Wind Impact on Power Washing

Power washing is an effective way to clean the exterior of a house, but not when the wind swoops in and carries cleaning solution into the neighbor’s yard… By understanding the role of wind and how it interacts with water droplets, you can significantly enhance the quality and efficiency of your power washing – especially when tackling high peaks or hard-to-reach corners. The impact of wind on power washing should not be underestimated.

Droplet Size in Power Washing

One of the key functions of a power washing system’s nozzle, aside from pressure control and spray pattern, is to regulate the average size of the produced water droplets. Within a pressure washer nozzle is an orifice (a small hole through which fluid flows); a larger orifice will produce bigger droplets, which are heavier (have more mass) and, consequently, are less affected by wind. Conversely, a small orifice will produce finer, mist-like droplets which are more easily carried away by gusts of wind.

Why Droplet Size Matters

To understand why droplet size matters, we first consider the mass of a water droplet. The mass of a water droplet is proportional to the cube of the droplet’s radius. Since momentum is the product of mass and velocity, larger droplets will have more momentum for the same initial velocity, propelling them further than smaller droplets. This is intuitive, but it’s not quite that simple. Since wind resistance (drag) is proportional to both the cross-sectional area of the droplet and the velocity of the droplet (more intense resistance to faster movement), larger droplets suffer from more energy loss due to wind resistance. Since drag is proportional to the square of the droplet radius, while the momentum is proportional to the cube of the droplet radius, the result is that larger droplets have a higher momentum-to-drag ratio, allowing them to maintain their trajectory more effectively in windy conditions.

A problem arises because droplet size and velocity are both a result of nozzle characteristics. A smaller orifice produces higher-velocity, smaller droplets, making them prone to wind drift. A small droplet size with high velocity results in a double-whammy of energy depletion: the high initial velocity induces higher drag, which has an outsized effect on the smaller droplet mass. In effect, this means that a water stream, as characterized, would be exceptionally susceptible to being carried off course by the wind. Careful nozzle selection can easily alleviate much of this wind-derived challenge. 

Using the Wind to Your Advantage

Rather than viewing the wind as a hindrance, a shift in perspective can turn the wind into a friend.

Align with the Wind Direction

Whenever possible, work with the wind rather than against it. This allows the wind to carry smaller droplets to their intended target, extending your effective reach without additional effort. This is especially true when attempting to clean an extended corner, with wind whipping above and around. Do not fight it - the wind always wins, regardless of which pump your system uses.

Take Advantage of Large Droplets

On windy days, a nozzle with a slightly larger orifice can make a big difference. Larger, heavier droplets are less likely to be diverted by the wind, before reaching their target. Using quick-connect fittings makes quick nozzle changes easy.

Plan for Wind Shadows

Structures and landscaping features can create wind shadows: areas where airflow is blocked or reduced. These wind shadows can be used to your advantage, allowing a stream of water to be uninhibited for part of its travel from nozzle to surface. Keep in mind that significant turbulence at the edges of a wind shadow can produce unexpected flow patterns - minimize transitions through wind shadow boundaries.

Consider Angles

If you are standing twenty feet from the surface, and cleaning twenty feet high, then the distance from the nozzle to the surface is approximately twenty-eight feet. If, however, you are standing five feet from the surface, the distance is reduced to just about twenty-one feet, or only three-quarters. This reduced travel distance means that the wind has less time to affect the water droplets. If you need to reach just a little further, consider a steeper spray angle. Don’t let the wind waste your cleaning solution or bleach the landscape.

Final Thoughts

Wind plays a significant role in the power washing process. The first step to harnessing the wind, to your advantage, is understanding the interplay between orifice size, velocity, and droplet size. From there, spray technique and job planning can prevent wastefully fighting against the wind, while enhancing the effectiveness of any power washing process. Whether you’re a professional or a DIY enthusiast, leveraging wind effectively can save time, reduce effort, and produce superior cleaning results.

Surface Work has it Figured Out

Surface Work has already done the research, built the systems, and developed the processes to deliver fantastic results – every time. Instead of buying a wide range of nozzles, learning about pressure, building out a downstream injection system, and mastering all the practical application tricks - save your money and contact Surface Work today.

From Dam Neck to Diamond Springs, Surface Work operates throughout Virginia Beach (and a little further), while sharing power washing knowledge with anyone who is interested.

Water droplet size plays a critical role in the reach of a power washing system.