This is getting complicated. Ive done this manyl times. Just get a. gas gransfer pump on the end and suck water through the pipe. When water starts fliwing out remove the pump hose and the siphon will do the rest. 5 minutes and done. You just need to prime the line which is also very easy.

Ive drained 2 ponds this way and dozens of pools. If you dont have a fransfer pump they rent them for super cheap at home depo or lowes or other rental companies.

easy peasy.