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What Mix Should I Use for Soft Washing?

While soft washing relies on the use of a chemical (usually sodium hypochlorite, a.k.a. bleach), a surfactant, and a gentle spray of water to kill organic growth on surfaces, you don’t want to use more bleach than necessary. This not only is a waste of your chemicals, it’s putting the plant life and surfaces at greater risk if you spray with too hot of a mix.

When it comes to your soft wash mix, not all surfaces need the same amount of sodium hypochlorite, i.e., bleach.

The Asphalt Roof Manufacturing Association (ARMA)  says that "The most effective method of cleaning algae and moss from a roof is with a 50/50 (i.e., 1:1) mix of LAUNDRY strength liquid chlorine bleach and water.” 

Note the key word here: “LAUNDRY” strength. This is the bleach you by off the shelf at your local grocery store, and it is only 5.25 to 6% sodium hypochlorite.

Professional-grade commercial bleach like what we sell is a little more than double the strength. That means you need to cut the ratio to around half, which would be 75/25, or 3:1. That’s 3 parts water, 1 part bleach.

Determining Your Roof Cleaning Mix

Because commercial-grade bleach is 12.5%, it’s actually a little more that twice that of laundry bleach, which is why we recommend using no more than a 3% mix. What do we mean by 3%?

Let's Do Some Math



Take the batch size you are using and divide it by 10. For example, if you are going to have a 50 gallon batch: 

50/10 = 5



Multipy 5x3(%) = 15

That means 15 gallons of you 50-gallon batch is going to be 12.5% bleach.



Subtract 15 from 50.

(50 - 15 = 35)

This is how many gallons of water you will use, i.e., 35 gallons

Let’s do another quick example. Say you have a 7 gallon mix:

Step 1: 7/10 = 0.7

Step 2: 0.7 x 3 = 2.1

Step 3: 30% would be equal to 2.1 gallons bleach, 7.9 gallons water (or you can round to 2 gallons bleach, 8 gallons water).

"But I've heard to Go 50/50 with my roof mix!" 

 If you look around on industry Facebook pages or forums, you may find guys talking about how hot they go with their roof cleaning mix. A lot will use 50/50 (or 1:1) with their bleach to water mix. 

We don't recommend doing this. Here's why:

1. It's too hot!  Remember, ARMA's recommended mix is 50:50 for use with LAUNDRY bleach. That's only a 5-6% bleach mix to start with. Commercial grade is over twice that much! 

2. It typically doesn't clean better. In most cases, 3% is plenty to get a roof cleaned, especially if you're using a great surfactant like Sticky to help your solution cling to the surface and dwell longer. 

3. You're wasting money. If you are increasing your sodium hypochlorite mix to 50/50, you're losing money. Say, for example, you're buying commercial bleach for around $3.50 per gallon. If you mix a 50-gallon batch, you're spending $35 more on bleach than you would by using 3%. Two jobs like this per day, 5 days per week = $350 extra per week spent on bleach that wasn't needed!

4. You're increasing your risk of damaging plants. If you kill plants, you are either going to have to replace them out of pocket or file an insurance claim. Either can be costly. 

If you have a super dirty roof, you are better off going back and hitting it twice – or at least spot cleaning certain areas – than hitting it that hot.

What's the right soft washing mix for siding? 

Houses generally do not get as dirty or have as much organic growth as roofs, and therefore do not need as strong of a mix. We generally recommend using a 1% mix on most siding. 

Again, let’s do the math for a 50-gallon batch.


5 x 1(%) = 5

So your mix would be 5 gallons of bleach, 45 gallons of water.

Automating the Soft Wash Proportioning Process

None of this takes into account adding in your surfactant. You can see why having a soft wash system like the ProTool Clever or Batch Pro that automatically doses for you is beneficial. With the Clever and Batch pro, you just dial adjust the dial and the system does all the math for you!