A few calls over to Mr. Rooter later and it seems as though they’re ready to start doing a bit of their own research into water conservation techniques. So far, I don’t have much for them to go on — they’ve found some water recovery systems, although nothing geared towards small residential buildings. Researching this stuff has been slow going for the most part, many of the sites out there focus on conservation (turning off the water while brushing your teeth, reducing shower duration etc..), so it seemed like a good idea to write into the NYC DEP commissioner to find out what’s available and go from there. More on that when I get a reply. Other steps I’ve seen, while somewhat costly, could eventually recoup the cost of installation:

Tankless Point of Use Water Heaters 
Tankless Water Heater design means that water is heated instantly, but only for as long as the hot water is being used. Conventional tank water heaters, on the other hand, heat water 24 hours a day, 365 days a year – and guess who pays for the energy it takes to keep the water hot… (source)

Bosch AquaStar (250SX) – pricing on amazon.com
Among other benefits, this is also covered by the Energy Policy Act of 2005. (bosch link, WikiPedia link)

GREY WATER: The term refers to domestic wastewater from kitchen sinks and tubs, clothes washers, etc. It can be reused for gardens and lawn watering.
Grey water heat recovery 

XERISCAPE: This water-saving approach to landscaping incorporates design, soil analysis, plant selection, maintenance, mulching and other practices. More than 40 states have xeriscape projects.

Related links and inspiration

Sustainable House
Home Energy Online
Home Power Magazine
Harvest H20.com