Floating Water with No Blocks

Steps to Reproduce:

1. Make 5 dispensers around a block (like in FirstStep.jpeg).

2. Fill them with TNT.

3. Place a button in the middle of the blocks, and then water in the middle of the blocks (like in LastStep.jpeg)

4. Click the button.

Expected Result:

The water should flow down.

Actual Result:

The water does not flow at all. (like in Result.jpeg)