Mariposa County, CA Swimming Pools & Spas: Hot Tub Rules (2026)

Mariposa County's swimming pool handout is titled for both pools and spas, and the County applies the same permit and safety framework to hot tubs and spas. Unless a unit fits the narrow prefabricated exemption (less than 18 inches deep, no more than 5,000 gallons, entirely above ground, accessory to a single-family home) under 2025 CBC §105.2, a spa or hot tub installation requires a building permit. The submittal must document a drowning-prevention safety device or barrier approved under California Health & Safety Code sections 115920-115929 (at least two of seven approved features) and a GFCI-protected electrical system; heated spas also require Title 24 energy-compliance documentation. The required documents mirror those for pools: a spa information sheet, cover sheet/site plan, equipment plan, gas line diagram (if applicable), and structural calculations. One of the seven recognized drowning-prevention features is an ASTM F1346-compliant safety cover, which is commonly used for spas. Because the whole county is unincorporated, the County Building Department (209-966-3934) and Environmental Health (209-966-2220) administer these rules everywhere. Most permanently installed/plumbed spas will require a permit; owners should confirm with the Building Department before installation.