Data visualization is hard, particularly the d3.js library. It takes time, patience, skill, and luck.
If I had more time, skills, and patience with programming, there are some things I would want to add to this project.
First, I would add demographic data for each borough. My focus on the housing characteristics data is limited without more information on the people who live within the Census tracts. Second, I would add some data that might indicate vulnerabilities around clusters of inadequate plumbing. Namely, a layer of FDNY fire stations, a layer of density of 311 calls regarding heat and hot water complaints, and a layer of other water sources available (such as public bathrooms and pools). I might also add a layer of data regarding 311 calls for homeless persons "in need of assistance".