On Oct 10, 11:06 am, MNRebecca wrote:
On Oct 10, 11:45 am, RicodJour wrote:

Is there any water cascading over the front edge of the gutter
anywhere along its length?

Nope. That happened a while back when, to my shock, the downspout
hole in the gutter clogged just two weeks after being checked (and
despite my use of gutter guards) and the gutters began overflowing in
a downpour (after two years of drought, all we get is downpours!). I
scooted up quick and unclogged it. So, when all is clear, the gutters
can handle the load from a downpour, but the downspout, at the elbow,
can't, and the rain shoots up out of the top of the elbow.

The additional info you have provided seems to confirm that the
vertical down spout section coupled with the "horizontal section" (ie
the drain line) cannot handle the flow.

IMO a larger down spout & drain line is indicated. The larger down
spout will be less prone to clogging & and the larger drain line will
give less back pressure to the system.

If you want to get technical, you need the area of the roof that is
drained by this gutter, down spout, drain line combination....armed
with this info AND a estimate of the peak rain fall rates you've been
experiencing (inches per minute or a peak rate of inches per hour
converted to inches per minute)

This will allow you to calc the maximum flow rate through your system

But on the other hand since the gutter doesn't over flow & nothing is
clogged........ you could just seal the elbow joint to prevent the
errant spray and forget about changing anything.

The additional pressure head built up by the rising water in the down
spout (which causes the spray) actually generates a self regulating
system.........the increased pressure increases flow through the drain
line and balances the rainfall run off. Seal the joint & the
immediate issue goes away.

Dry the joint, clean with acetone & seal with aluminum tape. Or a
section of inner tube (or EPDM roofing material) & hole clamps.

It all depends on how you want to handle this.

cheers
Bob