and checking the components and piping. This way you may be able to identify any potential future issues, like weeping fittings or leaking meters and filters.  You can then be proactive on resolving any problems before they occur.

Third party management with remote monitoring of the automatic tank gauging systems is just one of ECS Eclipse’s specialties. We can take the headaches away. Please call for more information.

-Lorenzo DiBacco, Field Services Manager