A leaf screen is a simple mesh with 2–3 mm openings fitted at the gutter entrance or the tank inlet to keep leaves, twigs and debris out of the water, and it needs cleaning monthly or it clogs and the gutter overflows. Make it big and sloped so leaves slide off and water still passes when it is partly covered: a 40 m² roof in heavy 50 mm/h rain delivers 2,000 L/h to it.
Part of Cisterns and Rainwater Storage
A leaf screen is the first filter in a rainwater system: a mesh barrier that stops large debris before it reaches the downpipe, the first-flush diverter or the tank.
A Screen That Blocks Is Worse Than No Screen, Because The Gutter Overflows
Leaves and twigs rot in a tank, feed bacteria and algae, and block pipes. A screen stops them. A screen that fills up stops the water too: rain then spills over the gutter’s edge and is lost, and a heavy storm can be lost entirely. So the screen has to be large and kept clear.
The cisterns page specifies a mesh with 2–3 mm openings at the gutter entrance or tank inlet, cleaned monthly. That size stops leaves and larger debris. It will not stop mosquitoes, so every other opening of the tank (vent, overflow outlet) also needs its own fine mesh (Overflow Pipe).
What You Need
- Metal or plastic mesh with 2–3 mm openings, corrosion-resistant
- A frame that holds it flat and can be lifted out
- Fixings to hold it against wind
- A brush or hand for cleaning
- Access — a place you can reach safely without a ladder in the dark
Method: Fit Wide, Slope It, Clean It
Step 1: Choose the position. At the gutter entrance, leaves are caught before they enter the downpipe; at the tank inlet, they are caught after. Both together is better.
Step 2: Make the screen bigger than the pipe it protects, because mesh area is open area less wire. A screen no larger than the pipe clogs at once.
Step 3: Tilt it so that water goes through and leaves slide off under their own weight.
Step 4: Clean monthly and after storms and leaf fall, lifting the debris off instead of pushing it through.
Step 5: Keep overhanging branches cut back from the roof.
Worked Example
Heavy rain of 50 mm/h (a made-up intensity for illustration) on a 40 m² roof: 40 m² × 50 mm/h = 2,000 L/h, or 2,000 ÷ 3,600 = 0.56 L/s. The screen must pass that. If leaves cover half of the open area, it must still pass 0.56 L/s through the remaining half. The remedy is a larger screen, not a finer mesh.
Common Mistakes
- A screen with no slope. Leaves lie on it and block it.
- No cleaning routine. Monthly is the minimum.
- A mesh too fine on the gutter. It clogs on dust; use the coarse screen early and the fine mesh only at vents.
- Pushing debris down the pipe while cleaning.
Safety
Roofs and ladders
Cleaning gutters means working at height. Secure the ladder, never work on a wet roof, and do not clean a metal roof gutter beside live electric wiring.
What’s Next
- Learn next: First Flush Diverter — the next stage downstream
- Combine with: Settling Chamber — grit that passes the screen settles here