Minimum Isolation Distances

When you install your well, drainfield, and/or septic tank, you must observe minimum isolation distances as indicated in the table below. In some cases, isolation distances must be increased.

Note: If your property is hilly, the well should be located up hill from the drainfield or upstream from your drainfield site.

Item

Septic
Tank

Drainfield

Well**

Property Line

10 feet

10 feet

-

Building Foundation
(no basement)

5 feet

10 feet

3 feet

Basement Wall

10 feet

15 feet

3 feet

Water Supply Well*
(25 feet deep or more)

50 feet

100 feet

-

Lake or Stream

25 feet

50 feet

**



* Isolation distances will be increased for wells serving other than individual dwellings, and may be increased if wells are drawing water from an unprotected aquifer.

** A well cannot be located in an area subject to flooding.


For more information, please contact:

  • Your Area Sanitarian (based on your Township)
  • Washtenaw County Environmental Health Division - (734) 222-3800
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