Free Tool
Soft Wash Dilution Calculator
Mix the right batch every time. Enter your tank, your SH strength, and the percent you want - get exact gallons of bleach, water, and surfactant.
A soft wash mix is just sodium hypochlorite (SH) diluted down to the percent that kills organic growth without damaging the surface - usually around 1% for a house wash and 2–3% for a roof. The math is simple but easy to get wrong on a busy morning: the gallons of SH you need equal your batch size times your target percent divided by the percent strength you bought.
This calculator does it for you. Enter your tank size, the SH strength on the jug (pool-supply SH is usually 10–12.5%), and the strength you want on the surface, and it returns the exact gallons of SH and water - plus your surfactant. Always add SH to water, wear eye and skin protection, and pre-wet plants before and after.
Frequently asked questions
- What percent should a house wash mix be?
- Most house washes land around 0.75–1.5% SH on the surface, adjusted for how heavy the growth is. Light, regularly cleaned siding needs less; heavy mildew needs more dwell time, not necessarily a stronger mix. Roofs typically run higher, around 2–3%.
- How do I calculate a soft wash dilution ratio?
- Gallons of SH = batch size × (target % ÷ SH % you bought). For example, to hit 1% in a 50-gallon tank from 12.5% SH: 50 × (1 ÷ 12.5) = 4 gallons of SH, with the rest water plus surfactant. This calculator does that math instantly.
- Can I make a 3% mix from 6% bleach?
- Yes - 6% hardware-store bleach can reach low percentages, but you use far more of it and it is weaker and pricier per gallon than 12.5% pool SH. If your target is close to your SH strength, you have little room for water. The calculator warns you when a target is higher than your SH can reach.
- How much surfactant do I add?
- A common starting point is 1–3 oz of surfactant per gallon of finished mix to help the solution cling and dwell. Follow your surfactant maker’s label; this tool multiplies your per-gallon amount by the batch size so you get the total to pour in.
Keep the math with the work
WashRoute Pro keeps your owner-entered assumptions with quotes and scheduled work so you can review the price, customer contact, and schedule before anything goes out.
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