Chart · 3 minute read
Soft wash mix ratio: how much SH or bleach
Soft wash strength is a percent solution: the SH strength you have, the strength you want, and the size of the batch. Here is the math and a chart for the common strengths.
The formula
Soft washing is a percent solution problem. You know the strength of your sodium hypochlorite (SH), usually 10% to 12.5% pool chlorine or about 6% household bleach, and the strength you want on the surface.
SH needed = (target % ÷ SH %) × finished gallons
(1 ÷ 12.5) × 5 = 0.4 gal of SH (51 fl oz), plus 4.6 gal of water and surfactant.
Soft wash mix chart (5 gallon batch)
| Target strength | 12.5% SH | Water + surfactant | 6% bleach, per gallon |
|---|---|---|---|
| 0.5% | 0.2 gal (25.6 fl oz) | 4.8 gal | 10.67 fl oz per gal |
| 1% | 0.4 gal (51.2 fl oz) | 4.6 gal | 21.33 fl oz per gal |
| 1.5% | 0.6 gal (76.8 fl oz) | 4.4 gal | 32 fl oz per gal |
| 2% | 0.8 gal (102.4 fl oz) | 4.2 gal | 42.67 fl oz per gal |
| 3% | 1.2 gal (153.6 fl oz) | 3.8 gal | 64 fl oz per gal |
| 4% | 1.6 gal (204.8 fl oz) | 3.4 gal | 85.33 fl oz per gal |
Fresh SH loses strength with heat and age, so a jug sold as 12.5% may be closer to 10% by summer. Test strips or a titration kit tell you what you actually have.
Use % solution mode for any SH strength or tank size →Mixing safely
- Never mix SH with acids or ammonia (some cleaners and rust removers). It releases toxic gas.
- Wear eye protection and chemical gloves. Pre-wet plants and rinse them after.
- Follow the surfactant's own label for its rate.
Frequently asked
How much bleach for a 1% soft wash mix?
With 12.5% sodium hypochlorite, use 0.08 gallons (about 10 fl oz) per finished gallon, or 0.4 gallons in a 5 gallon batch. With 6% household bleach, use about 21 fl oz per finished gallon.
What is the soft wash mix ratio for roofs?
Roof mixes are usually stronger than house washes, often 3% to 4% finished strength, but follow your surfactant maker's guidance and the roofing manufacturer's limits.
How do I calculate a soft wash mix?
Divide the target percent by your SH percent and multiply by the finished gallons. 2% from 12.5% SH in 5 gallons is 2 ÷ 12.5 × 5 = 0.8 gallons of SH.
More: How to calculate spray mix rates · Backpack sprayer mix chart · Soft wash mix ratio · oz per 1,000 sq ft to oz per gallon
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