Water Quality Improvement Act of 2017 This bill amends the Federal Water Pollution Control Act (commonly known as the Clean Water Act) by requiring the Environmental Protection Agency (EPA) to establish an integrated planning and permitting process for municipal wastewater and stormwater management that: enables municipalities to identify the most cost-effective and protective approaches to comply with the Act's requirements; helps them prioritize their investments in addressing the requirements; and is comprehensive and flexible. The EPA must provide technical assistance to the municipalities or states for developing an integrated plan upon request. The EPA must: (1) update its financial capability assessment guidance entitled, "Combined Sewer Overflows--Guidance for Financial Capability Assessment and Schedule Development," and dated February 1997; and (2) ensure that the guidance may be used for assessing the financial capability of municipalities to implement effluent limitations and other pollution control measures. During the next 5 years, the EPA must work with at least 15 municipalities to develop and implement integrated plans and permits to meet the requirements of the national pollutant discharge elimination system.