question about brakes

[hongo]

My 02 Sedona's brakes failed last week due to badly leak in a rear brake line. The brakes have been fixed by replacing the broken brake line. However I still have a question about the brakes failure: on modern cars the brake system is supposed to have two separated circuits, in case of one of the circuits leaking the other one should not be affected so the car can still stop with brakes on the two unaffected wheels. However in my case, although only one rear brake line leaked and all other brake hydraulic systems were fine, I totally lost all of the brakes at the time, when I pressed the brake pedal it went all the way down to the floor and gave no brake at all. I asked the Pepboy's mechanic about it, he told me once a brake line leaks the whole hydraulic system will lose its pressure thus all brakes would be lost. This explanation is different from what I learned from articles about modern cars' brake systems, such as this one: Howstuffworks "How Master Cylinders and Combination Valves Work". Does this mean Sedona does not have two separated brake hydraulic circuits? I think this may be against the law if it is true.

[Classic boy]

It does have a dual system, it is a legal requirement on all cars.
The pedal does drop a long way if one of the 2 systems does fail but it should still work on the remaining system. If it didn't the master cylinder may need attention.