A couple of days ago I was washing dishes and the sink tended to fill up. Now I needed a pump to exert some pressure so the water could drain. I didn’t have one, so I figured I could pour in a lot of water altogether, causing there to be pressure and allow the rest of the water to drain away.
There was for me no other way to alleviate the situation, in the span of time that I had. I imagine God does the same with us. He sees a need in our lives, and the only way to clean us out for His purpose is through some pressure in our lives.
He could do it slowly, but in the interest of our mortal and therefore limited time, He’s got to use pressure.
Same way as when flashing the water closet. A little water at a time may work, but it could take forever to see any changes, to get any results. That’s why we need the pressure.