This Common Pressure Washing Mistake Leaves Streaks and Spots

While a warm sunny day may seem like an ideal time to pressure wash, it’s actually one of the worst times to do it. If you choose to pressure wash on a hot sunny day, you’re liable to end up with spots, streaks, or even uneven patches of clean and dirty spots, whether you're washing your house, car, or driveway. 

Related: This Pressure Washing Mistake Can Ruin Your Concrete Fast

Why Sunlight And Power Washing Don’t Mix

The reason sunlight and power washing don’t mix has to do with the two step process of power washing. Power washing involves applying soap then following up with a rinse. It’s that first step that gets thrown off by sunlight. When you powerwash on a hot sunny day, be it your car, driveway, or house, water quickly evaporates on those warm surfaces, often before you have a chance to rinse it off. When that happens, the detergent leaves streaks and residue on the surface, which is particularly visible on vehicles, siding, windows, and even driveways. 

Cleaning Detergents Don’t Work

Cleaning detergent needs time to soak into and cut through grime and dirt on the surface. If it dries too quickly, it won’t be effective at doing this. As a result, you may end up having to clean the same area several times to remove dirt. 

Water Evaporates Too Quickly

The soap isn’t the only thing that can leave residue behind. When water dries too quickly, it leaves behind mineral deposits that create a visible water mark on siding and cars. 

Can Cause Damage

Spraying high pressure cold water on a hot surface can also potentially damage or discolor siding due to thermal shock. It can strip wax off a car’s finish or even damage the clear coat. When vinyl siding is hot, it becomes more pliable and hence more susceptible to damage from a high pressure spray of water. 

The Best Time to Pressure Wash

For best results when pressure washing, wait until whatever surface you plan to clean is cool and out of direct sunlight. With that in mind, the best times to pressure wash are early morning, latter afternoon and evening, and on overcast days. 

Related: Pressure Wash Pavers Without Destroying Them

Bottom Line

Given how time consuming and labor intensive pressure washing is, it makes sense to perform this task when you’re going to get the most benefit out of it. Get this job done when the sun isn’t shining directly on the surface you’re cleaning. If you absolutely have to power wash when it’s sunny out, try to focus on shaded areas. For areas in direct sunlight, rinse quickly before the soap has time to dry on the surface.