As interpreted by our plumber, some standard or other says that the sewer pipe has to be set in "quarter minus" (all the stones pass through a quarter inch sieve) screenings. This is good as a packing material that won't settle and bend the pipe later, but it does allow ground water to pass. We found that when it rained, the services trench full of quarter minus directed lots of water into the under-house space. The answer was the now named "Hoover Dam" which was commissioned on Sunday 11-07-04 and proved itself during the rain on Wednesday 14-07-04.