An average sized brick in my toilet tank would raise the height of the water 3/8 of an inch. Someone might have mentioned water height but it was not the reason for pushing bricks. Brick insertion did not require a plumber in most cases, that is why they chose that method. What I found astonishing was that I heard no one mention adjusting the float as an easy alternative. It would take instrumentation to measure the difference in flow with a 3/8" change in water height. A one quart jug would however raise my tank water level 7/16 of an inch, now your starting to talk big numbers, much better than a brick.