Sweep all debris from the roof and gutters leading to the chosen downspout by using a broom.
Cistern no gutters.
A cistern is an underground tank for storing water.
Rainwater harvesting is collecting the run off from a structure or other impervious surface in order to store it for later use.
If you join too many downspouts before they enter the cistern you could have a constriction that would be problematic.
Put them where they need to be.
The cistern typically located underground may be constructed of various materials including cinderblock reinforced concrete or precast concrete fiberglass or steel.
It is more important that you have unrestricted flow into the cistern.
Cistern covers are 2 x2 and are cast in the floor.
Remember that the x section of a 4 pipe is twice that of a 3 pipe.
The rain will collect in gutters that channel the water into downspouts and then into some sort of storage vessel.
This is a cistern i made from some pressure treated 2x6 material and a 55 gallon plastic juice drum.
I chose to use 2x6 material because i had it handy but if you choose to u.
Install standard size mesh gutter covers over the entire gutter that will lead into the cistern.
Traditionally this involves harvesting the rain from a roof.
The water was collected from the roof gutters.