B737-200ADV Hydro Sys
 

I was looking at Boeing 737-200adv hydraulic system and one thing is bothering me.
I see that all three hydro systems A,B and stand by are interconnected by fluid balance lines
which got me to one question that i hope is easily answerable but i can not see it.

Lets say that you have a fluid leak somewhere in the system A. Does this mean that if you fly for a longer time lets say 1h – 2h – 15min you could be facing full loss of hydraulic fluids?
I guess that Mr. Boeing has done something to prevent this situation i just don’t see it.
Any help from experts on this beautiful old bird is much appreciated.

Thank you very much

That is exactly what can happen. Experienced that situation a few years ago. A passenger later told me he saw fluid leaking right after take off but he didn't tell anybody as he thought it was only fuel...

Than this is really bad!? Is it possible that they haven’t thought of that? For what do i have stand by system when they are all non restrictedly interconnected.
There must be something thisplane is flying for decades now.

Here it´s, what you are looking for
 

The three are in different levels, the system A is above all and the sys B is behind it, the stand by system is at the bottom. If you go to the whell well aera you will see clearly the connections between them, and then you will realise the thing you have imagined, Mr. Boeing has imagened too, many year ago.