Starting a siphon in a over flow help needed

[Mihai]

My tank is drilled on the bottom for the overflow. This is for circulation (unfortunately it isn't drilled for circulation too. It's too late now to drill it (got DSB+LR+softies) now, so I'm wishing for the next best thing: an overflow with two inputs (any can fail), each with its own venturi and I'll try to get the pump to stop if the overflow stops (use one of those float switches). It will not be fool-proof, but close: you'll have to have three failures at the same time (both overflow pipes and the float switch) to burn the pump. In any case there will be no mess (when water stops overflowing will stay in the main tank).

M.

 

[gabemerrill]

I understand now, was thinking about the inital posts in this thread...

For a closed loop all you risk is frying a pump. But why use an overflow when you could just put the inlet for the pump in the overflow below the standpipe? This way no u-tube, siphon, or venturi... just a single pump and pvc. I may be missing something basic here but check out this diagram and tell me what you think...

 

[Mihai]

Well, if the power goes out, then comes back (something that happens at least once a week here) your pump will run dry. And burn.

Other than that, it's OK (maybe except the fact that it's hard to start it initially). Oh, and the fact that the pump will have to pull the water up (acting like a valve on the input -> not great for the pump's lifetime).

Finally, your overflow box must be able to handle both the flow to your sump and the flow of the closed loop. Depending on total flow, how many teeth you have and how low is the box you may be able to handle it or not...

M.