California Plumbing Code Section 407 governs residential bathroom fixture clearances. Water closet: 15 in min from centerline to any side wall, 24 in min clear in front (CRC R307.1 allows 21 in for residential). Lavatory: 4 in clear on each side. Shower: 30 in by 30 in min interior dim, 1024 sq-in min floor area, 24 in clear at entry. Venting per CPC 905: each fixture trap arm max horizontal distance from vent (typ 5 ft for 1.5 in, 6 ft for 2 in trap). Reno gotcha: relocating a toilet over 3 ft requires re-running the vent, often the most expensive part of a bath remodel.