Try this: Get a sump pump and attach a garden hose to it. Put it in the tank and put the output on your lawn. Then turn on and drain your tank #1.
With the Python, vacuum tank #2 until you're satisfied its clean. Then when the tank 1 is drained enough move the pump over to tank 2 that you just gravel vacuumed and drain that one. Now you can gravel vacuum the first tank. When that's done just leave the python in and refill the water. This has saved me a lot of time and water plus my plants and lawn get all of the drained water from my tanks. It's like youre draining two tanks at once this way because your either gravel vacuuming or using a pump to drain each tank at the same time. Plus draining with a pump doesn't require using extra water and it's a lot faster than draining with a python.
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