Acid Wash Pool Cost Calculator

Interior area. Footprint is length × width (round: π·r²). Wetted area adds the walls — perimeter × average depth — for the true plaster surface, which is roughly double the footprint. Average depth is (shallow + deep) ÷ 2. Oval and freeform pools apply a 0.85 bounding-box factor (an approximation, not a cited constant).

floor      = length × width            (round: π·(D/2)²)
avg_depth  = (shallow + deep) / 2
walls      = 2 × (length + width) × avg_depth   (round: π·D·avg_depth)
footprint  = floor
wetted     = floor + walls
refill_gal = footprint × avg_depth × 7.48        (when not entered)

billed_hours = max(labor_hours, 2)               2-hour minimum
labor_cost   = billed_hours × labor_rate
water_cost   = (refill_gal / 1000) × water_sewer_rate
base_cost    = labor_cost + acid + water_cost + supplies
subtotal     = base_cost × severity_mult         light 1.0 / mod 1.25 / heavy 1.5
price        = subtotal × (1 + markup_pct / 100)
implied/sqft = price / footprint                  always footprint, never wetted

The per-sq-ft cross-check always divides by footprint area (never wetted), so it stays consistent with the published $0.50–$0.75 per sq ft band — consolidated from HomeGnome ($0.60–$0.70), Homewyse ($0.56–$0.68), and FloridaDetail ($0.55–$0.67). A flag of "above" or "below" just means your own cost stack lands outside the national average — your real costs may justify it.

The job covered is the standard scope: drain → prep → apply diluted acid → rinse → refill. The 2-hour labor minimum and the $80/hr labor, $22 acid, and $114 supplies defaults come from HomeGnome's and Homewyse's decompositions; all are editable — regional spread is large (NYC ~$0.85 vs Dothan, AL ~$0.52 per sq ft), so no single rate is baked in.