Vinyl home siding has vulnerable seams in many areas. These tend to occur on corners and around doors and windows. There are also seams between each piece of siding. This will hold up to rain and most other weather conditions, but you shouldn't force a heavy stream of water directly at your siding. You should especially avoid an upward angle - your siding isn't designed to protect your home from water coming in at this direction! Oftentimes, there is no waterproof layer beneath the siding, and a strong, direct hosing may soak the wood frame beneath, causing serious problems.
Before you begin cleaning, there are some precautions you should take to prepare your home. Cover any light fixtures with plastic. Move lawn furniture and other porch decorations away from the house. Lastly, cover your plants and shrubs with plastic as well, to protect them from a deluge of soapy water. Just remember to remove all of the plastic as soon as you are finished. Your plants shouldn't be left in these mini-greenhouses for too long.
The easiest method for cleaning vinyl siding simply involves clean water and dishwashing detergent. Your first step should be to rinse off the siding. Use a garden hose set on a medium mist. Once you have rinsed off the siding, mix dishwashing soap with warm water. This sudsy solution should be enough to clean the dirt and grime off of the siding. Soft brushes on long poles are available from RV dealerships, or you can improvise by attaching your own brush to a pole, or simply using a ladder. Gently scrub with the warm, soapy water, then rinse.
If you have difficult stains, there are a variety of cleaning options available. Vinegar and water make a simple, environmentally friendly cleaning solution for almost any stain. Use about three parts vinegar to seven parts water. You can also use a small amount of laundry detergent or glass cleaner on stubborn stains. If you have discoloration that no amount of cleaning seems to remove, you may need to consider painting your siding to regain that fresh, clean look.
You should never use chlorine bleach to clean your siding. This type of bleach is toxic to plant and animal life. Though you may only be using it on your siding, remnants will seep into the ground water as you rinse it off, and this can be very dangerous. There should be no need for bleach. However, if you are faced with especially stubborn mold or mildew, you can use oxygen bleach. Use a solution of five parts water to one part oxygen bleach. This is a safe, non-toxic alternative.