In this case, a splash guard is needed, or what is also called a splash guard. It's a small L-shaped piece of vinyl, or whatever material the gutters are made of. The roofer can install it inside the outer edge of the gutter, just in the corner facing the end of the valley. The idea is that the water hits the protector and falls directly into the gutter, where everything should have been the weather.
To prevent rain from overflowing a gutter that is clean and properly sloped, you may need to look for a wider gutter. Homes that are in areas with frequent heavy rains are often equipped with a wide gutter to collect streams of water before they spill over the edge. If you only experience overflows during intense storms, a narrow gutter is likely to be the problem. The velocity and volume of the water extend across the top of the gutter.
You can make a lock in the inner corner of the gutter that is higher than the top of the gutter. I have used a waste gutter to cut and fold a computer about 3 inches tall that I place on the top folded edge of the gutter. You'll have to go 6 to 8 inches each side to get out of the corner. First check the downspouts when it rains to see if water enters through them.
If no water comes out of the downspouts, then they are clogged. You can determine if this is a slope problem by checking if the overflow occurs near a drain. In loose gutters, you can usually see a space behind the gutter. If you check those 3 items off the list, then you're left with dripping problems.
If yours is a U-type gutter, attach a type I gutter so that the upper part prevents water from overflowing when it rains a lot.
