Visit the Chester County Health Department - keyword "sewage".

Below are the minimum isolation distances for Chester County.

Minimum Isolation Distances for Septic Tanks and Aerobic Tanks to:
Property Line, Easement, or Right-of-Way ...............................................10'
Occupied Buildings, Swimming Pool, and Driveways .............................10'
Individual Water Supply or Water Supply Suction Line ..........................50'
Water Supply Line Under Pressure ...........................................................10'
Streams, Lakes, or Other Surface Waters ..................................................25'
Cisterns used as a Water Supply ................................................................25'
Minimum Isolation Distances for Absorption Areas to:
Property Line, Easement, or Right-of-Way ...............................................10'
Occupied Buildings, Swimming Pools, and Driveways ............................10'
Individual Water Supply or Water Supply Suction Line â¦â¦â¦â¦â¦â¦.100'
Water Supply Line Under Pressure â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦10'
Streams, Lakes, or Other Surface Waters ..................................................50'
Other Active On-Lot Systems ................................................................... 5'
Surface Drainageways, Stormwater Basins, Rain Water Pits ...................10'
Mine Subsidence Areas, Mine Bore Holes, or Sink Holes â¦â¦â¦â¦â¦..100'
Rock Outcrop or Identified Shallow Pinnacle ...........................................10'
Natural or Manmade Slope Greater Than 25% .........................................10'
Cisterns used as a Water Supply.................................................................25'

Thank you so much!
I'm guessing she was mistaking the 100' Individual water supply for the septic