So what exactly is a roof washer?
A roof washer is a device or even simply a method for removal of sediment and debris from collection surfaces shortly after the rain has started to fall. This is usually accomplished by diverting the initial rainfall away from entry into the rainwater harvesting storage tanks or cistern.
The better roof washers will usually have a debris screen. A good debris screen will protect the roof washer from the damage that is caused by waste and vermin. Usually the debris screen should be corrosion resistant.
A good roof washer will automatically divert the first 0.02 inches of rainfall per 24 hour period per square feet of roof area away from the rainwater harvesting storage tanks or cisterns.
Roof washers should be installed in such a way that they will be easily accessible for regular maintenance to ensure that they are working well all the time.
A roof washer makes a great difference in the quality of the water that is harvested. You will not believe how dirty a roof can get within such a short period of time. This is really not surprising when you consider the fact that roofs are prominently exposed to all the elements and will tend to attract dust, leaves, debris, bird droppings and a host of other dirt and grime that greatly impacts on the quality and safety of the rainwater harvested. So by having a roof washer to ensure proper cleaning using the rainwater moments before the water starts entering the storage tanks impacts tremendously on the quality of water you will always end up with.
A roof washer should not stop the excellent practice of physically cleaning the roof just before the rains are due to start. Rather, both methods are supposed to combine to ensure a very high standard of cleanliness on the roof that will harvest the rainwater. Actually the two cleaning methods or systems should work hand in hand for the best results in rainwater harvesting.
There is a huge difference between a rainwater harvesting system that has a roof washer and one that does not have. Although areas and locations of roofs will greatly vary and will impact on how dirty a roof is bound to be, there is little doubt that a roof washer inclusion in a rainwater harvesting system makes a huge difference, wherever the location of the roof is and whatever the circumstances of the environment there.