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Glad i went with a test run in basement! I setup a used sump setup with my 55 tank. It has an overflow box and u tube, 3/4 hose to fill sump and 5/8 tube return with pump. Last night everything was working perfect, i even went downstairs a half dozen times to check. This morning i went to check on it, and only about 2 gallons left in main tank !!! Could not have been overflow box right? could i have had a reverse siphon from the return hose?

has to be a leaking 55 gallon tank

i have had a reverse siphon from the return hose?

unless the return hose was on the bottom of the 55 gallon tank
give me a call

Since i was just in test mode, yes! i did have the hose just stuck in the tank near the bottom. I figure if i use a spray bar this wont happen ??

Correct.
he water will only be able to drain as low as the spray bar is on the tank.
It's a good idea to drill a small hole in the return elbow going into to the tank to be able to break the syphon if your power fails.
Also, make sure you do not have your sump completely filled. you need room to allow water to fill in case of a power outage.