Stop guessing. Enter your stock SH%, target application strength, batch size, and surface — get exact gallons, surfactant oz, and a safe dwell window instantly.
Do not let SH dry on surface — rinse before window closes.
Rinse Protocol
§5194 HazCom / 29 CFR 1910.1200: Mixing SH at 3%+ triggers OSHA HazCom requirements.
SDS must be on every truck. Crew must have documented PPE training before mixing.
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Use C1×V1 = C2×V2: SH gallons = (target% ÷ stock%) × total batch gallons. For 12.5% stock to a 1% mix in a 5-gallon batch: (1 ÷ 12.5) × 5 = 0.4 gallons SH. Fill the rest with water. This calculator does that math automatically for any stock strength, target, and batch size.
How long should SH dwell before rinsing?
Dwell time depends on substrate, growth type, and ambient temperature. Vinyl siding: 3–7 min at 1–2%. Roof shingles: 10–20 min at 1–3%. Concrete: 5–12 min. EIFS/Dryvit: 2–5 min at max 1%. This calculator applies surface, growth, and temperature modifiers to every estimate automatically.
What concentration is safe on EIFS or Dryvit?
Maximum 1% SH on EIFS. Above 1% blisters the acrylic finish coat — irreversible damage. Never use acid on EIFS. Pre-wet before application, use low-volume soft-wash only, and rinse with gentle pressure — no impact.
Does mixing SH at 3%+ trigger OSHA requirements?
Yes. Mixing sodium hypochlorite at 3%+ triggers OSHA HazCom (29 CFR 1910.1200) and Cal-OSHA §5194 requirements. You must have an SDS for every chemical on the truck, and crew must have documented PPE training before mixing. This calculator flags the requirement automatically.
How does ambient temperature affect dwell time?
At 90°F+ you lose 25–40% effective dwell time versus a 75°F baseline because SH evaporates faster. Apply in shade on hot days, shorten dwell toward the lower end. In cold temps below 50°F, SH reaction rate slows — extend toward the upper end. This calculator applies a temperature modifier to every estimate.