There are two posts located inside the pop bumper area of a White Water pinball. Stretched across these posts is a rubber (see photo to the right) creating a "shield". This "shield" cuts off a small lane for the ball to travel, stops the ball from entering / exiting the pop bumpers from this location, and prevents the ball from hitting the two switches directly below it (granted.....they only give 10-points a hit....but as Martijn van Aken once said on the pinball newsgroup......"they make a cool sound").
The general consensus on the newsgroup was that they installed it after the "test" games showed a large amount of right drains. The ball would bump around for a while, exit through that particular lane, and head straight down the right side. Therefore, the "shield" was created to solve the problem, forcing the ball to shoot out between the top and bottom bumpers.
However, many collectors have found that the removal of this post/rubber combo adds a little more action to the pop bumper area. It also allows the 10-point switches to be hit on a regular basis. This fact is beneficial because those two switches often cause a credit-dot on the display for not often being activated.
I removed the "shield" and have not noticed any more right drains than before. I did move the outlane post a little further inward just to be safe. However, most of the time the ball flies out toward the left side or down the right inlane straight to the flipper. I have also noticed what other collectors have: a little more and somewhat unique bumper ball action.
Below are some pics of my post removal with things apart and together. Click on an image to enlarge and for more info.
Remember, your milage may vary. Try it both ways and see which you like the best.
"It's a boulder bash!!! Yow. Yehaw!!! Yipee!!!"