SH Mix Calculator: Bleach-to-Water Ratios by Surface
SH Mix Calculator: Bleach-to-Water Ratios for House, Roof, and Concrete Washing
Enter the strength your bleach actually tests at, the mix you want on the surface, and the batch size. You'll get gallons of SH, gallons of water, the ratio, and surfactant ounces. Built by Sun Brite Supply for the contractors who buy our chemicals.
Bleach plus acid (muriatic, oxalic, phosphoric, citric, most rust and mineral removers, many concrete etchers) releases poisonous chlorine gas. Separate tanks, separate injectors, separate buckets. Rinse the surface and your equipment completely before switching from one to the other.
- Water to SH ratio7.3 : 1
- Surfactant total70 oz (0.55 gal)
- Finished batch50 gal at 1.5%
- SH jugs to bring (1 gal)6
Mix water first, then add SH, then surfactant. Use the batch the same day.
Formula: gallons of SH = batch size ร target % รท your SH %. Water is the rest. In downstream and X-Jet modes the calculator solves for what belongs in the bucket so the draw ratio lands your target on the wall.
Buy the chemicals this page assumes
Mix strength by surface
These are working ranges, not rules. Start at the low end, let it dwell, and step up only if the surface tells you to. Stronger isn't faster on siding or wood. It just strips more and damages more.
| Surface | Mix on surface | Dwell | Watch for |
|---|---|---|---|
| Vinyl and aluminum siding | 1 to 2% | 8 to 12 min | Rinse before it dries or you'll streak it |
| Painted wood and stucco | 0.75 to 1.5% | 5 to 10 min | Test a hidden spot. Paint reacts differently |
| Asphalt shingle roof | 2 to 3% | Until growth turns white | Zero pressure. Granules come off in one pass |
| Concrete and pavers | 3 to 5% | 10 to 15 min | Removes organic growth, not oil. Use Concrete Cleaner for oil |
| Heavy north-side growth | 5 to 6% | 15 min | Two light coats beat one hot one |
| Wood fences and decks | 0.5 to 1% | 5 min | Too strong greys the wood. Follow with Wood Britener |
Your 12.5% probably isn't 12.5%
Sodium hypochlorite breaks down on its own, and heat drives it. Decomposition roughly doubles for every 18ยฐF rise in temperature. A drum sitting at 95ยฐF loses strength around 14 times faster than the same drum at 59ยฐF. That's the gap between a shaded shop and a truck bed in July.
| What weakens it | What happens | What to do |
|---|---|---|
| Heat | Strength drops fastest above 85ยฐF | Never leave it in the truck overnight in summer |
| Sunlight | UV speeds decomposition | Opaque containers, stored in shade |
| Metal contact | Copper, nickel, and cobalt traces speed breakdown | No metal funnels, fittings, or drums |
| Low pH | Stable above pH 11. Falls apart fast below 10.8 | Never mix with anything acidic |
| Age | Stronger solutions decay faster than weak ones | Buy fresh 12.5% more often instead of stockpiling |
Test before you mix. Chlorine test strips rated to 15% get you close for a few dollars. A titration kit is more accurate and still cheap. Ask us for the fill date on your SH. A jug filled last week and one filled two months ago are different products at the same price.
Batch mixing or downstreaming
The calculator's default mode gives you the mix in the tank. If you spray that tank straight onto the wall, that number is what lands on the surface.
If you downstream, the injector dilutes it again. Most injectors pull somewhere between 10:1 and 20:1 depending on hose length, GPM, and how worn the injector is. That's why downstreamers usually pull straight 12.5% and let the injector do the diluting. Switch the calculator to Downstream, enter your draw ratio, and it tells you what to put in the bucket to land your target on the surface.
