ExteriorClean HQ

Soft wash mix ratio calculator

Enter your SH strength, the strength you want on the surface and your tank size; the calculator returns gallons of SH and water, the tank strength a downstream injector needs, and cost per batch. It is dilution arithmetic (C1 x V1 = C2 x V2), not a recipe - your product label governs.

Updated 2026-09-23 · 1 source · By the ExteriorClean HQ team

Soft wash mix calculator

Dilution math (C1 x V1 = C2 x V2) for sodium hypochlorite. Choose batch (mix in the tank at final strength) or downstream (injector pulls chemical into the water line at a set ratio). The target strength is yours to set - follow the product label and your surface.

Check the label - pool chlorine is commonly sold around 10-12.5%.
Measure your own injector - draw varies with tip size, hose length and machine.

Arithmetic only - not a recipe or efficacy claim. Sodium hypochlorite is corrosive: wear eye and skin protection, never mix with acids or ammonia, pre-wet and rinse plants, and follow the product label and Safety Data Sheet. Registered products must be used according to their label directions.

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How the calculator works

Batch: SH gallons = tank gallons x target % / starting %. Water = tank - SH.

Downstream: an injector drawing 1 part chemical to X parts water dilutes the chemical tank by (X + 1). So the chemical tank must be target % x (X + 1). If that exceeds your starting strength the target cannot be reached with that injector - the calculator shows 0 under “achievable” and caps the result at full-strength SH.

Worked example: 12.5% SH, 1% target, 50-gallon batch tank: 50 x 1 / 12.5 = 4 gallons of SH plus 46 gallons of water.

Safety

Sodium hypochlorite is corrosive. Wear eye and skin protection, never mix it with acids or ammonia-based products, pre-wet and rinse plants, and keep runoff out of storm drains where local rules prohibit it. Follow the product label and Safety Data Sheet (see NIOSH Pocket Guide).

Pressure washing contract + waiverCovers plants, runoff and pre-existing damage.

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Software for exterior cleaning operators

Pressure washing softwareQuotes, routes and invoices for washing crews (in development).Instant quotes from your price sheetMeasure, price and send before you leave the driveway.Window cleaning softwareBuilt around recurring rounds.Pricing: $39/mo founding rateOne published price, locked for founding members.

Frequently asked questions

What is the formula for a soft wash mix?

C1 x V1 = C2 x V2: SH gallons = tank gallons x target strength / starting strength.

How do I mix for a downstream injector?

Multiply your target strength by (injector ratio + 1) to get the strength needed in the chemical tank, then dilute your SH to that strength.

What percentage should I use for a house wash or roof?

That depends on the surface, the product label and local conditions - we do not publish recipes. Set your target and the calculator does the math.

Sources

  1. CDC/NIOSH Pocket Guide to Chemical Hazards (accessed 2026-09-23)
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