On Oct 11, 8:48 am, "Dave" wrote:

So, the water rising/gushing out is in fact coming from a joint in a
horizontal guttering that was never meant to move water horizontally and in
such substantial manner.


I suspect the (essentially) 90 degree angle of the elbow, coupled with
its narrowness, is a large part of the problem. I thought to myself,
"What if I found a wider, longer, flexible elbow, so that the heavy
flow of water didn't have to make such a narrow, tight turn? Maybe I
could hack off a bit of the downspout and make the turn into the
horizontal pipe more gradual, less constricted." The fountain effect
is happening right above the top of the elbow, after all. But crap,
the downspout is anchored to the house way down low, so low there's no
room for anything but a 90 degree turn. I'm not crazy about the idea
of abandoning the use of anchoring (it's a windy area on that side of
the house)... or of drilling new screw holes higher up (it's REALLY
windy on that side of the house).