I have only washed an air filter 1 time and vowed never again.
Heating, Ventilation and A/C systems have some type of a/c filter in them.
The air filter function is to catch dust from going into the system. After a week of use, the filter gets clogged. Most air filters are then tossed and a brand new 1 is put in the system. To save money, there are washable filters. You can take out this filter, clean in the coils and reuse it up to multiple times. Air conditioning filters are not that costly. They can range from $5-30 dollars at your local hardware store. I only tried a washable filter because I hated making the trip to the store. The work involved with the filter was not worth it though. First, you have to remove the filter from the system. It is work getting out the metal case that holds the filter. Then you need to take the filter out of the holder and then remove the surrounding materials. After you get the actual Heating, Ventilation and A/C filter, the metal needs to be cleaned. I realized I did not have the common tools to clean it. The small holes had tons of gunk in it and water just ran through them. I had to remove the gross stuff by hand. It took forever and was awful. At the end of it, 30 bucks and a trip to a hardware seemed easy. I buy the Heating, Ventilation and A/C filters in bulk and store them too, and every week I am cheerful to toss and get a new filter.