Match the injector to the machine
Draw depends on three things you control: the machine's GPM, the injector orifice, and how much hose sits between the injector and the gun. The calculator's Downstream mode uses all three to estimate your draw ratio. A bucket test still beats the estimate.
| Orifice | Machine GPM | Typical draw | Notes |
|---|---|---|---|
| 1.8 mm | 2 to 3 | 10:1 to 20:1 | Small residential units |
| 2.1 mm | 3 to 5 | 10:1 to 20:1 | Most 4 GPM belt-drive rigs |
| 2.3 mm | 4 to 6 | 10:1 to 20:1 | 5.5 GPM machines |
| 2.5 mm | 5 to 8 | 10:1 to 20:1 | 8 GPM machines |
| 3.0 mm | 8 to 10 | 10:1 to 20:1 | Large commercial units |
High-draw injectors pull close to 10:1, standard injectors close to 20:1. Every 50 ft of hose past 100 ft adds backpressure and weakens draw by roughly a point and a half. Past 300 ft most injectors quit. Move the injector downstream of the reel and closer to the gun if you run long hose. Shop injectors by orifice size.
Find your real draw ratio in two minutes. Put the injector line in a bucket with exactly 1 gallon of water. Run the pump with a soap nozzle for 60 seconds into a second bucket. Measure what's left in the first bucket and what landed in the second. Divide output by chemical drawn. If your injector pulls under 1 quart a minute on a 4 GPM machine, it's likely worn. Replace it here.
X-Jet and M5 X-Jet mix ratios
An X-Jet pulls chemical at the nozzle instead of at the pump, so the mix never touches your pump, hose, or gun and you can run a much hotter mix than a downstream injector allows. With no proportioner in the barb, a 4 GPM machine draws about 1.6:1 water to chemical. That means a bucket of straight 12.5% lands near 4.8% on the wall, which is too hot for siding. Most house washers either cut the bucket with water or drop in a proportioner. The M5 adds pattern control from pinstream to 60 degrees. The proportioners and the chart are the same for both.
Switch the calculator to X-Jet / M5, pick your machine GPM, orifice, and proportioner color, and it tells you what to put in the bucket to hit your target on the surface. Proportioner ratios climb fast with GPM, so a color that works on a 4 GPM machine is a different mix on an 8.
| Proportioner | 2 GPM | 3 GPM | 4 GPM | 5 GPM | 6 GPM | 8 GPM |
|---|---|---|---|---|---|---|
| None (open barb) | 0.8:1 | 1.2:1 | 1.6:1 | 2:1 | 2.4:1 | 3:1 |
| Grey | 1.4:1 | 2:1 | 2.5:1 | 3:1 | 4:1 | 4.9:1 |
| Black | 3:1 | 4:1 | 5:1 | 6.5:1 | 8:1 | 11:1 |
| Beige | 6:1 | 8:1 | 10:1 | 13:1 | 16:1 | 20:1 |
| Red | 9:1 | 12:1 | 16:1 | 20:1 | 24:1 | 28:1 |
| White | 16:1 | 22:1 | 30:1 | 38:1 | 45:1 | 51:1 |
| Blue | 20:1 | 27:1 | 37:1 | 46:1 | 55:1 | 61:1 |
Water to chemical, from the X-Jet proportioner chart. Beige and red are the usual picks for straight 12.5% SH or undiluted house wash. The calculator carries the full chart through pink. Ratios are approximate and shift with pump brand and elevation, so bucket-test when the number matters.
Size the orifice to the machine. #7 for 1 to 2.8 GPM, #9 for 3 to 3.5, #13 for 4 to 4.5, #16 for 5 to 6.5, #20 for 7 to 8, #25 for 8.5 and up. Wrong orifice means weak draw and a bad pattern. Keep X-Jets off asphalt roofs. Even at the widest fan the pressure is more than shingles want. Shop X-Jets and proportioner packs.
