Normally the head pressure of water is .433 pounds per foot of head. Is there any change in pressure by changing the tank water capacity. e.g. if two tanks of 50ft height having water capacity of one is 10,000 gallons and other one has 20,000 gallons. What will be the water pressure difference between two tanks.

No difference. The pressure changes with height of container, not width.

No difference. The pressure changes with height of container, not width.

If the 2 containers were linked at their bottoms by a pipe, surely the 20000L tank would empty into the 10000L (given there's enough capacity) until they were both 15000L.

My understanding is that the 20000L tank would have to exert larger pressure than the 10000L tank in the pipe to accomplish this...

if the 2 containers were linked at their bottoms by a pipe, surely the 20000L tank would empty into the 10000L (given there's enough capacity) until they were both 15000L.

my understanding is that the 20000L tank would have to exert larger pressure than the 10000L tank in the pipe to accomplish this...

The water will flow to it's lowest level, in other words it will minimize the potential energy of the system.

Potential energy depends on h only.

Normally the head pressure of water is .433 pounds per foot of head. Is there any change in pressure by changing the tank water capacity. e.g. if two tanks of 50ft height having water capacity of one is 10,000 gallons and other one has 20,000 gallons. What will be the water pressure difference between two tanks.

There would be no difference between the two. . 434 X a 50 foot head would give you 21.7PSI.

f the 2 containers were linked at their bottoms by a pipe, surely the 20000L tank would empty into the 10000L (given there's enough capacity) until they were both 15000L.
my understanding is that the 20000L tank would have to exert larger pressure than the 10000L tank in the pipe to accomplish this...
Sure loooks that way don't it? Common sense should tell you that with twice as weight the 20k tank should drain right into the 10K tank as soon as the pipes were connected. Right? WRONG!! Head pressure again! No matter how much volume you have inn the containers water will allways seek it's own level. Since the head remains at 50 feet both tanks will read out at 21.7 PSI. Regards, Tom

"Water pressure against tank height and tank water capacity" - Yes, the pressure in water, and of water, at a certain level depends on the height of water above this particular level only. But you can't say that the pressure created by water on the tank's walls depends on the capacity of the tank, because this is not always true. The pressure of the tank on the floor (or in other words, weight of the tank) depends on the capacity of the tank and also on the area of the bottom of the tank, which makes the contact with the floor.