There are many reasons we might be interested in ultra-low water use buildings.
To begin a list, we might live in an area which has low rainfall and limited water abundance. We may want to reduce expenses from high water use, wherever we live. We might seek to stop unsustainable draws on local groundwater, and thus perhaps ensure adequate spring and surface water for natural wildlife and the carbon-sequestering ecosystems around us. Or either practically or philosophically, we may wish to build off-grid in as many ways as possible, be free of centralized utilities and their bills, and live with a higher degree of natural autonomy, freedom, and resilience than is typical today.
Whatever our motivations for examining and pursuing this goal, let me say upfront that genuinely radical reductions in water use are normally possible in much of the industrially developed world, without significant reductions in our material quality of life. As we will discuss, thanks to modern technology, and in most areas – and almost always in ones with above 30 cm (12 inches) of annual rainfall – it is possible to live a fully modern life with on-site captured rain and other precipitation as our sole source of water.
Importantly, while our discussion will focus on residential or domestic water use, all of its its lessons are directly applicable to commercial and institutional buildings. On the other hand, water use in industrial manufacturing is clearly a separate and more ranging topic, with different issues and differing opportunities across various industrial sectors.
However, while we will only briefly touch on this area here, the case of both industrial and domestic food production is worth highlighting as part of our core discussion. Simply put, with careful water consumption, the use of modern permaculture techniques, and movement to more natural and naturally water-conserving perennial food systems (a topic I have summarized here), the above rule of deriving all needed water from on-site precipitation also broadly applies to agriculture as well.
Lastly for this introduction, our discussion notably will assume the presence of abundant low-cost electricity, a proposal that seems reasonable, across the developed world at least, in our era of increasingly low-cost solar collectors and batteries (a trend I have explored here).
WATER USE IN THE DEVELOPED WORLD
As you likely appreciate, we use a great deal of water throughout much of the developed world. Excluding water used in industry, agriculture, and outdoors, domestic water use is often in excess of 200 liters (~50 gallons) per person per day, or more than 73,000 liters (~19,000 gallons) per year.
If you will pardon a bit of math, these numbers come from combining the average household water use figures in the chart above, which are expressed in gallons, and then dividing this sum by current average US household size, which I have rounded to 2.5 people, given the only indicative nature of my calculations. More precise and geographically broader measures of water use are possible, but this rough estimate is more than adequate as a working proxy for indoor domestic water use in the developed world, as a frame for our discussion and given its focus.
This focus of course is our potential for ultra-low domestic water consumption, again amid otherwise affluent or recognizably modern life. More specifically, my aim is to show both that this outcome is plainly possible today, and both how and to the extent this is so. Taking this last point first, and assuming existing or soon-to-be-available technology, it appears that average domestic water use can be readily reduced by more than a factor of ten, dramatically curtailing water use and likely making 100% water autonomy – again via collected onsite precipitation and notably without the use of wells – a realistic goal for most single-family residences.
The calculations that lead me to these perhaps startling conclusions are summarized in the table below, with the technology allowing such reductions described in the next section of our discussion. Please note that the amounts shown below are in gallons, so that they track with the figures in the pie chart.
|Indoor Residential Per Person Daily Water Use (Gallons)|
As you can see in the table, and using the techniques and technology I will describe next, I have substantially lowered water usage across all of these core categories, and brought two of them to zero. Once again, these amounts do not include agricultural and outdoor water use, which similarly have the potential for site-level autonomy as well, and the figures again also do not account for water used in the provision of industrial products and services.
However, you will note that I have included water used for household vegetable (non-staple) gardening, since this is an opportunity to highlight the potential for low water use in this important, instructive, and transferable area. On the other hand, and perhaps to the dismay of some, the estimates assume no residential pools or even bathtubs in either the as-is or to-be projections, though each form of water use, while significant, may be possible on a sustainable or autonomous basis in some climates.
ULTRA-LOW WATER USE TECHNIQUES
Ultra-low water use is a change best pursued on many fronts. Much like low energy and resource-use more generally, reduced water usage begins with curiosity and a commitment to pursue options and alternatives at nearly every turn. That said, our largest typical areas of current water use should be understood as likely to yield the biggest impact, and the water conservation techniques we will discuss next are therefore roughly ordered from greatest to lowest average area of residential water use and thus opportunity for impact.
Importantly, this list of techniques once again assumes no significant alteration in lifestyle or modern activities of daily living. With the techniques, we still can clean ourselves, our clothes, and other possessions, and hygienically process our bodily wastes, in ways that are comparable to status quo conditions in the developed world today. Also, none of the techniques use practices or materials that are substantially more difficult, costly, or resource-intensive compared to ones in use today (though this is clearly an option for added water savings, and notably might include various dry cleaning methods).
> Toilet – as you can see in the chart and table above, flushing toilets are often the largest source of indoor domestic water use, and also where the largest impact in my prototype water reduction model occurs. As you might have guessed, this reduction is simply achieved by eliminating flushing toilets altogether and moving to waterless ones. On this point, let me underscore that there are a number of options for moving to dry and what are inevitably aerating or aerobic toilets – each with varying degrees of overall simplicity, ease of use, need for ductwork, and potential for odor. But again given my goal of minimal disruption to modern living patterns, my assessment is that the best zero-water toilet for most people in the developed world, at this time, is the Separatt toilet or an equivalent product, . In this overall approach, (normally sterile) urine is routed way from air-dried solid wastes and into sewer, septic, or compositing systems. This step greatly simplifies system operation in practice, reduces both needed ductwork and the potential for odor, and importantly allows a design that closely resembles traditional toilets.
