Rainwater harvesting systems in cold climates

[Phillip J Hutchinson]

Does anyone have experience designing/building rainwater harvesting system in a northern climate (Chicago)?

I would like to design a system that directs runoff from roofs and walkways into planted areas as a means to filter the runoff, then capture it and store it in an underground tank for re-use as irrigation. The project site is very small, so burying the tank underground allows us to save space. I need specifics on how a system like this might be designed and constructed, what kind of materials might be used, methods of conveying water from roofs to an underground tank, etc.

What happens to the system in the winter and what kind of effect does freeze/thaw have on a buried storage tank and associated plumbing? How is water typically conveyed from roofs/site into a planted area and then into a buried tank? What happens if we get a big rain event and the tank is full?

Thanks in advance to anyone who can help.

[Dominic Esser]

Hey Phillip,
I think rainwater harvesting systems are a fantastic idea, in fact, depending on where you live (like me where the average annual rainfall is low) I believe harvesting greywater for irrigation is a great concept as well. Personally I have only seen an above ground rain harvester, very primitive, where the water spouts from the roof run into a huge barrel and then the garden was manually watered from the barrel. I believe you could use the same idea underground. Being that this project is in Chicago, I would say putting the collection tank below the frost line and insulating it to deter the water from freezing and having a emergency runoff (kind of like you see in your sink, where the water goes into that little hole once the sink gets too full) I dont know too much about this, but thats just what I think. Check out this site http://en.wikipedia.org/wiki/Rainwater_harvesting

Dominic

[Miles Barnard]

Phillip this is a really good website with lots of good resources.
http://www.harvesth2o.com/

I also have a book called ‘Design For Water’ by Heather Kinkade-Levario. It’s full of technical information, photos and diagrams of actual systems. A cistern in a cold climate like where I live (Maryland) should be thought about like a septic tank. Frost line here is 24″-30″ and there are plenty of tanks where the lid is not even that deep and we never have a freezing issue. So check out these resources and post your pictures when you get a system built someplace.

-Miles

[Phillip J Hutchinson]

Thanks for the resources guys.
The tank I’m designing needs to hold 850-1000 gallons, and I’m thinking it’ll probably polyethylene though it could possibly be built out of concrete. I’m assuming I’ll have to bury it so the top is 42″ below grade to avoid any freeze/thaw issues in Chicago.

My plan is to have the roof drains discharge into planted bioswale areas, allowing the water to infiltrate through that medium and into a perforated drain tile underneath that then discharges into the underground cistern. Above grade there would be a smaller decorative cistern with a hand pump that can be filled with water from the underground storage tank so the homeowner can do some hand irrigation when needed. The underground tank will have an overflow connection to the public sewer system, and also a slow and controlled discharge into the sewer that empties 3/4 of the tank over a period of time so it acts as detention during storm events. (I’m assuming that the homeowner isn’t going to need 850 gallons for watering plants between rains, so ultimately that water has to go back into the sewer system but it’ll be cleaner and not add to the volume during storms).

A few more specific questions:
Is there a concern about the integrity of the underground tank if it is completely empty?
What kind of maintenance access do I need for the tank? (i.e. man hole, or a hand sized hole?)
Is there any need to design a system that allows for a “first flush” to go directly into the stormwater sewer, to avoid lots of contaminants/debris/pollutants?
What can be on top of the buried tank? Walkways and planting? (It’s in a back yard, so there won’t be vehicular loads)

[Mike G]

For any residential project, for constructing and maintaining, keep it simple. I’ve personally had to clean out large tanks before and its much easier if you’re able to get a ladder in the opening and crawl through. I would also think a direct line from your downspouts directly to the tanks, coupled with a first flush bypass type valve, would be the way to go. After the first flush drains away the water should be plenty clean for irrigation. Your flush and tank overflow could drain into a bioswale to keep more water on site if you’re trying to keep the water onsite. As far as your tank specs go, the manufactor should be able to supply you with that info.
Sounds like you’ve got an interesting project. I also recommend ‘design for water’ as Miles mentioned. Good luck. – Mike

[Bob Walsh]

Rainwater Harvesting – Studies reveal that as much as 60 percent of a homes water use doesn’t need the stringent treatment undergone by most water treatment facilities. Rainwater harvesting provides a great alternative source of water you can use for these tasks: things like laundry, irrigation, and washing the car, potentially reducing your use of city water (and thereby, your water bill) by up to 60%. This can reduce both the amount of water needed to maintain a healthy lawn, but also the amount of fertilizer and pesticides needed, saving you money on your water bill AND reducing the harmful impact of those chemicals reaching the environment via run-off.
Greentech are specialists in a range of Rainwater-Harvesting Services.
http://www.techstore.ie/Renewable-Energy/Rainwater-Harvesting.html

[Miles Barnard]

Phillip I’m going to play devil’s advocate here. Are you going to be setting up a pump inside the cistern and using the water for a real irrigation system? Or will you just have the hand pump for hand watering? Unless you are either drinking the water or using it for an automatic irrigation system the whole rainwater harvesting into a cistern might be overkill. If it’s all coming off the roof I don’t think I would then send it back through the ground for filtration. I think you will loose a lot of the water when you send it though the birretention area (the idea is to harvest the rainwater, right?) and the water coming off the roof after the first flush should be pretty clean. I’m no expert, just surmising here. If you send the water through bioretention you definitely do not need a first flush device. If going directly to the cistern yes you do need first flush. If the tank is rated for burial you should not have a concern about structural issues but you need to check with manufacturer. Yes you will probably need to have the option of putting a person into the tank for potential maintenance. Depending on how the tank is rated for loads you should be able to put anything you want over the tank. And unless Chicago has a combined Stormwater/sewer system you might have issues connecting you stormwater management stuff to the sewer. I would encourage you to get that book I mentioned. Go United!

