In the case where a sanitary sewer or water district shall include areas wherein sanitary sewers or water systems have been constructed under the authority of the county government, or by municipalities, corporations or individuals, the necessary adjustments shall be made with each property owner for those costs already incurred by the property owner when those sewers or water systems were constructed. Such excess costs shall be credited to future assessments levied by the district.

9 Del. C. 1953, § ?6510; 55 Del. Laws, c. 262; 57 Del. Laws, c. 762, § ?8A;