Soft Wash vs Pressure Wash Chemical Dilution Calculator

Calculate the exact amount of chemical concentrate and water needed for soft wash (low-pressure, high-chemical) and pressure wash (high-pressure, low-chemical) applications. Enter your tank volume, desired concentration, and chemical stock strength to get precise mixing instructions.

Common Settings

Example: Standard sodium hypochlorite (bleach) pool shock = 12.5%, household bleach = 3–8%

Soft Wash Settings

Typical soft wash range: 0.5% – 3% for roofs, siding, and organic stain removal Optional. Typical surfactant rate: 0.25% – 1% of total mix volume

Pressure Wash Settings

Typical pressure wash downstream injection range: 0.05% – 0.5% Most downstream injectors dilute at 10:1 to 20:1. Leave blank if not using injector.

Formulas Used

Dilution Formula (C₁V₁ = C₂V₂):

  • Volume of Concentrate = (Target Concentration % ÷ Stock Strength %) × Total Volume
  • Volume of Water = Total Volume − Volume of Concentrate − Volume of Surfactant
  • Dilution Ratio = Stock Strength % ÷ Target Concentration %

Downstream Injector Formula:

  • Required Tank Concentration = Target Surface Concentration × (Injector Ratio + 1)
  • Example: To get 0.5% at surface with a 10:1 injector → Tank must be 0.5% × (10 + 1) = 5.5%

Surfactant Volume = (Surfactant % ÷ 100) × Total Volume

Assumptions & References

  • All concentrations are expressed as percent active ingredient by volume.
  • Standard sodium hypochlorite (SH) pool shock is typically 12.5% active chlorine; household bleach ranges from 3% to 8.25%.
  • Soft wash applications typically use 0.5%–3% SH for organic stain removal (algae, mold, mildew) on roofs and siding (PWNA guidelines).
  • Pressure wash downstream chemical injection typically dilutes at 10:1 to 20:1 (water:chemical) depending on injector orifice size.
  • Surfactant (soap/degreaser) is typically added at 0.25%–1% of total mix volume to improve dwell time and surface adhesion.
  • 1 US gallon = 128 fluid ounces = 3.78541 liters.
  • Formula reference: C₁V₁ = C₂V₂ (standard dilution equation, general chemistry).
  • Always follow chemical manufacturer SDS (Safety Data Sheet) guidelines for safe handling, PPE, and disposal.
  • Do not mix sodium hypochlorite with acids, ammonia, or other incompatible chemicals.
  • Results assume ideal mixing with no chemical degradation or evaporation losses.

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