FishinGal,
I used 4" sewer and drain PVC and when the lift hit 10' the tubing collapsed for 10' on top of the dam. The corrugated stuff is a lot weaker it is designed to handle some pressure but NO vacuum and will most likely collapse at the 6'-7' lift height. Try some PVC on top of the dam with a Tee at the highest point. You an use electrical tape to secure and seal the corrugated tube on the outlet side. Get a rubber cap for the Tee and a test plug to stop up the inlet and outlet. Then you can fill the whole tube from the Tee and cap the Tee when full. then FIRST pull the plug under the water THEN unplug the outlet and WaLaa you drain until the inlet sucks air. Once the pipe is full you can also check for any leaks and seal them with the electrical tape. Not as hard as it seems and will cost about 80-$100.