Potable Rainwater Collection + Greywater Garden Irrigation Systems
NexusHaus captures rainwater to supply the majority of its potable water needs, relying on a city water refill line only for backup during long dry spells. The potable rainwater harvesting system minimizes added stress to the region’s water supplies, and minimizes the additional load on the existing neighborhood water and wastewater infrastructure. Additionally, the on-site treatment system avoids water losses along the municipal distribution system (which are typically average approximately 10%). The thermal storage tank acts as a secondary storage volume for rainwater, giving the system additional capacity while also providing beneficial load shifting.
Figure 1 shows the rainwater harvesting system portion of the ITHERST system for NexusHaus. Rainwater is collected off the roof and pre-screened for large debris, and the first-flush diverter redirects the initial rainfall away from the rest of the rainwater collection system. An additional inlet may be used to screen for organic matter (such as leaves, bugs, etc.) from the incoming water to minimize contaminants accumulating in the primary collection tank. The primary rainwater collection tank catches rainwater, and stores it for eventual consumption in the potable water system, or transfers it to the rainwater thermal storage tank, provided it is not full and/or occupied by thermal storage operation.
When potable water is needed in the house, rainwater is pumped from the primary storage tank through a filtration and treatment system. A pressure tank helps maintain system pressure and keeps the rainwater pump from short cycling. The filtration and treatment system filter and treat water to potable water standards, and then feed into a domestic water system, distributing hot and cold water to each of the end uses.
Water supplied to the kitchen sink, the dishwasher, and the toilets will be collected and conveyed to a blackwater tank (or the sewer). These sources of wastewater typically contain high levels of organic matter (and/or other pollutants), which make it unsafe to reuse without treatment. However, water supplied to the bathroom sink, the shower, and the clothes washer will be collected and conveyed to a greywater system for beneficial re-use outside of the house.
The greywater collection tank accumulates greywater and periodically pumps it into a subsurface irrigation system. The garden maximizes the utility of this precious water source by featuring a landscape designed for food production and water filtration as part of a sustainable garden ecosystem. < The rainwater thermal storage tank is used for the indirect water thermal storage with the hydronic cooling and heating system during the summer months when thermal storage operation is desired over additional rainwater system capacity. In the non-summer months, the rainwater thermal storage tank acts as additional capacity for the rainwater harvesting system.