jvc66 this is what inwas talking about.
1st pic showes the water level with the pump running (black line)
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This is what the pumps off and the water back flowed through the return pipe. Would be much higher and flood the sump if not for the siphon break drilled at the return line in the tank.
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Now with thise two lines i know the level to refill the sump when the system is off (during water change) of toping it off while the system is on.
When its off i fill to the blue line knowing that any higher i am at risk for flooding.
While its running and i just want to top it off (adding more water) i fill to the black line knowing if i fill any higher i am again at risk for flooding when i turn the system off.
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You just have to play around with it once you set everything up.
These marks are from when i first set it up. Testing various levels until inwas comfortable with the off and running level.
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You could use tape instead of a marker...i dodnt care what it looked like inder the hood lol. Sump is 30 gal and display tank is 150 so not allot of room for error
Is your return just pvc pipe that you drilled the siphon break in? I was thinking of using one of those flexible spray nozzles attached to a bulkhead so how would that work without a break