Rain
Barrels?
A
backflow preventer should keep street water out of your house, but what about
the water at the rear of the house? In most bloomingdale row houses, the rear
roof gutters are connected to downspouts that lead the water into your house`s
sewage drain pipes. If you`re having a flood in the front of the house, the
backflow preventer will close, leaving the roof water nowhere to go but your
basement.
One
proposed solution to this is to direct the roof water into a rain barrel, so
that water collects in the barrel rather than in your basement. Good idea??
Well, only if the barrel is large enough. And large enough is pretty hard to
define.
So
let`s make some explicit assumptions. Let`s assume that a 20`x25` area of your
roof drains into the rear of your house. Let`s assume a rain storm that unloads
3`` water. (The 9/2 storm was, according to DC Water, 2.79``) Your house may be
bigger or smaller, and we certainly can expect occasional rains in excess of 3``.
But I`m going to work with those figures, as an illustration.
Total
roof area in square inches (20x12x25x12): 72,000
Total
volume of water, in cubic inches (3 * 72,000): 216,000
Total
volume of water, in gallons (216,000 / 231): 935
My
conclusion is that typical rain barrels, 55 gal, 80 gal, will not help. They
will fill up early in a storm, during the period when your bfp is open and
storage is not needed. The barrel will be full and overflowing late in the
storm, which is when you need the storage. Even a much more common 1 inch storm
will dump 311 gallons onto this size of roof, and even that is far beyond the
capacity of a typical rain barrel.
There
are also above-ground cisterns that can hold hundreds of gallons. Some mid-sized
ones, in the 400 gallon range, can fit through doors and be placed in a typical
limited-access bloomingdale back yard. The larger cisterns, 1000 gallons and
up, could only be installed in a
limited-access back yard using a huge crane.
And
one more thought. Rain barrels lead to standing water, which is the ideal
mosquito habitat. See this.
So
for me the bottom line is that typical 50-80 gallon barrels won`t help. A 400
gallon cistern is the scale that could help. It won`t collect all the water of
an extreme event, but 400 gallons is significant. Unfortunately, cisterns large
enough to be considered true solutions are simply out of reach, literally, for
most of us with limited-access back yards.
To
read more about rain barrels in DC, try this .
This is a good analysis, and the reality most of us face. It begs the question, what else can we do? Nothing as far as I can tell. We just put in an 80 gallon barrel and diverted our rear downspout to run to it and the overflow pipe goes to our yard. All we can do is hope the water in the yard doesn't then subsequently flood our house anyways, or other houses.
ReplyDeleteOptions within our control pretty much cease to exist beyond this, so this is how our B'dale house is going to roll for now.
This is a key discussion point for which I think the city needs to pay attention because people will continue to find individual solutions to protect their homes. Without a collective solution in a reasonable time frame, all we can do is wait and see if the aggregate of those individual solutions causes more problems then what currently exist. That is why an independent engineer assessment for immediate (within 6-12 months) solutions to close the gap between now and 2025 is of utmost and critical importance.
We live on Thomas st. NW and have a 300 gallon rain barrel which sits unobtrusively in our back yard. When absolutely necessary an overflow hose directs excess water into the alley. Since installing this system, along with a back water valve in our front yard, we have had no basement flooding. It's bee over two years. I would be happy to show anyone in the neighborhood who is interested how our system looks and works.
DeleteMarshall
marshallkeys@mac.com
202-669-6660
Did the 300 gal rain barrel overflow on any of the recent storms that caused Lake Rhode Island to appear?
DeleteThanks Marshall. Reassuring to hear your approach has been successful. Hope ours is. I wish we had an alley to reach our overflow! We could add capacity to ours by connecting multiple barrels too, so we'll have to see how it plays out. Do you have a link to where you got the 300 gallon barrel? My guy at Aquabarrel.com goes from 80 gallons to the Fat Boy 650 gallons, he didn't show me an in between option.
DeleteFor anyone looking to get something quick and close by, Barry at Aquabarrel.com is a little under an hour (w/ no traffic) out I-270 in Maryland. Easy to find. Knowledgeable guy. Prices are right in line with multiple sites I looked at, but you save on what could be very big freight shipping charges for delivery, depending on size of apparatus.
I am looking at the www.aquabarrel.com website. Which rain barrel or cistern do you have?
ReplyDeleteI think this analysis may be missing one big point of having a rain barrel. The RiverSmart Homes program offers homeowners the ability to have a rain barrel installed for $50. The whole point of this program is that while 50-80 gallons might not mean much for the individual home, the more people who install them in the city means less pressure on the combined sewer, which is part of the solution to prevent the system from overflowing in the first place. Planting trees and creating more permeable space (pervious pavers or rain gardens) on one's property are additional components to solving this problem. So if you already have one installed, then you are already doing your part, albeit small, to be part of the solution.
ReplyDeleteThe final reference in the original article, a summary of experiences with DC's Rain Barrel Demonstration Project, directly addresses your point. It's 85 pages, so I'll admit to skimming it. One conclusion was that for the purpose of reducing stress on the DC sewers, a rain barrel program's "cost-effectiveness at this time is somewhat questionable."
DeleteThe report notes that to achieve a "modest" one million gallon reduction in runoff would require rain barrels at 20% of the rowhouses in the district, which would have been 6981 rain barrel installations in 2001 when the report was issued. By coincidence, my guestimate for the size of Lake Rhode Island is about 1 million gallons.
Rain barrels are a good thing and a helpful thing. Yes, work with RiverSmart Homes, which has numerous good ideas on their site, including rain barrels.