Tried to walk the dog between storms yesterday and got caught in a
downpour which yielded unexpected results. I saw something I might
otherwise never have known about. When the rain comes down really
hard, water backs up out of a downspout elbow, shooting into the air
like a fountain (to land in a vulnerable, leak-inducing area) instead
of continuing along the long, extended horizontal downspout track* to
drain away from the house/foundation. Before I look into wider
downspouts and elbows, I'd like to try sealing thoroughly. What will
work better, duct tape or gutter sealant?
*Downspout runs the length of the house, about 40 feet (with one
additional 90 degree turn besides the elbow) before spilling onto the
lawn to run down a hill. This was necessary as the neighbor's
property, just a few feet away, slopes down towards my house. No room
to effectively release water without navigating the length of the
Downspout components are generally not sealed. You have to clear the
blockage and there won't be a need to worry about a sealant.
That is a horrible setup. If you have to dig a drywell to handle the
rain water, then that is what should be done.
If your gutters clog frequently - with a 40' run and a 90 degree bend
I'm sure they do - you should definitely have something like Leafguard
gutters so they won't get clogged with leaves.
Larger downspouts will sure help. If you have the standard 2x3 size, you can go
to the 3x4 size. If the 40' horizontal run is not real visible, replace it with
pvc pipe. I have a similar situation, I use 4" pvc to run 36' across the front
of the house, but it is under the porch so it doesn't show.
You don't have a sealing problem, you have a "blockage problem".
Forty feet of "downspout", really drain line, and two elbows are
probably a little excessive...so the water is backing up &
pressurizing the joint that you see spraying water. You could (when
its dry) seal the joint wiht aluminum tape but that's only fixing the
symptom. You need to make sure your the drainline portion of your run
is free of obstruction & when clean, it is able to handle the
If cleaning (bust open the joint & blast the drainline clean with a
hose) fixes the problem, you're done. If not consider replacing the
drainline portion of the "downspout" system with a 3" or 4" plastic
drainline. Dump the real downspout into the new drainline. Ideally
you'll need ~10" of drop for the drainline....if you have less, this
might be the cause of the backup.
If you go with the drainline fix, use a sweep T fitting with a
cleanout to make maint easier.
Thanks, all, for the help. I'm intrigued by the idea of a T sweep
fitting, something easier to clean than the elbow I'm going to have to
pry loose (not much give built into the system I set up). Dave, the
downspouts never point up (as I understand your question).
Then its confusing to me how the downspout is shooting into the air... IE
V E R T I C A L.
Can you further define what you're saying???
If you don't have enough downspouts to accomodate the gutter, it will
overflow during a heavy downpour. Doesn't matter about outlets to ground
system drainage and so forth. It will only confuse the location of the
actual problem if unaware of that. Dog chasing his tail, if you will.
Based on what she has posted as answers to others' questions, I
believe she has a situation with marginal downspout & drain line
In times of heavy rain, the water backs up in the down spout due to
drainage restriction from that 40' horizontal drain line section.
When the water backs up into the down spout, the down spout / elbow
joint is submerged & pressurized. Due to this pressure, the water
squirts out the joint.
She says she doesn't get gutter overflow, this is because as water
rises in the down spout the pressure heads increases & thus the drain
line flows more water.
She has a situation that seems to work, except for the water squiritng
out of the joint.
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.
Maybe some adaption to 4" drain pipe in the picture might alleviate the back
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).
Don't be too hasty to make permanent changes.
Of course I cannot see your installation from here but I doubt that
the elbow alone is all (or even most of the problem)
Any chance of a picture?
I'd put my money on the 40' horizontal run. I mentioned this
earlier but I think it got missed......how much elevation change does
the drain line have over the 40 feet? It needs about 10"......5"
could work but without sufficient, drop the water won't move very
You say the down spout is anchored "way down low" does the land fall
on the way to the lawn?
Um... none. The downspout goes all the way down the wall of the house
and gets anchored to the house about 9 inches above the ground.
There's just enough room to attach a 90 degree elbow, which attaches
to the LONG horizontal 'pipe' (actually several sections of extra
downspout linked together AND making 1 additional 90 degree turn). I
sure see your point.
on 10/12/2007 12:28 PM MNRebecca said the following:
Not good. Just think how fast, or slow, the rain runs through the
gutter, and the gutter has, or should have, a pitch.
The water in the horizontal section has to be pushed out, more or less,
by the following water, rather than just running out on its own.
Also, the horizontal section is more likely to be clogged by debris
washed down in light rains.
I think we know all the information we need to diagnos & make
Like I said before you need 10" (more or less ideal) or 5" absolute
minimum to make your gravity feed drain line work. The water that
backs up into the vertical section of the down spount is creating the
prssure to make the system work....but it also causes that errant jet
1) seal the joint with aluminum tape (eliminate the jet spray) &
forget about it
2) cut the down spout about 10" shorter and give the drain line
section some slope.
either method will work
Well, I checked for blockages last night. None. I confess I'm a
little bummed. My house isn't that big... 1,800 sq. feet. Is it
logical that even a smaller home can have 'too much roof for the
gutters' in heavy downpours? By the way, Dave, the roof is shingled
with shangle shingles. The part where I'm presumably getting more
water than standard downspouts can handle is an area with a cathedral
ceiling over 2 inside vaults (one over a dining room and one over a
living room whose vault is perpendicular to the adjoining dining room
If you're sure there's no blockage anywhere in the downspout (or where
it enters the ground, if it drains underground), that simplifies
things. You need a larger downspout and possible a larger gutter as
well. You can have a handyman cut a larger hole where the existing
spout is now and fit a 3x4 downspout to replace the existing 2x3.
It's kind of hard to believe that the original installer would think
that a single 2x3 spout could handle 40' of roof. Typically there are
two 2x3s on a 30' run, so you're close to a 2/3s undersized downspout
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.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.