When the Deetzes are first moving into the Maitland's home, Charles says "We're going to have to rip out all that plumbing, but other than that it's perfect"- why would he see the need to "rip out the plumbing" in an otherwise "perfect" house?
Because it's old and noisy.
The line does not appear in the version of the script I found but there is a more informative wording that would appear to explain it.
CHARLES The noise in that kitchen. Noisy refrigerator, noisy faucets... We'll have to replace it all. I want no humming in the house.