Soft washing relies on the power of chemical reactions to deliver exceptional cleaning results. Similar to pressure washing, excessive “cleaning power” can lead to damage; this is why any power washing task requires consideration of the cleaning triangle: Time-Chemical-Pressure. While it’s difficult to provide a one-size-fits-all solution, the following guidelines can help inform effective and responsible soft washing practices.

This is Part 1 of a two-part series. Part 2 will discuss the use of surfactant.

Bleach Use and Misuse in Soft Washing

Understanding Sodium Hypochlorite

The term “bleach” often refers to sodium hypochlorite, commonly found in household laundry products at concentrations around 6%. As anyone who has accidentally spilled undiluted bleach can attest, this cleaning agent is incredibly potent and demands careful handling.

In soft washing, bleach is a staple chemical due to its oxidizing properties, which make it exceptionally effective at eliminating green algae, mold, mildew, and other organic growths. However, proper application is key to achieving the desired results without causing unintended damage.

Best Practices for Using Sodium Hypochlorite

Dilution is crucial

For most grasses and landscaping plants, sodium hypochlorite runoff should not exceed a concentration of 200 parts per million (PPM). Concentrations above this threshold can stress plants, while significantly higher levels may cause widespread damage or plant death.

Since sodium hypochlorite is typically give in a percent concentration, to convert this to ppm, simply multiply my 10,000.

For example: 6% = 60,000 ppm.

To dilute 1 gallon of 12% sodium hypochlorite down to 200 PPM, you would need 600 gallons of water. However, in practical soft washing applications, much of the sodium hypochlorite reacts with organic materials on the surface being cleaned, reducing its active concentration in the runoff. In typical scenarios, around 80% of the chemical is consumed during cleaning, which means the solution needs to be diluted with at least 120 gallons of water per gallon of bleach to mitigate environmental effects - assuming that the cleaning solution is applied uniformly and not excessively.

Practical Dilution Guidelines

When cleaning vinyl-wrapped homes, 1 gallon of 12% sodium hypochlorite is generally sufficient to clean 1,000 square feet of surface area. Conveniently, there is a strong correlation between vertical wall surface area and house floorplan area, which was determined based on analysis of a wide range of house floorplans and structure geometries.

For example: 2,500-square-foot house: Requires approximately 2.5 gallons of bleach, which in turn needs about 300 gallons of water for proper dilution.

For a system operating at 4.0 GPM (gallons per minute), this would require 1 hour and 15 minutes of rinsing. Even with a commercial system running at 8.0 GPM, it would take at least 40 minutes of continuous rinsing to sufficiently dilute the chemicals and protect the landscape. This is just rinsing time.

Cutting Corners: A Cautionary Tale

Any contractor who completes a soft wash on a 2,500-square-foot house in less than an hour is likely cutting corners. Insufficient dilution or rushed rinsing is a common cause of landscape damage, with grass and plants being burned by excessive sodium hypochlorite runoff. Additionally, an improperly chosen cleaning solution concentration often leave homes with a lingering bleach odor for days, indicating poor chemical management.

By adhering to proper dilution practices, contractors can achieve excellent cleaning results while protecting the environment and preserving the health of surrounding landscapes. Bleach will be the cheapest branch of the Time-Chemical-Pressure cleaning triangle, but it should always be minimized in favor or taking more time.

Concentration and Temperature Drives Reactions

The concentration of a bleach solution significantly impacts its reactivity, with higher concentrations driving reactions more aggressively. For example, a 2% bleach solution cleans more than twice as fast as a 1% solution, as the elevated concentration sustains reactivity throughout the cleaning process.

Many power washing contractors use very high concentration bleach solutions so that rinsing can immediately follow cleaning solution application. Unfortunately, this practice inevitably leads to destroyed landscapes, chalky vinyl siding, and hard water stains on glass. Meanwhile the contractor saved a bunch of time…

In contrast, a safer and more professional service balances chemical concentration with factors such as temperature and the density of organic growth on the surface being cleaned.

The Role of Temperature

In the hot summer months, bleach use can and should be minimized, as the increased temperature drives the reactively of the cleaning solution way up; however, this higher temperature results in much faster evaporation, which must be controlled (do not let cleaning solution dehydrate in the sun).

The reactivity of sodium hypochlorite approximately doubles for every 10°F increase in temperature. This makes temperature a critical factor in determining how much bleach to use:

• Summer Months:
  During hot weather, elevated temperatures drive the reactivity of bleach solutions, reducing the need for higher concentrations. However, the faster reaction rate is accompanied by quicker evaporation, which must be carefully managed. Allowing the cleaning solution to dry in the sun not only reduces its effectiveness but also increases the risk of damage to surfaces.
  Best Practice: Use lower concentrations of bleach and keep surfaces wet to prevent dehydration of the cleaning solution.

• Winter Months:
  Cooler temperatures suppress bleach reactivity, requiring slight concentration increases or extended dwell times. For example, instead of rinsing 10 minutes after application, wait 20 minutes to achieve comparable results. Cold air is typically drier than hot air, so evaporation must still be monitored, especially in direct sunlight.
  Best Practice: Work at a slower pace, allowing the solution to work effectively without overcompensating with much higher bleach concentrations (which can also damage equipment).

Surface Work Eliminates Guesswork in Soft Washing

Having completed hundreds of house washing services since 2022, Surface Work has the experience and passion to deliver fantastic results - every time. Whether you live in Kempsville or Lynnhaven, Surface Work has likely already provided exceptional service to some of your neighbors in almost every neighborhood of Virginia Beach.

Don’t waste your time buying and figuring out a new power washing pump system that only gets used once per year… contact Surface Work, kick back, and relax.