Surfactant and dwell do the real work
Surfactant doesn't make the mix stronger. It makes it cling long enough to work instead of sheeting off in twenty seconds, and it cuts surface tension so the mix gets into texture instead of sitting on top. Too little and it runs. Too much and you're paying for foam and rinsing longer for nothing.
| Product | Rate per 5 gal of mix | Best for | Shelf life once mixed with SH |
|---|---|---|---|
| Roof and House Wash | 6 to 8 oz | Roofs, siding, heavy growth. Bleach-stable, holds SH strength in the tank | Same day |
| Powerhouse | 1/2 gallon | House washing and exterior building cleaning where gutters, grease, and mixed dirt are part of the job | Same day. Do not save it |
Both work with sodium hypochlorite. The rule that matters is simple: use what you mix. A batch with surfactant in it is a same-day product. Mix it Friday and it won't perform Monday, whichever soap is in the tank. Pick the batch size above to match the job in front of you, not the drum you'd like to fill.
Dwell time matters more than concentration, right up until the mix dries on the wall. Keep the surface wet, work in shade when you can, and rinse before the sun does it for you.
Six ways to ruin a good mix
- Mixing off the label. Test your strength and enter the real number.
- Letting it dry. Streaks from dried SH don't rinse out later.
- Metal anything. No metal funnels, drums, or transfer fittings.
- Mixing with acid. Never. Sodium hypochlorite plus any acid-based cleaner releases poisonous chlorine gas. Separate tanks, separate injectors, full rinse between products. This is the one that sends people to the ER.
- Saving the batch. Mixed SH with surfactant is a same-day product. Tomorrow it's weaker and you'll blame the chemical.
- Going stronger instead of slower. Two light passes with dwell beat one hot mix, cost less, and don't burn the shrubs.
Protect the landscaping. Pre-wet plants and turf, keep them wet during the wash, then rinse and treat with Bleach Arrest. SH keeps working after the rinse, and that's when it burns leaves.
Questions contractors ask us
How much SH do I need for a house wash?
A typical single-story house takes 30 to 60 gallons of finished mix at 1 to 2%. At 1.5% from fresh 12.5% SH, that's about 4 to 7 gallons of bleach. Run your batch size through the calculator above.
Can I use this calculator if I downstream?
Yes. Switch to Downstream mode and enter your injector's draw ratio. It solves for what goes in the bucket so your target strength lands on the surface.
What ratio does an X-Jet pull with no proportioner?
About 1.6:1 water to chemical on a 4 GPM machine, 2:1 on a 5, 3:1 on an 8. Straight 12.5% in the bucket lands near 4.8% on the wall at 4 GPM. Add a proportioner or cut the bucket with water to get down to house wash strength. The X-Jet / M5 mode in the calculator does the math.
What percentage should I use on an asphalt shingle roof?
2 to 3% on the surface, applied at low pressure, and left until the growth turns white. Never use pressure. The granules are the roof's protection.
How do I find out my real bleach strength?
Chlorine test strips rated to at least 15% work for a few dollars. A titration kit is more accurate. Or buy fresh stock from us and ask for the fill date.
How long does mixed solution last in the tank?
Use it the same day. Diluted SH loses strength faster than concentrate, and once surfactant is in the tank the clock runs faster. A batch mixed Friday is noticeably weaker Monday.
Why did my mix work in April and stop working in August?
Your bleach degrades faster in summer heat, and the growth you're removing is at its strongest. Same recipe, weaker product, harder job. Test and adjust instead of blaming the chemical.
Does the calculator work in liters?
The math is the same in any unit. Enter liters in the batch field and the SH and water figures come back in liters. Surfactant is still shown in ounces per 5 gallons.
Do you ship sodium hypochlorite?
No. 12.5% SH is local pickup only at our Gaithersburg, Maryland warehouse. Surfactants, neutralizers, and most other chemicals ship.
Before you mix the next batch
Test what you have, enter it above, and mix to a number instead of a habit. It takes a minute and it's the difference between a repeatable result and a coin flip. Questions about a specific surface? Call the shop. We've been mixing this stuff since 1989.