I have a three-tier fountain made of one 1/2, and two 1/3 cuts of wine barrels. I've tried pool paint, roofing paint/patch, pond liner, and finally settled on fiberglassing the barrels. It lasted 15 years, now I need to start over as the wood had started to rot and fall apart. Pond liner was very difficult to form and the thick wrinkles looked bad IMHO. Prefab liners wouldn't fit right...
It started to leak recently so I tried roofing patch, still leaks. I'm going to buy new barrels and fiberglass the like before and hope to get another 15 years.
The hand pump is removed from the top.
Good luck.