The Sustainability Review:
Rainwater Collection

This is my story regarding our water system. My family and I decided to sell our house and move to a piece of land below the summit of Moscow Mt. at about 3100’ elevation. I’ve always been a careful consumer of water and want to tread lightly on this precious resource, so it was only natural to look towards rainwater as a source. Besides, our well was a low producer, 0.15 gpm (a dry well by most people’s standards).

I had seen various rainwater systems over the years and have a friend who is in a similar position to ours not too far from here. I studied his system, put in many hours of research on the computer and books, and talked to various folks in the industry. Last summer I built the system in hopes of capturing the rain/snow from the winter approaching.

One of the main components of a rainwater system is storage. Ideally storage is underground where freezing temperatures aren’t a concern but with the frequency of rock I ruled out digging and placing tanks in the ground. There was a rather odd structure on the land when we purchased it, a long, barn board sided, oddly framed post/beam structure with a nearly flat roof about 100’ long and 30’ wide. I framed in a room and insulated it just large enough to hold the 4 tanks I would need to hold a good supply of rainwater. Each of the tanks is 1600 gallons making a total storage capacity of 6400 gallons (only about 6000 is actually useable due to plumbing).

Once the tanks were in place I set out to put gutters up and install the plumbing to tie everything together. Many people add a “roof washer” that diverts the first rain off the roof so you aren’t collecting dust/leaves/bird droppings/etc. At this point I haven’t installed one since but I’m working on a design that is low maintenance and effective. I do have a coarse gutter filter that keeps large items out including mice.

The tanks are connected together at their bottoms by a 2” manifold that allows them to fill evenly. My friend’s system has shown that the vast majority of sediment and algae formation occurs in the 1st tank leaving the remaining 3 tanks clear. I plan on getting a swimming pool cleaner that will allow me to suck the sediment from the 1st tank when it builds up. I installed an overflow that is simply a 3” pipe that I glued into the top of the tank at the level I didn’t want the tanks to exceed.

On 2/1/06 I started filling the tanks. On 2/13 they were all at 1000 gallons and on 3/20 they were all full. I have 2 more roofs to hook up still and can’t even imagine the quantity then. We have been living here since June and as of today, 7/20, we have 5800 gallons in the tanks.

As for filtration of the water we have an under sink filter that filters out nearly every undesirable of concern (Eternity made by Seagull Distributing, $410). I am really hoping that we can fulfill our needs with rainwater entirely. We plan on having a large garden and fruit trees, which I know will be the largest water demand we have. I think additional storage is going to be needed but fortunately it can live outside since it’s only needed in the non-freezing times of year.

If my story sparks your interest I would love to share my spreadsheets for analyzing your water consumption, estimated flows off your roof, and my schematics of the plumbing system. I think this is a very viable option for our area. 

On a final note, unlike much of the water in Moscow, rainwater isn’t hard, doesn’t have high iron and tastes fantastic….

Letter to the Editor
By Michael Robison, EcoWater Treatment Consultant, from the September 2006 Newsletter

I very much enjoyed reading “The Sustainability Review: Rainwater Collection” article in the August issue. Mike Forbes’ water storage project and his plans for the future are great! I look forward to creating a similar system one day myself.

There are two aspects of Mike's article that I am called to respond to:

1) Mike uses the Eternity System water treatment product made by Seagull Distribution. As a water treatment consultant, I am always interested in "new" water treatment products. The Seagull line of products is new to me. The information offered on the Seagull website is generally of interest and value, although I did find some less-than-acceptable information. I give them a "thumbs up" for for the quality of their products. After speaking with one of their representatives, I have to add that the Eternity System is a very expensive, and very simple, carbon filtration system. I imagine the housing will last virtually forever. However, the filter cartridge is nothing more than a carbon filter, with the same level of effectiveness and limitations of most carbon filters. Its effectiveness does not compare with the effectiveness of a reverse osmosis system.

The other aspect of Mike's system, and the main reason I am writing "to the Editor" today, is the bacteria and other contaminants a rainwater system is likely to collect.

