Persistent water source.

As i put the water on stairs (like a villager house roof) from below, the water source remains even after i take it back or i cover it. 

What I expected to happen was...:
The water source should have disappeared.

What actually happened was...:
As i put the water on stairs  (like a villager house roof) from below, the water source remains even after i take it back or i cover it. The only way i succeed to remove the source was to destroy the block.

Steps to Reproduce:
1. I put the water source on the roof (bucket with water) to use it as an elevator.
2. When i removed the source from the roof (wooden stairs) the water source persisted even after being covered.
3. Only when the block was destroyed, the source was gone.