[Phillip J Hutchinson]

Good thoughts Miles, and I appreciate the counterpoints. I think the main goal (aside from checking the LEED boxes for water-reuse) of the system is to provide non-potable water for use in gardening as well as reducing the burden on the municipal stormwater system. We may use automated irrigation for part of the landscaping, so I’d like to at least explore that possibility.

As Mike mentioned below, a first flush bypass into a bioswale, and then a direct connection from rooftop to the cistern sounds like it would be adequate for filtration. Directing all of the runoff into bioswales probably isn’t necessary, and may actually create drainage concerns during big storms.

I will look for the book, or order it online. Sounds like it’ll answer a lot of my questions.

Thanks!

[Miles Barnard]

Re: Bob’s comments. Down in the virgin island where ALL domestic water is what falls from the sky they catch it on the roof, run it inot a tank and drink it. Period. Sometime there is a simple cartridge filter in the mix. I know they don’t have the air pollution issues we do, but It makes you think about how simple this really all could/should be.

[John Bauer]

Phillip – We are a company that specializes in rainwater and greywater harvesting systems – located in the Chicago area. We invite you to visit our website for a lot of information on options for rainwater and greywater harvesting – http://www.Wahaso.com.

In particular, we like a tank system that is very flexible in the design layout for width, depth and capacity and quite suitable for home cisterns (Atlantis D-Raintank). The tank is assembled on-site and wrapped in a permeable geotextile in an excavation lined with an impermeable liner. The tanks are made from recycled polypropylene and not susceptible to frost below grade. They are perfect below a swale that can collect large quantities of stormwater or rainwater that can then filter into the top of the tank.

[Les Ballard]

try googling grey water systems for homes

to answer your question. you filter the runoff includng bath water, etc. into the tank which overflows via a cistern to the sewer and in some circumstances you may also need to flush filters. You then irrigate via the tank to the garden and it is possible to do that via a yacht style wind motor and.or solar power. A panel can also be used to warm the water in some applications but it is a case of putting together the system through the good offices of the main supplier. It is appropriate to allow use of the tank as a fire reservoir and return filtered water to the home to flush toilets and more. Sorry for where I am wrong according to parties you contact but this will give you a clue as to how much hose and kit you need for a full system and what different folk are likely to tell you. Hard tanks may have a hatch so you can get inside to fix or clean them some years.

Please consider local seismic and water table levels when planning burying tanks and how deep you do it.

Luv n Lite

Les Ballard

[Warren Gorowitz]

I would also suggest looking at the Aquascape Rain X Change product. There’s quite a few systems installed in the Chicagoland area too. http://www.rainxchange.com

[Andrew Garulay, RLA]

The project that I was involved with used a typical gravity roof drainage system with pvc piping going into a brand new 10,000 gallon (yea, it was a big one) septic tank.There was no need to filter the water through a bioswale because that was going to happen when it was sprayed as irrigation. The septic tank was to have a centrifugal pump in it. It was buried deep enough not to freeze and had an outfall pipe just like any septic tank for if and when the tank became full. That water went to a bioswale to infiltrate into the ground for replenishment and purification.. I did design a cleanout at each downspout that used 8″ pvc vertically so that there was a place for debris such as twigs or small branches to fall out and a sump for any sediment that could be opened and cleaned out.

I do not know if the system has been utilized yet.I switched jobs before it was complete. The piping and tank were in, but the pump system had not been set up. It was a historic restoration of a nineteenth century estate being funded by donations. They spent 6 million on the building, so the budget was slowing down the completion of the landscape. I really need to follow up on this.

Simplicity is the answer as someone else pointed out earlier.

here is a link to a photo of it going in: http://picasaweb.google.com/highfieldhall/HighfieldHallRestoration#5224349391871201266

[Dominic Esser]

Wow, that project came together really nicely. That is a beautiful house and property. Must have been fun and also frustrating working on this project.

[Andrew Garulay, RLA]

It was fun and quite an experience dealing with many, many, groups with individual agendas. My portion of the job was not the overall landscape. I recommended that they find a Period LA which they did. I was responsible for parking and pedestrian circulation.

Interestingly, there were two brick cisterns found underground for water storage, quite possibly done when the house was built. These were almost certainly to store roof runoff. I’m not sure if the water was used to irrigate the cut flower garden and greenhouse that was over the edge of a cut bank quite near the house or for what I believe is the ruins of a fountain in a sunken garden on the other side of the house. The plan was to use at least one of those as well as the 10k tank. We also had plans for a second 10k tank under the parking (that did not happen as the budget was depleted and the parking was essential to generate income).

The parking was the most challeging political issue with the entire project. Aside from the various factions within the restoration group, there was the tree warden, the historic commission, selectmen, and others that had to approve it. There were 9 completely different parking concepts developed. I actually represented them at two major hearings after leaving the company because I had so much time and effort invested in it that I had to see it through.

The most satisfying part for me was that I was able to find a better solution for ADA access on the front entry than to have a similar ramp to that on the rear of the building that the architect’ had designed for the front. I had them make a masonry foundation to the porch and made the grading of the walkway stay below 5% and still have 2% positive surface drainage all along the house – one of those un-noticed things that have a huge impact on the outcome of a project..

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