Dry Well
Talk to Greg Pillori http://www.pilloriassociates.com/projects/
Guest User | 3 years and 8 months ago
14
Please log in, in order to post replies!
14 replies
JoeBushwick | 3 years and 8 months ago
Has anyone installed a dry-well in their backyard to manage storm water coming off a flat roof? In the recent storm, the main house drain became overwhelmed and backed up in the basement. Any recommendations for contractors or costs would be appreciated.
JohnHancock | 3 years and 8 months ago
Someone on here before mentioned this a while back, perhaps Master Plumber or one of the other plumbing experts. Dealing with the excess water when a check valve is in place. Maybe someone remembers or check the archives but we’re dealing with a LOT of water coming off your roof so the drywell has to be pretty big
stoopsitter | 3 years and 8 months ago
FWIW, we have a large gravel oval in the middle of our backyard with about 6” of sand below the gravel. It acts as a very efficient dry well for excess water and we never having standing water. However I realize this isn’t an answer to your specific question.
stevecym | 3 years and 8 months ago
Jh, I have spoken about something I made to drain standing water but I do not think it would suffice for real rain.
What stoopsitter mentions, a gravel bed (which is what these thing are the city is installing on some streets between the side walk and curb) and a drywell might do it.
So drywells are like the cesspools we had on long island. Cast concrete or block with holes in it for drainage. I watched my father put one in himself to remove the washing machine from the cesspool. I would say something like this, 5′ around, 6′ deep, surrounded by gravel, would help. But this is only a guess based on some thing I have seen decades ago. Someone inexperienced could get killed putting something like this in.
Here is why I am thinking it might be hard to find a contractor to make these: these were built by the cesspool companies and in an area that has had sewers for decades, there may not be many of these contractors.
If op does not find one, maybe look outside of the area.
andriywww1990 | 3 years and 8 months ago
and this is something i think works but again, i have no training and have really not read anything about these: if you make a drywell, the weight of the water above will disperse the water below out into the soil so as it fills, it will continue empty on the bottom. we have clay here so when i made the much narrower “drywell” i made, i was hoping that the weight would disperse the water below. that these might work that way can be confirmed i suppose by reading a little.
doorsby and stevecym are one and the same.
Arkady | 3 years and 8 months ago
You’d probably do better w/ a French drain or soak away.
chemosphere | 3 years and 8 months ago
I’ve seen people on this forum say something like “city code means your roof downspout on an attached house has to empty into your sewer, not your yard.” Is that true? Seems like the opposite of what some cities are recommending for big rain storms, where they have guides to rerouting a downspout to a yard.
dorkofwindsor | 3 years and 8 months ago
Imagine if everyone dumped their rain into the street or backyards…. thats a lot of water. .. based on my calculations just one side of a brownstone block, roof-only water for 50 houses would be 240,000 gallons. in a 7” storm like ida.
The city seems pretty relaxed about dry wells. in general. They are required on new builds where you can’t drain into a sewer, but require no notice, permit or inspection:
https://www1.nyc.gov/assets/buildings/pdf/drywell_installation_notice_insp.pdf
I believe 27-2027 is the code for requiring gutters to drain into the sewer. But we need to find a solution and push it on the city because this is not working.
Just to give a sense of scale, 7” of rain on a typical 20×50 roof is nearly 4,400 gallons. Much of that will go into the sewer, but the pounding of 3” in an hour is still a cool 1,870 gallons – not including your backyard drains…. yikes.
I do not know the percolation rate of my neighborhood, but it seems pretty hard clay a foot down. Park slope sits right on the last galacial terminal moraine and i do not know how effecti ve the drainage is at this level of water. So i’m assuming that its pretty slow. I am thinking a 1,000 gal dry well might be doable, i think something like a 5’ wide cylinder that is 6’ deep. Thats not small, and i have no idea how you get it into your backyard, but a typical 20×45 backyard (or whatever) could handle one of these puppies at the rear, and so could all on the block. So…. if you just use the dry well just for overflow / sump only maybe 1,000 gallon capacity is achievable. Hard to imagine, but storms could get worse….
I am brainstorming on another idea as my backyard is smaller than typical and i have a house abutting my rear; i do not want to put that much water near our foundations. I haven’t quite worked it through yet but it would be slightly higher maintenance than a set it and forget it dry well.
stevecym | 3 years and 8 months ago
Dork, the drywell my father installed was made of concrete blocks with rounded ends and a notch in them so the water could run out. They may have had a slight curve to them as well. They were no bigger than average concrete blocks, so they can be carried right through the house. They served the same roll as those big round cast cesspool things that we might still see in more rural areas.
So you have done all that math. How about telling us if the weight of a column of water will be enough to disperse water into the clay?
Great work, I have often wondered how much water lands on a roof.
dorkofwindsor | 3 years and 8 months ago
Hi Steve, here is a handy calculator for those Cliff Clavin moments:
https://water.usgs.gov/edu/activity-howmuchrain.html
I believe the rate of water dissipation into the soil is dependent on the so called permeability rate (which can be done with a perc test). So that can be tested for any given area but that is as far as my knowledge goes, there are DIY blogs for percolation tests but i have not done one, but i would assume would need to be depth appropriate. Brooklyn has such a diverse range of soil between till, outwash, wet, the terminal moraines, it would seem foolish to speculate how appropriate it might be for any given yard/ neighborhood. Basically I believe this is similar to testing done for a septic system. I doubt people do these for small dry wells but i’m not certain how effective those are when we are talking about giant storms, but at least those are getting the water far away from the house even if they are not adequate for that much rain.
Since I have not done this personally i feel like i am indeed treacherously close to Cliff Claven land. Bu t if my small yard could handle such a dry well i would probably start by calling a half dozen NJ and/or LI septic tank companies and see if i could get closer to something actionable.
stevecym | 3 years and 8 months ago
You won’t believe this, but I have a historic map of soil types for long island. Sounds like something you might appreciate. Probably bore a lot of people to tears. Are you a geologist?
colonialrevival | 3 years and 8 months ago
enjoying the pun, intended or not, at the insinuation of soil maps being “boring” ?
colonialrevival | 3 years and 8 months ago
enjoying the pun, intended or not, at the insinuation of soil maps being “boring” ?
JoeBushwick | 3 years and 8 months ago
My thinking is that I would need a dry well that could act as “shock absorber” when we get a huge downpour in a short time. My roof is about 25′ x 60′ so and inch of water would result in about 800 gallons of water in an hour. With a 1000 gallon dry-well, the first inch of rain goes into the well and anything over that goes into the sewer. If we get a sustained period of heavy rain, hopefully, the water in the well would slowly percolate into the surrounding soil. Probably need an engineer? to test the soil and design the dry well.