How to make a constant flow rate of water from a tank with a faucet at the bottom side?

Question

Consider I have water tank as shown by the picture. By normal condition, the flow rate when the tank is full is higher than when the tank almost finish, and till it finally finish it will stop (in this case, what we consider is until the water level reaches the upper side of the faucet). But I want the water inside the tank flows from the faucet at constant flow rate without any additional electronic/microcontroller device. I want a pure mechanic, hopefully I may have a simple one. My question then, is any method to do it?

Answer 1

I didn't know the answer to your question so I searched for "constant flow water valve" and found plenty of results. Here's one:

Figure 1. When the pressure increases, the control rubber is pressed won into the conical seat and the orifice of the control rubber decreases. Image source: Berkfelt Teknik on YouTube.

Answer 2

Another type of 'constant flow' valve is a tornado valve, sometimes used to create stormwater overflow in sewerage systems. Incoming fluid at increasing pressure makes the tornado spin faster, and the held spinning volume provides back pressure, but the outflow is only from the free center -- where the height is only the height of the 'valve'.