Home>Discussions>EXTERIORS>Rain Gutters -- Handling Heavy Rains
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Brookworld
Rain Gutters -- Handling Heavy Rains

Hello: my rain gutters seem to be overfilling more frequently than normal during heavy rains.

I recently moved into a 1965 house with the normal set up of down spouts on the 4 corners. The house footprint is 55 x 35 and I assume the house is designed with rain gutters & 4 downspouts that can collect and drain water in a “normal” rain, but the “system” would be overpowered by a “heavy” rain. In Northern Virginia, average rain is 3-4” EVERY month and with high humidity, thunder showers are more common than just “steady” rain. However, it doesn’t seem right to see water pouring over in heavy rains and we’re concerned about unseen damage/rot from this.

I do have some issues: the house is on a down slope and thus, the basement is walk-out on the back. The 4 down spouts tie to an underground drain system of some sort. We checked the gutters and they look clean; a handyman also ran water down the spout and it appears to be draining (although I don’t know the rate or amount of water being used). Where it is overfilling, we took the downspout off the underground drain because we suspect the drain pipe was made from clay/ceramic and it may have collapsed in some areas or gotten clogged. Still, in heavy rain, the gutters overfill and water pour over.
The previous owner said he replaced the gutters 7 years ago and I assume they were done properly.

Heavy rain also doesn’t always happen at daytime when I can get a better look at what’s happening. What are the steps to take to diagnose the problem?

A. Spruce
Re: Rain Gutters -- Handling Heavy Rains

My suspicion is that the problem lays within the downspout conduits themselves.

The most common manner of making downspouts is to take a long length of conduit and cut a "birds mouth" for each of the bends. The upper part of the conduit is folded into the lower section to direct water down the conduit. The problem with this method is that it effectively reduces the inner diameter of the conduit significantly, as well as creates places for debris to catch, further restricting the conduit and causing back-ups..

The first thing I'd recommend is that you remove the downspouts and back-flush them by running a garden hose up from the bottom. Allow the conduit to fill with water before lifting the bottom end above the top inlet and rapidly washing out the conduit. This head of water will push out any debris that is there.

This should cure the problem for the moment. If you want to fully rectify the issue, then you need to purchase 45* or 60* conduit elbows to replace the existing cut/bent elbows. Once you've got a full dimension conduit running from top to bottom, you shouldn't have any more overflow issues.

One other thing to check is how level the gutters are. I've seen some so far out of whack that one end will overflow before the water can reach the downspout on the opposite end. In cases like this, I add a downspout to the low end. If you've got downspouts on each end of long runs such as this, and you've ruled out blockages in the conduits and drains, then adding another downspout midway in the length of the gutter would be helpful.

Cougars1996
Re: Rain Gutters -- Handling Heavy Rains

Our house, when the addition was added, came up to 64' end to end. Because of the location of the driveway, septic and regional restrictions on plumbing collected rainwater towards where the septic leach field is, we had to direct the front gutter to one side of the house and do the same with the rear gutters. In each case, all 64' of gutter (typical size) drains into a single downspout (one on the front of the house, one on the back).

The roofing contractor who did our gutters worked on the problem of overloading the downspouts by putting what he called "commercial size" downspouts (4" x 6") on each gutter. He also cut the drain holes in each gutter as large as he could manage.

So far, with torrential rains during thunderstorms (sometimes 0.5" or more in a few minutes), we've never had any problems. Our downspouts drain well away from the house onto ground that slopes away, so we know that the gutter/downspout arrangement works in this case. I hope this helps.

Good Luck!

:)

HoustonRemodeler
Re: Rain Gutters -- Handling Heavy Rains

Down here in Houston we get 1" of rain an hour frequently. The larger gutters AND downspouts are the way to go.

Some might call them commercial sized, but round these parts we think of them as standard Texas sized.

dj1
Re: Rain Gutters -- Handling Heavy Rains

Guys, I'm jealous: I don't even have gutters.
in LA, gutters are not required, they're optional.

A. Spruce
Re: Rain Gutters -- Handling Heavy Rains

That's what you get for living in LA! :p:D;)

dj1
Re: Rain Gutters -- Handling Heavy Rains

Spruce, no complaints, really. We average 14" of annual rain, but there are so many years with much less...I don't know what kind of average it is. Maybe imaginary average. :D

A. Spruce
Re: Rain Gutters -- Handling Heavy Rains

There's lots of things in LA that are imaginary, aren't there ... ;):p

dj1
Re: Rain Gutters -- Handling Heavy Rains

They don't call it LA LA LAND for nothing.

Brookworld
Re: Rain Gutters -- Handling Heavy Rains

First , thanks guys, Spruce & Cougars . . .

. . . . the problem lays within the downspout conduits themselves.

The first thing I'd recommend is that you remove the downspouts and back-flush them by running a garden hose up from the bottom. Allow the conduit to fill with water before lifting the bottom end above the top inlet and rapidly washing out the conduit. This head of water will push out any debris that is there.

ME: this will be hard to do; the house is brick all around (not brick veneer) and downspouts are nice copper (with green patina). I think I may have something like 4 x 4 size downspouts – the house was built by a neighborhood builder for his retirement in 1965 so it’s custom but not “old world”. I wonder whether there is debris in the elbows/bends. The elbows/bends appear “crimped”, so I will check whether there are “full openings” there. I also wonder if ‘snaking” the elbow/bends from the top (with downspout still attached to the wall) will also do. As a middle age sole breadwinner in the family, I can’t be climbing high ladders ).

The roofing contractor who did our gutters worked on the problem of overloading the downspouts by putting what he called "commercial size" downspouts (4" x 6") on each gutter. He also cut the drain holes in each gutter as large as he could manage.

ME: will check the drain holes. We have original 1965 copper downspouts, so can get expensive.

A. Spruce
Re: Rain Gutters -- Handling Heavy Rains
Brookworld wrote:

The elbows/bends appear “crimped”, so I will check whether there are “full openings” there.

Those 4x4 downspouts should be able to handle the flow just fine, especially if they are full dimension through the elbows. By crimped I'm assuming you mean like this, which would mean that they are indeed full dimension.

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