There are more than 7,000 sheltered and unsheltered homeless people living in San Francisco. But there are less than two dozen showers available for them to use throughout the city.

Doniece Sandoval saw this lack of reliable hygiene services for the homeless and decided to act. Inspired in part by mobile food trucks, she founded Lava Mae (a play on the Spanish word for “wash me”), a mobile showering service that officially took to the streets last week.

Lava Mae operates out of a retired 1993 Muni bus, donated to Sandoval by the San Francisco Municipal Transportation Agency (SFMTA). It’s retrofitted with two shower suites each containing a shower, toilet, sink, and hair dryer — simple amenities often taken for granted. KQED reports:

In October, soon after she launched a fundraising campaign to raise the $75,000 needed to retrofit the first Muni bus, Sandoval challenged herself to go a week without a shower. “You’re supposed to think about these publicity stunts to raise visibility, but it was also a chance for me to kind of step in, in a very small way, to the shoes of the people that we would be serving.”

A self-described “clean freak,” Sandoval said she was already feeling “unsettled” by Day Two. When Day Seven arrived and she was able to take a shower, she cried.

According to Lava Mae’s website, the grey water produced by the showers is treated with an eco-friendly disinfectant and then drained back into sidewalk catch basins. Black water from the toilets is picked up by a wastewater hauling company. Though Sandoval might instal solar panels on future retrofitted buses, current models are equipped with rechargeable batteries inside the bus. Built-in skylights provide ample natural light.

Since Sandoval first announced plans for Lava Mae, people from more than 50 cities worldwide have reached out to her about implementing similar mobile shower programs. She also hopes to continue fundraising this fall to retrofit another bus. By replacing its oldest diesel buses with hybrids, the SFMTA hopes to become 100 percent emission-free by 2020; turning those old buses into showers for the needy instead of junking them outright strikes us as genius.