How the soft wash mix calculator works
The amount of SH you need depends on how strong your SH is and how strong you want the mix. It's simple proportion: batch size × target strength ÷ SH strength.
Everything else in the tank is water. Surfactant is so small by volume that it doesn't change the math in a meaningful way.
SH loses strength with heat and time. If your jug has been sitting in a hot truck, test it and enter the real strength, not the label.
Tips from the trade
- Common starting points: about 1% for house washes and 3% to 4% for roofs. Always follow your chemical labels and test a small area first.
- Test your SH with a titration kit every week or two in summer. A weak jug is the most common reason a roof doesn't come clean.
- Wear eye protection and gloves, and never mix SH with acids or ammonia.
When you need more than a free soft wash mix calculator
This calculator answers one quick question. Running a business means doing it on every job, with your own rates saved and a quote you can send.
Soft wash mix calculator questions
What percentage should a soft wash mix be?
Many pros use about 1% for vinyl siding house washes and 3% to 4% for asphalt shingle roofs. Always follow your chemical labels and local rules, and test a small area first.
How do I mix 1% SH from 12.5%?
For a 50 gallon batch, use 4 gallons of 12.5% SH and 46 gallons of water. That's about 1 part SH to 11.5 parts water.
Why isn't my roof coming clean?
Weak SH is the usual cause. Pool shock and SH lose strength in heat. Test your jug and enter the real strength here.
Does this work for downstream injectors?
This calculator is for batch tanks. The full Soft Wash Chemical Mix Calculator also handles downstream injector ratios.