Water Reuse for Fun and Profit

There are a number of ways homeowners can reduce their water usage. Take shorter showers. Take fewer showers. Use water-wise drought tolerant landscaping. Those are ways that may come at some personal inconvenience. But there are other ways that have a small upfront cost but little or no inconveniences. Here I’ll share ways and ideas I’ve looked into for reducing water usage by reusing water.

Greywater laundry-to-landscape

15-45 gallons/load… maybe 2000 gallons/year

Last year I setup a greywater laundry-to-landscape system. It was a project that was fun to compete and has paid dividends. It’s been working well for the past year and the plants are thriving with it. It feeds 3 loquat trees, birds of paradise, and a strawberry patch. I get to admire it whenever I pass by and know that I’m reducing my water bill and not wasting water.

It took a bit over a weekend to install with more time waiting for parts to ship. The hardest part here was planning for all the equipment. There are plenty of websites that advise on planning and DIY systems (greywateraction), but the experience is rough and could be enough of a hurdle to turn off many folks with less time or will. I think there is opportunity for a company to provide a more modular plug-and-play solution here. This is also where your local water district can make the most difference. The Santa Clara Valley Water District, which provides San Jose and other neighboring counties with water, incentivizes greywater reuse with a rebate program. Overall the rebate nearly covered the cost of purchasing parts and install time. Highly recommend it.

Roof rainwater collection

2000 sq-ft house x 17 inches rain/year x 0.623 gallons/1 inch-sq-ft = 21,182 gallons/year

Over the last couple years I also setup a number of rain barrels. 6 at the moment. One for the shed, one for the ADU, and 4 for the house. They’re all connected to downspouts, and thus harvest rainwater that falls on the roof. Even without rain, the ADU one gradually fills up from collecting morning dew that collects off the roof. They all mostly serve as long term storage to provide water for gardening during the dry Summer months. With filtering, they could also serve as a backup water in case of an emergency that knocks out the water supply. Although there could be much larger concerns in that case. The barrels are all repurposed discards from various industrial uses — sugar syrup, liquid soap, fish sauce. The last one being the worst to clean up. They can be picked up off Craigslist from someone with a connection in those industries. Rinsing them out and installing the hardware is quick. Connecting to a downspout or linking barrels is also quick. I put a soaker hose on the last barrel in the chain so that the overflow will spread the water over a larger area. Overall much cheaper than store bought considering time and money, plus you’re giving the barrels a second life.

Automatically switching the rain barrel spigots to irrigate plants is a next step. Ideally it should hook into my Rain Machine system to irrigate based on the rainfall and rain forecasts.

Shower water reuse

3.5 gallons/min x 5 min/shower x 1 shower/2 days x 365 days/year = 3,193 gallons/year

Reusing shower or bath water is trickier to add into an existing system. Adding more piping and a valve switch to control landscape vs drainage is difficult and expensive to add on. Without that, the options are to keep the existing system, but plug the drain to collect water as you shower. That water can then be siphoned or pumped to the toilet or out a window to the yard. There’s even a siphoning tool just for this purpose called siphonaid. I tried this, but ultimately stopped as the inconveniences were too many. I didn’t enjoy water pooling by my feet. There is room for improvement here. Maybe a platform with reservoir to avoid the soggy feet issue.

Now I mainly focus on shorter and less frequent showers. And changed my frame of mind to consider that less time in the shower is more time for other rewarding activities.

Kitchen water reuse

3-10 gallons/load… maybe 1000 gallons/year

Reusing water from the kitchen is complicated as oils and salts from dishes may not always be suitable for the garden. Dishwasher and kitchen sink setups have similar problems as the shower. I’ve setup outdoor sinks with buckets under the drains. The bucket water goes to the garden. I imagine a similar setup could be done for the kitchen sink with a 3 way valve to switch between the sewage drain and the bucket. But moving the bucket around indoors is probably not worth the effort and spill risk. Another area for improvements.

Toilet water reuse

1-1.6 gallons/flush

Urine for a surprise. A couple options here. You can update the toilet tank basin to act as a sink. This is popular in Japan. The water gets used once to wash your hands, and again to fill the toilet tank which is used for flushing. There’s a product cleverly named Sink Twice which can do this for you. The downside is that it’s plastic and may not fit the tank perfectly. There is definitely room for better design here. I would much prefer a higher end ceramic one that fits the tank.

Another option is to forgo the bathroom and avoid flush water altogether. Pee in the garden directly, or use a purpose built watering can first. Urine can be used as a fertilizer. Anecdotally I tried this as an experiment with growing patches of corn one season. One patch got plain water, the other urine diluted with water. The corn with urine grew bigger. Rich Earth Institute is a great resource on this. You can take it further by making your own composing toilet. The “humanure” produced can be used in the garden like other manures.

Recycled water

Water reuse for drinking water requires high levels of filtration and UV sterilization to reduce contaminants and pathogens. Recycled water on the other hand requires less processing, is cheaper, and is suitable for plants. Every use case that doesn’t involve humans or animals could leverage recycled water. That includes landscaping, parks, golf courses, farm irrigation, industrial, and construction uses.

Overall there seems to be room to develop better systems for water reuse across the home especially for retrofitting.

One thought on “Water Reuse for Fun and Profit

  1. I had no idea each load of laundry was 40-45. Wow! This is a great resource. The equations are helpful for understanding the relative effects of each water diversion method. Thanks for aggregating all this info!


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