Interesting....
Not sure if you already mentioned it but will the tank be empty when you do the conversion?
Do you have any pictures of the configuration of piping to the sump?
Would it be possible to drill the top backside of the tank for a couple of bulkheads?
the piping could definitely be smaller for the full siphon... 1" does around 1500 l believe.
you would likely run into noise issues with the trickle pipes going around 90 degree elbows. they are normally silent because of small layer of water is stuck to the wall with the center of the pipe airspace, this would probably become turbulent at the elbow...
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