To get rid of large chunks of dirt and debris, it is best that hosing of the tent is done. This will not completely remove the accumalated dirt but will at least help in getting rid of quite a bit of it, subequently helping the machine washing process.
Tents cannot be washed in a regular machine and for this purpose you need to have machines that are specifically designed. You should get one in case you have to wash them regularly and in big numbers. Otherwise, you can find one that is being offered for service on commercial basis and make use of that.
Not all detergents may work on the tents. The regular detergents will get rid of dirt for the most part but may not completely clean the tent. It is best that the tent specific detergents are used for this purpose which are manufactured keeping in mind the nature of the fabric that is used in the tents. Normal detergents may damage the surface of the tent as well and reduce its life.
Make sure that you follow the instructions given on the tent for washing it. The manufacturers are aware of the needs of the fabric that is used and following these instructions, such as the water temperature when washing the tent and the kind of detergents to be used, can play a vital role in giving the tent a longer life.
Before you store the tents, make sure that they have completely dried up. This not only includes the surface but also the inner ropes which are often left wet. Doing so can save your tents from being damaged.