> Daily shower – after flushing toilets, the second largest use of indoor residential water typically is showering. While reducing the frequency and duration of showers, or slowing water rates while lathering, are clear options for reducing water use, many modern people would find this an inconvenience and so these measures are not considered here (but might be used to reduce water consumption even further). Instead, my prototype system uses a recirculating shower, such as Orbital Systems or one of several similar products, where used shower water is diverted from drain pipes, filtered, reheated, and reused until the end of the shower session – in a closed loop that allows both extended hot showers and greatly reduced water use.
> Faucets – third on our list of indoor domestic water use sources is faucets, whether in kitchens, bathrooms, or utility areas. Today, a variety of low-flow faucets are available, which may reduce water usage in half or more, but unfortunately will not achieve our goal of a more than 10X reduction in water usage from faucets. To achieve this even lower level of water consumption, we instead will need to turn to misting or vaporizing faucet nozzles, such as Altered or an alternative product, all of which are just coming to market now and still subject to limited availability (though this is likely to change in the next year or two). Importantly, my water use targets in this area assume that most dishwashing will occur in higher efficiency automated dishwashers, for both water use optimization and in keeping with our goal of conforming to typical modern lifestyle practices where possible.
> Clothes – next in our survey of residential water use is clothes washing. Today, low-water washing machines are becoming the norm. These machines, like low-flow faucets, often can reduce water consumption roughly in half compared to earlier technology. However, the approach once again will not achieve the water reduction goals that are possible, and still newer clothes washing technology is needed. In principle, this will take the form of Xeros Technologies washers or equivalent products, which are now available for commercial use, but have not yet been downsized to a residential scale (or upgraded to provide integrated and space-saving drying). Using only a minimal amount of water and reused microbeads, this fairly new technology achieves remarkable water use reductions, while offering a familiar modern clothes washing experience. And while on the topic of clothing, I would be remiss if I did not add that we today all of the potential to quickly save significant water and energy by washing most of our garments less frequently than is the norm, and also choosing new clothing that requires less cleaning, needs shorter machine cleaning cycles, and uses less or little energy to dry after cleaning.
> Leaks – were you surprised to see system leakage as a frequent primary water use in modern homes? Whether in the more obvious form of leaking faucets, valves, and toilets, or more latently as water working its way out of plumbing joints and connections, and utility pipelines, residential water leakage in fact can be quite significant. In this area, my prototype water plan moves to reduce leakage to near zero, notably through regular assessments and prompt action when and where leaks are discovered. If this seems a significant and impracticable undertaking, I would ask you to consider this proposal in the context of an ultra-low water use and perhaps water-autonomous building, where the overall system is much smaller and simpler than is typical, where there are fewer opportunities for leakage, and where even small leaks would significantly impact water usage and quickly materialize on the building’s water meter.
> Dishwasher – in part because less water is needed for dishwashers relative to clothes washing machines, at least with traditional technology, and in part owing to recent advancements in dishwasher technology, achieving our goals for water reduction in dishwashing is fairly straightforward today. Currently, there are a number of dishwashers that use a very low volume of water and also often low energy amounts too (though in a clear theme in our discussion, there can be a natural tradeoff between using less water and less energy in dishwashing and many in other areas). Notably, my projections assume roughly one dishwasher cycle per week per person, and therefore that cookware and utensils used daily would be hand-washed in a misting kitchen sink faucet. In addition, while on this overall topic, let me also provocatively highlight our potential to dirty fewer dishes than is typical, and perhaps achieve significant personal health benefits, by eating fewer meals and less frequently.
> Other indoor – in addition to eliminating baths and pools from both the typical and target water use patterns in the table above, my prototype water use model assumes similar indoor water use reductions in all other areas. I won’t catalog particular water uses in this other category, since they may be highly variable and specific. But I will emphasize that the plan assumes that all such uses will be identified and prove fairly obvious, that steps can and will be taken to similarly reduce or eliminate water consumption in these areas, and that technological or other creative solutions will be possible in all cases.
> Vegetable garden – lastly, and as indicated earlier, I have included modest vegetable gardening in both my typical and target water use projections, since this is a potential, and potentially very healthy, form of domestic water use. Importantly, it is also a topic that allows us to end our discussion with an instructive study in possible water savings both outside our residences and in food production more generally. In particular, my projections assume a small outdoor growing area of about a square meter (~12 ft2) per person, and therefore one that requires about four liters or a gallon of water per day using traditional gardening methods, but that also can be designed to use much less water via alternative gardening practices. These include heavy soil mulching and minimizing soil disturbance, kitchen waste composting and regular soil amendment, underground drip or targeted watering in the early morning, selecting plants with comparable use and nutrition that require less water, and growing plants closely together in synergistic groups or guilds.
Overall, this brief but ranging discussion of ultra-low water use buildings likely has given you a lot to think about. As indicated at the start, there are a number of reasons why the goal of very low water use and site-level water autonomy, in residences and beyond, may be important to you, your family or organization, or larger community. But in nearly all cases, I think you can see that it is a realistic and economical goal, and potentially a highly beneficial one too.
I welcome your comments and questions on this crucial topic in modern natural design and development.
Mark Lundegren is the founder of ArchaNatura.
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