The Denver City Council has given the green light to using “graywater” to save freshwater.
Denver Sustainability Strategist Sonrisa Lucero says graywater from bathroom and laundry room sinks, bathtubs, showers and washing machines can be used to irrigate landscaping and to flush toilets.
Use of wastewater from toilets, urinals, kitchen sinks or non-laundry utility sinks is prohibited, she said.
It’s important to conserve freshwater, she said, “because Denver is growing in population but our water resources aren’t growing. We have to find other ways to reduce consumption.”
Lucero said there are two types of graywater systems approved for residential and commercial use.
“Laundry to Landscape is a passive system,” she said. “You use the pump on your washing machine to put water out onto your landscape.”
Avery Ellis, of Colorado Greywater, told Denver7 that the Laundry to Landscape system simply requires a valve and some pipes to bring washing machine water out of the house and into a mulch basin in the yard.
“The system does have an upfront cost,” he said, “but it’s mitigated because you are no longer using freshwater to irrigate your landscape.”
He estimated that a simple Laundry to Landscape system would cost from $200 to $1,000 for the average homeowner.
The other system, which would be used to capture graywater to flush toilets, is a little more complex.
It would require a special valve, storage tank, extra pipes and a separate pump.
The city said estimates for that type of system range from $1300 to $2800 for the average home.
Ellis said he can envision large scale versions of that system being used in new hotels and dorms.
“Imagine if an entire hotel was capturing all the shower water from the hotel and using it to pump to their toilets, so they’re no longer using fresh, clean drinking water in their toilets,” he said.
Lucero told Denver7 that if graywater is going to be used to flush toilets, or if it’s going to be stored for irrigation, “there will be some treatment required.”
She said that treatment may involve either a filter or chlorine.
Lucero also said there will be a requirement to put dye in the graywater.
“You want to make sure that you know it’s a non-potable,” she said, “so when the water is sitting in the toilet bowl, you’re actually going to see a different color. Not that anyone is going to drink it, but we all have pets and kids and that can be a challenge to make sure we keep water safe for them at all times.”
Lucero also said people shouldn’t confuse graywater with “recycled” water, which is treated wastewater that is pumped back into the city from the wastewater treatment plant, via purple pipes, and then sprayed onto grass and trees at several golf courses and parks.
“That water is treated to 1980 standards,” she said. “Graywater is not.”
Ellis, who helped define the new graywater law, said he’s grateful that Denver is now onboard.
"It's going to save water," he said.
Lucero said final regulations allowing graywater systems in Denver still have to be formulated and approved by the Denver Board of Health. She said that's likely to happen this summer.
The sustainability expert said the Graywater Program will give the Mile High City another opportunity to conserve water and to achieve the 2020 sustainability goal of reducing water consumption by 22 percent.
“No one wants to go looking for new water resources, or to build new dams,” she said. “It’s best to live within the resources we have. This is a great opportunity for us to do that.”