Chandler is a blended-water city. The utility mixes Central Arizona Project water sourced from the Colorado River with Salt River Project surface water and local groundwater, and the resulting hardness typically lands between 12 and 16 grains per gallon depending on the ZIP and the season. That is hard enough that whole-home softeners are common but far from universal. Homes without a softener deposit mineral scale into every unsealed grout joint every single time the floor is mopped, and the joint is porous enough to lock that scale in permanently.
Almost the entire Chandler housing stock built between 2000 and 2018 - most of Ocotillo, most of Sun Groves, big pieces of Cooper Commons and Clemente Ranch, all of the Kyrene 85226 corridor - was installed with unsealed sanded grout. Sanded grout is essentially a hard sponge: it wicks up water, food spills, pet accidents, and cleaning-product residue and holds them in the pores below the surface. A cotton-mop household cleaner cannot pull that residue back out.
Layer on Chandler's 300+ sunny days per year and monsoon season from July through September, and the fine desert dust that blows in each summer bonds to the mineral scale already sitting in the joint. By year three most Chandler homes have grout that looks two full shades darker than the day it was laid. Truck-mounted extraction with a high-heat rotary tool is the only reliable way to pull that soil back out - a mop and a bucket cannot.
For a deeper technical read, see our guide on why grout stays stained no matter how much you mop and our vinegar & DIY tile cleaner damage report.