Most of what you will be dealing with will be mold, mildew, algae, dirt, cobwebs, bird droppings and bug fecal. Other contaminants not as noticeable are exhaust emissions from cars, trucks, airplanes and such. Also anything any nearby factories may be putting out will also land on your home.
The Vinyl Siding Institute (VSI) recommends using the following for small spots of mold or mildew. Small spots of mold and mildew can be handled with cleaners such as Fantastik or Windex. For larger sections, a solution of vinegar (30%) and water (70%) has proven successful. Alternatively, you also could try the following solution: 1/3 cup (2 2/3 ounces) powdered laundry detergent (e.g., Tide, Fab, or equivalent), 2/3 cup (5 1/3 ounces) powdered household cleaner (e.g., Spic & Span, Soilax or equivalent), 1 quart (32 fluid ounces) liquid laundry bleach, and 1 gallon (128 fluid ounces) of water.
In my opinion, the only way to kill and remove mold and mildew is to use the bleach solution. Its important not only to remove it but to kill it as well. If you've ever cleaned mold or mildew before with just water you know it looks good at first but it returns in a short time, that's because it was never completely killed.
Something else you need to know is that bleach is for killing and removing mold, mildew and algae but does not clean well. For dirt and grime you will also need soap in your house wash cleaner. You can use the laundry soap like recommended by the VSI or add a few squirts of dish soap to your bleach mix.
Now you have a home cleaning recipe that will take care of most anything on your home. It can be applied with a brush or sponge. You can try using a pump up sprayer but bleach is corrosive and will eventually ruin the sprayer. It may work long enough to get the job done and if you rinse it thoroughly it may last even longer.
Remember that if you're going to use your pressure washer's chemical injector to apply the cleaner, it will be diluting your mix quite a bit. Most injectors draw only 1 part chemical to 5 or 6 parts water. You can do the math and try making your initial solution stronger and see if you can get good results.
Once you've found a good solution, it should do most of the work for you and you will only need to rinse the area clean. After applying the solution allow it to dwell for a few minutes and then use your garden hose or a pressure washer using no more than 1000 psi and a wide fan nozzle to clean the area. Try to spray straight at eye level with the siding or you can force water underneath and behind it.
It's important to rinse from top to bottom and to be thorough as to not leave any residue on your home. You can add some dishwasher rinse aid like Jet Dry to your mix if you want. An 8 oz bottle will treat 5 gallons of cleaning solution, this will help the water sheet off the siding.
The bleach, water, soap and rinse aid (optional) cleaning solution will also work well on aluminum and painted wood siding. It can also be used for vinyl fences, plastic decking, painted shutters, lawn furniture and most anything else that is exposed to the elements and is covered in dirt, mold and mildew.
Make sure when working around your plants and shrubs that you wet them down with water before, during and after the cleaning process so no solution is allowed to dry on them. The same goes for your windows, don't allow the solution to dry on them and you'll be fine.
Also wear eye and hand protection and a ventilation mask when dealing with bleach. Never mix ammonia with bleach or anything else you aren't sure of.
The industry of pressure washing or power washing has never been considered, by most, to be a serious profession. With typically low start up costs, many fly by night companies come and go leaving a bad taste in the mouth of many unsatisfied customers. It happens in all industries, but the pressure washing industry seems to attract almost anybody out of a job or sick of working for the man.
A couple hundred dollars and a trip to the local home improvement store to purchase a pressure washer, and they are in business. They hit the road running with the attitude that they are going to be the next millionaire. On a shoestring budget, they print up their own fliers to hang on telephone poles and go knocking door to door asking for work only to be let down by an enormous wave of no's.
To combat their lack of marketing and sales knowledge, many of these companies fall into the trap of offering a lower price than the competition, or low balling in a desperate attempt to get work. They offer ridiculously low prices and then have to take short cuts in order to make a profit. Many of them can't afford general liability insurance or workman's compensation insurance so they operate without it.
With their less than mediocre equipment and knowledge, they damage your property and give you a horrible service. Some of the horror stories my customers have told me about their past experiences with one of these types of companies are disturbing to say the least. From blowing out people's window screens to leaving wand marks all over their vinyl siding or scarring up their expensive decks to putting an inferior sealer on it.
I've heard it all and the scarier part is; what have these kinds of companies done to their property that they didn't see? Things like forcing water in behind the vinyl siding by using too much water pressure or using only water to clean the home, meaning the mold and mildew would return in a few months because it was never killed and because they did not apply a protective wax to prevent re-growth. I've heard of some unethical contractors cutting their customers deck stain 50% with mineral spirits to cut down own their costs.
Some even skip the important step of wood brightening or neutralizing during the wood restoration process. All this boils down to giving the pressure washing industry a bad image, which breeds more fly by night companies with the misconception that pressure washing is easy and that anybody can start up with a few dollars and do it. It also forces a lot of homeowners to result to doing their own pressure washing which can be dangerous and definitely painstaking.
The pressure washing industry, in my opinion, is in need of an organization or association that could require contractors to become licensed. Such an organization could set in place rules and guidelines and offer testing and membership opportunities. This would help homeowners in choosing only a reputable company that would meet these guidelines or that were licensed. There have been attempts by organizations in this industry in the past, but their focus has gone off course and contractors have turned their backs on them.
There is a ban of reputable pressure washing contractors, spread out all over the country that I believe are the future and possibly only hope of this industry. They network by internet, phone, informal meetings, conventions, and round tables during all times of the year. They provide free information to each other and to new contractors interested in pursuing a career in pressure washing.
Many have participated in what they call "labor for learning" where they invite a new, inexperienced contractor to come and work with them, and unselfishly show them the ropes in trade for some labor. This is a great concept because there is no better way to learn something than by hands on experience. Others have also given away free valuable information through formal and informal presentations at round table meetings, helping to shave years off of the learning curve of newer contractors.
Many also give away their knowledge by participating on message boards on the internet, helping others on a daily basis. They network together to hone their own skills and to teach others the correct methods and techniques that are involved in providing a quality pressure washing service.
This is all in an attempt, by people who are passionate about what they do, to solidify the professionalism of the pressure washing industry in the eye of the public.