In my educated opinion, the Eternity type of carbon filtration is intended for use on municipal and private water systems (chlorinated systems) ... and not well suited for a rainwater collection system, unless it is supported by a series of sediment and carbon prefilters and an ultra violet light. Water tanks, cisterns and water collection systems are notorious for breeding bacteria. Was I drinking or cooking with water from a rainwater system, I would consider sediment and carbon filters, followed by a UV light to be the minimum level of protection.

When drinking/cooking water is stored in a tank of any kind, a cistern, spring or even a shallow well, I encourage folks to have it tested for bacteria at least once each year ... and if bacteria is found, to take the appropriate action ... at the very least, not drink it. Please keep in mind that bacteria is but one of the many potential water contaminants. I encourage every private well owner to have the full private well analysis performed at least once every two years.

I am looking forward to hearing more from Mike as his rainwater collection system continues to evolve. I understand a UV light is part of his future plans. 

The Sustainability Review — Rainwater Collection, Part 2

Last month, I wrote about our rainwater system. I had some feedback regarding some of my ideas and the system itself. There is an article to the editor this month that addresses some of what I said last month. I thought I should address some of the issues brought up by Michael Robison in his letter this month. He makes some excellent points, and has made me look very carefully at my system and methods by which I treat and plan on treating my water. I am also looking into options I hadn’t previously thought about.

Let’s start with where the water falls. Most rainwater systems have a “roof washer” for flushing the initial rain. This is for cleaning the big stuff off so you don’t have to filter it later on. I don’t have one because I’m trying to design a system that is low maintenance, effective, inexpensive and operates well in freezing temperatures. To my knowledge, a roof washer like this doesn’t exist. Fortunately, my collection roof has very little on it other than dust (i.e. no needles and very few bird droppings). I do have a coarse filter to keep the stray needle and small critter/bugs out of the collection pipe.

After the water is funneled into the pipe, I intend on having a water sensor that activates a germicidal UV filter that kills all bacteria as they come into the tank. This isn’t enough of a system to deal with bacteria because they can form in the tank and filters. It is purely an additional method for eliminating some of the bacteria present in the system. UV filters have the problem that they don’t work well with turbid water and they do draw power while in use. I haven’t tested the turbidity of the water coming into the tank, but will do so when the rains come. The UV light I plan on using only uses 8 watts of power while running, and since it’s actuated via a sensor, it won’t operate continuously like many do.

Once in storage, the greatest potential for bacterial growth happens. Typically, people dose their storage tanks with chlorine bleach. I’m opposed to drinking a poison, so this isn’t an option for me. There are alternatives, and if you look to New Zealand, where rainwater systems are very common, it is typical to see people treat their water with hydrogen peroxide (H202). They don’t use the household variety, however, but 35% technical grade H202. H202 is a very effective germicidal agent, leaving only oxygen in the water once it’s done its job. I’m still researching this, but my research has shown that it should be very effective.

We have water now that is pretty good (I’ll actually test it once a year still) prior to any filtration at the point of use. Most of our water will not be ingested (irrigation, toilet, shower, hot tub) so filtering every bit isn’t absolutely necessary. Filtering can best be done by reverse osmosis, however, I have a difficult time with wasting 25-50% of the water you get out in the end. I’d rather opt for a carbon block filter, even though they have their issues. As Michael points out in his article, the carbon block filter can be a source of breeding bacteria and may not filter as well as the supplier claims. From what I’ve been able to determine, the carbon block filter I have (Eternity by Seagull Distribution) is effective in filtering bacteria. There are many forms of carbon block filters out there that are probably cheaper than mine that perform as well (EcoWater has excellent filters).  Speak with the salesperson about the performance of the filter with regards to bacteria filtration before buying it, and have your water tested at least yearly to see if anything is passing through the filter that you don’t want to drink.

At this point in the system, I think the water is clean enough to drink and should keep you healthy and happy for years to come (as long as you maintain it as well).

Mike Forbes is looking forward to this winter, sitting in his rainwater-supplied hot tub heated by the sun and wood.

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