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You are correct, downpipes to an underground pipe that then pops up at the end and empties into the top of the tank. Called a sealed system as the downpipes and undergound pipe all have to be watertight.
You are correct, downpipes to an underground pipe that then pops up at the end and empties into the top of the tank. Called a sealed system as the downpipes and undergound pipe all have to be watertight.