BERKELEY, Calif. — Showering during California’s drought is a guilt-free experience for homeowners Catarina Negrin and Noah Friedman.

The Berkeley couple — she runs a preschool, he’s an architect — are early adopters of a home plumbing do-over that’s becoming more popular during California’s record four-year dry stretch.

California, like many states, long required all water used in homes to be piped out with the sewage, fearing health risks if water recycling is done clumsily.

Since 2010, however, the increasingly dry state has come around, and now even encourages the reuse of so-called gray water, which typically includes the gently-used runoff from bathroom sinks, showers, bathtubs and washing machines.

As mandatory conservation kicked in statewide this month, forcing many of California’s 38 million people to face giving up on greenery, these recycling systems have become attractive options in new homes, right along with granite countertops. California Building Industry Association executive Robert Raymer rattles off the drought-conscious top builders that now routinely offer in-home water recycling.

And California’s building codes are catching up as well, allowing owners of existing homes to create the simplest systems for the safest gray water without a permit.

So while others think about hauling buckets to catch stray drips from their sinks and tubs, Negrin and Friedman can relax: Each gallon they use in the shower means another for the butterflies that duck and bob over their vegetable garden, for the lemon tree shading the yard, and for two strutting backyard chickens busily investigating it all.