To start with we looked at the typical water usage of a home. We found that nearly 70% of the water used in a home is for landscaping, outside hose bibs and toilets. So, if we could find a way to cover a huge portion of the water usage at a fraction of the cost of what's available on the market we could help people into sustainability.
We came up with a system that includes a 1,700 gallon underground collection tank and a Master Shield gutter system that filters the rainwater. During a rain the first 10 gallons of water are collected and drained off to remove the huge majority of "undesirables" which is required by code. The rest of the water is collected in the tank. We are introducing a small amount of city water into the tank for the treatment properties it offers. 
Water can then be pumped out of the tank on demand using a 15 gpm pump located outside the house. If the tank is drained to less than 250 gallons a valve in the crawl space switches the toilets, hose bibs and sprinklers over to city water. During a pump failure or a power outage the system will also switch over to city water. Our home monitoring system will show how much water is in the tank and differentiate water usage between collected rainwater and city water. By knowing how much water is being used and how much is available in the tank, homeowners can make small changes to reduce their overall consumption. We will be installing two stage toilets that have the option of a .8 gallon "half" flush or a 1.6 gallon "full" flush which will also help manage water usage.
Our aim is to accomplish all of this for under $8,000. By making the decision to help reduce city water usage by 70% rather than 100% we can offer a savings of $22,000 and we can make it available to many more people.
The overall result of 100 people reducing city water usage by 70% has a much greater positive impact on the environment than 1 person reducing city water usage by 100%. And currently, the number of people choosing a $30,000 system over relying on city water is nowhere near the 1% in that example.
Posts
Very nice work, especially with incorporating the automatic switching to city water. I am curious as to where this system is located to get a better idea of the average rainfall at this location. As you are surely aware, the main expense for a rainwater collection system is the storage tank which must be sized appropriate to the catchment area and the rainfall patterns. Residents in locales with frequent and abundant rainfall will require less storage than those in more arid areas or where rainfall is concentrated to only a few months of the year.
ReplyDeleteThrough research,I have found that the average indoor water use (excluding irrigation) is around 10,000 gallons per month for a family of 2-4 people. Therefore, to replace 70% of a home's water needs with rainwater, approx. 7,000 gallons per month would need to be supplied by the rainwater system. In areas where it rains frequently (every other day), this may be possible with a tank that holds less than 2,000 gallons. However, in most places, it is not uncommon to have dry spells of 3,4 or 5 weeks on end.
A rule of thumb, is to have 3x the amount of storage as you will require each month in water usage so that the system can collect and store water during heavy rain events and still provide water during drought events. For the average home this is a tank of 20,000 gallons or more, unless of course rainfall is frequent and predictable. As the author of the blog states, many systems sized to provide 100% of the home's water needs cost around $30,000 simply because of the large storage requirements.
I agree that the long-term and economically feasible alternative is to use smaller tanks that reduce the amount of water required from the municipal system and reduce the homeowner's investment significantly. Good work!
Wow, when I first read $30,000 for the system I was going to ask where you got your system as you were majorly ripped off.
ReplyDeleteYou definitely went with more economical system.
Is that a Leader pump? How has it handled its duties thus far. Their pumps have been on my Wish List a while now and it looks like you went with the same set-up I was envisioning.
Did you get everything from one place? Which one? I've narrowed down the field to raintankdepot.com but would love some insight from others.
Good luck!
Black Bear Explorer,
ReplyDeleteThank you for your comments. You have obviously done your research.
We are located in Portland, Oregon. So, we do have substantial rainfall for the majority of the year. Because of that, collection is less of an issue.
According to the Portland Water Bureau, the average residential household in Portland uses 7CCF per month. That converts to 5,236 gallons per month, per household. Now, keep in mind, that’s the average so it includes all of the older higher usage toilets, inefficient shower heads and higher usage washing machines. Considering that, we think 7CCF is a little high for new houses that have more water saving features required as part of the building code. But, let’s look at 7CCF in our house. If we’re trying to cover 70% of that, we’re looking at 3,665 gallons per month. If we can also do some things that make our use of the collected water lower than average we can reduce the 3,665 gallons even further. By installing, dual flush toilets, a water monitoring system and using native plants in landscaping we have forecasted that we can cut collected rainwater usage by 20% to about 2,900 gallons per month. Granted, there will be one or two months during the summer where we may not be able to collect all 2,900 gallons and the need will have to be covered by municipal water supply.
For areas with less frequent rainfall we can install larger tanks but what we’re really focusing on is trying to make it easier (more affordable) for more people to have less of an impact on the environment. That’s what this house is about. We will find out exactly what the right size tank is. Averages and projections are great but there’s nothing like a real world application to prove it.
Thank you again for your comments. We always welcome them.
Most of the costs associated with a $30,000 system are for excavating for the huge storage tanks and for the purification systems that are needed when a system replaces ALL of the municipal water. That's why we chose to go with a smaller storage tank and use it only for water that does not need to be treated for consumption.
ReplyDeleteThe pump is a Leader Ecojet 110 we purchased through Mastershield. We're still in the process of installing the system so we haven't had it put to the real world test yet. Keep checking back here as we'll be reporting on all of the products we've used.
MirandaHomes has brought to attention a very important and necessary fact regarding rainwater harvesting- to make sense, it must be coupled with water conservation.
ReplyDeleteTo anyone thinking of implementing rainwater harvesting into their home or business, I would recommend that you first find ways to reduce the amount of water that you use and then size a rainwater system according to this lesser amount, as Miranda Homes has done. There are many ways to go about this, most of which are not incredibly expensive, and by reducing your total demand you will recuperate the cost of these water conservation measures by choosing a less expensive rainwater collection system.
When homeowners approach our business and are curious about rainwater systems, we first ask them how much water they use. Not surprisingly, many of them have no idea how much water they use. Often they will know about how much their water bill costs, but rarely how many gallons per month they are consuming. In our area (North Texas), it is not uncommon for residents to use 100,000 gallons per month (yes, per month) on landscape irrigation and such a large number does not translate well in most people's minds. In order for it to make sense, I tell them something along the lines of "well, if you filled your entire house with water- that's about how much water you use each month during the summer to keep your landscape green." In instances like this, rainwater harvesting could only possibly reduce your total water consumption by 5%, based on your average rainfall so it doesn't make much sense. HOWEVER, if you would consider switching to an appropriate landscape, using native plants, it is possible to account for all or most of you water needs through rainwater harvesting.
My point is- rainwater collection makes the most sense for people who have a grasp on how much water they use and are FIRST willing to take steps to reduce this demand.
Thanks for the post, MirandaHomes.