I drained a 1 acre pond with 4 inch pvc pipe and flex connectors this past spring. A few lessons I learned:
Put a screen over the inlet pipe in the lake to avoid muck and stuff from being pulled in.
I attached a float (duck decoy) about two feet above inlet so it floated out when first setup.
Attach more pipe on inlet when you installsince you have to start over if you need more.
When filling pipe, I used buckets first time and an electric sump pump the second time.
When using flex connectors, wrap each connector with duct tape, a lot, to ensure vacuum is not broken at a coupler. I learned this after trying to get it restarted about 10 times. Fish hatchery guy said wrap each joint that is on vacuum side.
After pipe was filled, I found unscrewing the cap a difficult job. On my last setup, I just loosened the flex connector with a screw gun. A lot easier.
You won�t get all the water out, very hard to seine fish with mucky shores.
4 inch pvc drained lake much quicker than I thought, about 6 days, 12 feet of water, estimated flow rate of >200 GPM.

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