Cleaning out a rainwater storage tank can be very difficult and time-consuming therefore it is very important to prevent the tank from being contaminated with foreign matter from the roof or gutters, trust us when we recommend spending a little bit extra in this area. One of the biggest things that are often overlooked is the nitrates that get into the water from bird droppings. High levels of nitrates are harmful to humans and very dangerous for infants. You also dramatically increase the chlorine usage if this gets to the tank. Fortunately, a good First Flush Filter like the SuperHead dramatically reduces nitrate levels if configured correctly.