Q. Our new home’s underground sprinkler system sprayed on two windows and the siding. There are no yellow or orange deposits of iron, just white water stains. What can I clean them with?
– JR, Grand Rapids
A The water marks you see are actually hard water minerals dissolved in the groundwater. They are left as deposits after the water has dried. Homeowners who lack a water softening system are used to seeing these white spots on faucets, sinks, and countertops.
Since the minerals are mostly alkaline, the best way to remove them is to use the opposite chemical: an acidic solution. Inexpensive distilled white vinegar, available in half or whole gallons at your grocery store, is acidic enough to break down the hard water stains, but mild enough not to hurt the siding. Even so, you should try the stain removal method on a siding or in a secluded area if it affects the color.
To remove the water marks, spray some vinegar on it, let it sit for a few minutes, spray a little more, then use a non-abrasive scrub pad or soft-bristled brush. If the debris isn’t soft enough to remove, you may need to let the vinegar sit longer.
For particularly problematic spots, temporarily tape some paper towels to the siding, soak them in vinegar, and press them so that they stick. Leave everything in place for a few hours, then remove and rinse off the stains immediately.
One thing you’ll likely notice is that cleaning up the hard water buildup creates a stain that looks different from the siding surrounding it. This is because in addition to the mineral residue that you remove, dirt and other material that has fallen and stuck on the siding since installation will also fall off. So prepare for the possibility of washing an entire side of the house to even out the color.
In a single story home with good siding access, this isn’t a difficult or arduous task – and it makes the house look like a million dollars when you’re done. Two-story homes or those built on sloping land may be more of a challenge to get to the topmost portions.
You probably already have most of the supplies you’ll need for the project: ordinary dish soap, a bucket, a hose with a spray head, and a soft-bristled brush. However, it is worth getting a long-handled brush as it will help you avoid bending over or stretching the lower and upper siding.
To avoid streaks, start washing from the bottom and work your way up the side of the house. First dampen the siding, then scrub it with a soapy water solution. Most of the dirt will fall off immediately.
Mold stains may require a little more scrubbing and possibly the addition of a little TSP (trisodium phosphate, a heavy duty cleaner used by professional painters to prepare surfaces for painting).
After cleaning a section, flush the hose. Do not let the cleaning solution dry on the siding.
Remember that the vinyl siding is designed so that water doesn’t fall down from the top. Training the hose to shoot water up into the ground or into the vertical overlaps of the siding can cause leaks. So always rinse – carefully – from top to bottom, otherwise rain would come up.
Zolton Cohen is a former ASHI certified home inspector based in Kalamazoo. Write to Zolton Cohen, Home Services, PO Box 2007, Kalamazoo, MI 49003.