It's a slope game. Every run of trough is pitched about 1 inch for every 20 feet toward a downspout. Lose that pitch (sagging hangers, ice load, a ladder leaned in the wrong spot) and water sits in the trough instead of leaving. Sitting water rusts steel, breeds mosquitoes, and in winter it becomes an ice bar that pries the trough off the fascia. The system only counts if water ends up 6 feet away from your foundation. That last part is the whole point, and it's the part most homes get wrong.

Our freeze-thaw cycles are brutal. Meltwater refreezes in the trough overnight, expands, and works seams and hangers loose a little more every winter. Add mature-tree neighbourhoods (looking at you, Etobicoke and East York) where a single fall drops enough leaves to plug every downspout on the street. Most GTA houses also sit on clay, which swells when wet. So an overflowing gutter doesn't just stain siding, it feeds water straight into soil that pushes on your foundation.

Seamless means the trough for each run is rolled from a coil on site, in one piece, cut to your house. No seams except at corners means almost nowhere to leak. 5-inch is standard; 6-inch moves about 40% more water and makes sense under big or steep roofs. Thickness matters too: 0.027-gauge aluminum is the cheap stuff, 0.032 is what you want holding a ladder of ice. Ask what gauge you're being quoted. A low bid is usually thin metal and wide hanger spacing.

Old trough comes down before lunch. Fascia gets inspected, because putting new eavestrough on rotten wood is throwing money away, and this is when rot is cheap to fix. New runs are rolled in the driveway, hung with hidden hangers every 24 inches or less, pitched with a level, sealed at corners and outlets. Downspouts go in with extensions or splash pads. A good crew hoses the roof afterward and makes you watch where the water goes. One day, most houses.