Rainwater harvesting systems in cold climates

[david j bockman]

Hi Philip,

May I ask about the first step in your proposed design, that being directing stormwater into vegetated areas before its collected? What are you hoping to filter?

Dave

[Phillip J Hutchinson]

David,
My thought is that the bioswale would filter sediment, contaminants and debris that may have collected on the rooftops between rain events. After doing a little more research, a first-flush bypass valve seems to address this and so it may only be necessary to direct that first-flush into a bioswale while allowing any stormwater runoff after that to go directly into the underground tank.

The general concept of filtering stormwater runoff is to ensure that any water leaving the site and entering the municipal system is cleaner than it would be if it just flowed from roof too sewer. The client will use the stored water for irrigation of both landscape plants and a vegetable/herb garden, and the water will be conveyed through a hand pump, so eliminating sediment, contaminants and debris is advantageous to this.

[Les Ballard]

“Grey” water should be filtered before it goes into the main tank and have a cistern to control overflow. Often, the filtered water is returned to the house – or now once again the garden – to flush toilets. It takes water like washing up water from the sink in the kitchen, into which pipe also flows dish and clothes washing water, filtering out of it food remains and dirt. That filtate is cleared from the filter either to the rubbish or, better still, onto a compost heap or into a similar system where bacteria break it down into new soil or fertilizer for the garden, Using chicken, pig and other poo in a 2 oil drum gas collector can power a domestic cooker and what is left behind is rich clean fertilizer so this can also be mixed with rotted filtrate. Even with care, stuff will get in the main tank and settle and so, every few years perhaps, a 10,000 gallon tank might be entered by an inspection haatch after venting and cleaned. The service can be found commercially from those folk also cleaning sceptic tanks. Sceptic tanks are a toxic envoronment whereas a grey water reservoir shouldn’t be toxic. In fact, it should not take much to convert the water back into drinking water or certainly for fresh clothes washing water, bath water, shower and even drinking. A secondary filtration system can be set up to facilitate this either in an emergency or for general supply. The reason for this is that, if you are prepared to pay for the filtration, you get better water than that which comes from the mains, has no added chemicals unless you add them and makes really nice tea! Also, people who buy bottled water need never buy it again. That kind of makes up for the extra filter costs.

At the end of your garden you can have a grey water shower heated by a yacht type wind turbine, hot tub, flush toilet, paddling pool for kids and fish pond with powered fountain and a muddy place for gardeners to clean up for very little. Most will want to pay for a foul drain yet the normal costs of such facilities will be offset with a green bonus.

Ordinary green facilities from foul drains in say a commune or hamlet, may consist of 3 ponds the last having water that could be drunk but you normally put this into a nearby river. The reed beds filter the water and it would be noted by the observant that most wildlife is not in that last one but eats muck from the first or second and widlife you eat – like duck and catfish – quite like the first one. Further information in this respect can be found under “Co-Operative Living” or “Sustainability”. The wind turbine I mentioned can be purchased or manufactured by the most ham fisted person able to buy a few parts and there are also solar panels, that can heat water for a hot tub, that can go on the pitched roof of the garden shed/shower/sauna or whatever. Every company should provide confirmation that specific circumstances / height / angle to the sun and their kit will do the required tasks on pain of making it right or giving a refund. While a large turbine may allow a school or several homes to save on electricity to the point of receiving funds from the electric company (where you put current into the system as well as take it out when everyone is draining at the same time) it is still very efficient to run a modern diesel in a box per 5 homes yet quite expensive to buy and maintain and replace batteries though these are now lighter and better than they used to be. A park HQ with public access to a display, classroom and toiles, ask nicely if folk will refrain from using the lift, if not disabled, as it drains their batteries a bit. That is now a decade old though. In respect of solar panels, photoelectric cells are now becoming more economical but the usual pumped water heating by the sun – on a dull day in winter even – exchanging heat with a system carrying hot water to a central heating and household hot water system – are very good but need say 30% of their cost extra reserving for maintenance over say 25 years and replacement may be necessary after maybe 35 years. It may not be suitable where a roof pitch does not, in the northern hemisphere, face south to south east.

I hope that a lot of the words, phrases and information given helps interested parties to cast their nets on the correct side of the boat when liasing with potential suppliers around them, on a forewarned is forearmed basis, yet it is only those suppliers who can throw the alternative technologies forward and they need patrons willing to accept limited advantages now to pay for greater ones to be developed and discovered. Affording water not likely to kill your teeth with too much fluoride, or bring on alzheimers with too much aluminium and other standard water treatments you do not need, may seem reward enough but, frankly, having some water for longer in these days of global warming will be the consideration in some areas. In Chicago, for example, you may think they have a lot of water. In fact, their pet lake is going to have a drop in water level over the coming 2 decades that would allow the city to be built again, dryshod, in the lake and dredging such sites to retain ports and waterfronts will not (always at least) be possible. Further, they may actually have colder winters with less snow but more rainstorms in summer. Their whole fresh water / drainage system will not cope with that and drainage solutions of the impact associated with London’s in the 19th Century following “The Great Stink” will be required. This means that new systems will be needed both on newbuilds and brownfield sites not connecting with the faiing systems or sewers. Clients will have to understand that this costs more than a bunch of so-called temporary fibre sewer pipes leading to existing sewers.

Luv n Lite,

Les Ballard

A lake like this Breton campsite one, but near me in South East England this year, had 20,000 pounds each in money 40 – 50lb carp, for fishing, with so little water the fish were getting sunburn, water had to be pumped out and back to oxygenate it to stop fish dying and water could not be taken to water crops (they being worth less than the fish). Other lakes also needed the attentions of the Fire Brigade. These are things a lot of unprimed folk would never consider.

[Phillip J Hutchinson]

An update on this project:
I have done a ton of research into rainwater harvesting systems, read several books (including Design for Water… which is a great resource) and talked to many different tank/infiltration system manufacturers.

We are more than likely going to use a modular catchment system (Aquablox, EcoRain, Atlantis D-raintank). This type of system can be much flatter and spread out than a typical poly tank, and won’t become an issue with a high water table. Also, since it is modular, the tank itself doesn’t have to be square. We plan to connect the downspouts to the tank, using a first flush divert and a sediment filter. The first flush will go into bioswales and then infiltrate back into the tank, and the sediment filter will make the tank essentially maintenance free (we are including a maintenance clean-out access on the tank just in case).

The tank itself will only be around 18″ in depth, and we’re planning on around 3′-0″ of soil cover with plantings on top of that. (Probably around 18″ of planting mix, then a layer of granular to allow infiltration, separated by fabric)

It’s been an interesting experience learning about the different systems and issues affecting rainwater harvesting. Thanks for all the comments and suggestions here, they were quite helpful. I’ll post another update when the design is finalized, and possibly a few installation photos this summer when the system is being installed.

[Author]

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