Most products used on plants are affected by rain or irrigation but surprisingly few companies test their products for these effects. We have a high precision rainfall simulator. This machine can apply rain accurately to pots containing soil and/or plants. The rain falls for 3,000 hypodermic needles fitted into a header tank more than 5 metres above the target. By falling 5 metres droplets achieve terminal velocity, which is critical to allowing droplets to reach their maximum impact energy. The rain covers an area of about 2m x 1m. The target plants or soil are put on to a slow moving, conveyer belt that passes through the rain. The speed of the belt can be adjusted to produce the required period of rain. The head pressure in the tank can also be adjusted to control the intensity of the rain. Contrary to what many people think, we have found that almost all products that have problems with rainfastness do so with the first 5mm of rain. This equipment is also used to test soil wetting profiles and leaching. This is particularly relevant to soil applied products.