The lower cement 5000 gallon water tank is fed from the roof of the main house via down pipes from both the front & the rear of the house. The water from this lower tank is then pumped up to the higher tank which gravity feeds the main house.
This pump is also a fire pump, it draws water from the stop cock on the side of the lower tank & pumps it up to the higher tank via a pipe that runs underground.
This image shows the two “first flush” pipes on the lower tank. Any dirt on the roof or in the gutters is washed into these two pipes. When full, a ball float in the pipe rises to the top closing off these tow pipes & allows the rest of the water to flow into the tank. Over time, the water in these pipes is supposed to slowly run out via the hoses at the bottom, but invariably the small hole blocks with dirt, so every now & then I remove the bottom of the pipes, drain & wash out the filters.
The garden tank was placed on higher ground to the level of the garden so it would gravity feed better, but this meant that it was too far away from the house to use an overhead down pipe to fill it from the roof at the end of the house. So I run the down pipe underground then back up into the top of the tank.