There can be several reasons why rain is coming over the gutter instead of staying in the gutter and exiting the downspout.
During heavy rain water jumpa over the gutter.
Same goes for lack of pitch which causes the water to gather in one spot rather than flowing toward an exit.
However during heavy rain water may not move quickly enough through the foam.
The pitch of gutter heading towards a downspout can also cause overflow if it s too steep.
Think of it this way.
You can find these precut gutter splash guards about 3 in brown and white aluminum at a home center but you could easily make your own out of aluminum or sheet metal and spray paint them to match your gutters.
One is that the gutter is not pitched so the area where the spillover was happening is actually a low point in the gutter.
Numerous people have tried ideas but none have worked.
Holes through the splash guard and the gutter.
This valley shoots rain in a flume during our frequently heavy downpours.
Too few downspouts will tend to make the gutters overflow during a heavy rain.
If the gutter is tilting away from your house it could be causing an overflow particularly during heavy storms.
With surface tension covers leaves slip off the edge while water moves into the gutters.
Currently there is a diverter moved a little way up the valley and black sponge intended for putting inside a gutter has been wired onto the mess guard on top of the gutter.
Surface tension gutter covers conquer heavy rain.
Next is the size of the gutter itself.
First your gutters may be clogged with leaves.
Drill rivet holes for the gutter splash guard.