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rainwater catchment

Water harvesting

Posts: 114

Location: Southern Sierra Nevada's

posted 12 years ago

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We live on a property that has now city water and no well yet... Mollisons book has two drawings of harvesting contraption that throw off the first portion of a rain to get rid of the dirty roof water and then re-direct the cleaner water to your tank/cistern for drinking.
My question is, have any of you used one of these designs? How does it work? Do you recommend it or find that another design works better?
Also any thoughts on water quality for our consumption? That is to say have you suffered ill effects from drinking rain run off from your barn or house? Our composing toilet is not supper close and I'd hate to have a case of the "trots" at 3AM when its 10F. Outside and the wind is blowing.
Jim

CA, Southern Sierras, alt. 4550 feet, zone 9ish. (still figuring it out), 3 mo. grow season. Regular wind to 20 mph. SANDY soil with scrub oak,pine,and juniper. 2 seasonal creeks.

Travis Philp

gardener

Posts: 965

Location: ZONE 5a Lindsay Ontario Canada

posted 12 years ago

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What material is your roof made out of Jim?

http://www.greenshireecofarms.com
Zone 5a in Central Ontario, Canada

tel jetson

steward

Posts: 3701

Location: woodland, washington

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posted 12 years ago

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if you're concerned about water quality, slow sand filters are easy to build and very effective. haven't built one of the diverters, though I plan to.

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Jim Lea

Posts: 114

Location: Southern Sierra Nevada's

posted 12 years ago

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Travis,
Steel raised rib. Not asphalt.

CA, Southern Sierras, alt. 4550 feet, zone 9ish. (still figuring it out), 3 mo. grow season. Regular wind to 20 mph. SANDY soil with scrub oak,pine,and juniper. 2 seasonal creeks.

Jim Lea

Posts: 114

Location: Southern Sierra Nevada's

posted 12 years ago

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Tel,

Anything tricky to sand filters? Do you maybe have a good link? If it is effective it might take the mechanical out of the equation. I like that. Less to break... less to fix. If I'm thinking correctly the sand would build up with a type of algae. It filters? At some point it could be used in the circle of farm nutrients? Interesting.

Jim

CA, Southern Sierras, alt. 4550 feet, zone 9ish. (still figuring it out), 3 mo. grow season. Regular wind to 20 mph. SANDY soil with scrub oak,pine,and juniper. 2 seasonal creeks.

tel jetson

steward

Posts: 3701

Location: woodland, washington

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posted 12 years ago

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Jim Lea wrote:Anything tricky to sand filters? Do you maybe have a good link?Jim

nothing really tricky if they're put together right. one thing to keep in mind is that you've got to wait at least a week for the living part of the filter to really get going. the water coming out looks clean right away because of the mechanical filtration of the sand, but plenty of contaminants can make it through before the slime on top is active. and there needs to be a relatively constant flow through the thing to keep oxygen levels up. so if you're trying to supply all your water this way, you may want to have some bulk storage for the rain water that you can then trickle through the filter.

this page here seems decent. I believe I referenced that site when I built ours. took maybe half a day hauling five-gallon buckets of sand up a steep hill and washing it. maybe $10 or $20 in pipes and fixtures. I bought a 75-lb bag of small rocks for $5 since there aren't many on the property.

all of our household water is filtered this way. our biggest issues were iron and manganese, which the filter deals with quite well. I just have to remember to clean it out every three months or so, or I'm reminded by dry taps. when I finally get some rain catchment going, I imagine the cleaning interval will be much longer since the filter won't be dealing with copious iron from well water clogging things up.

I think the diverter is still a good idea for a roof, though, even with filtration. there will be all sorts of debris and contaminants on any roof that rain will wash off. a slow sand filter will remove that stuff without any trouble, but it will also need more frequent service if you're pouring a lot of crap into it. a green roof with living soil on top would take care of all this at once, but that's not a weekend undertaking like a diverter and sand filter are.

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Leila Rich

steward

Posts: 3999

Location: Wellington, New Zealand. Temperate, coastal, sandy, windy,

115

posted 12 years ago

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First-flush diverters are a very low-tech piece of kit. In NZ you can buy them cheaply. I'd make it the first part of a couple, or even a few filters. I've heard sand and solar filters are effective.
You most likely have significantly fewer birds and rodents than us in your climate, and no possums (note: no 'o'...), so the bacterial load from the roof will probably be relatively low.
I have a 'funny tummy' whenever I stay at this one place with no filtration and I attribute it to dodgy roof-water.
Jim, I might well have missed it, but what's your average rainfall and what season does it fall?

Jim Lea

Posts: 114

Location: Southern Sierra Nevada's

posted 12 years ago

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You guys have some great information. As for rainfall. 11.5 is Avg. This year so far 1. Inches that is.

CA, Southern Sierras, alt. 4550 feet, zone 9ish. (still figuring it out), 3 mo. grow season. Regular wind to 20 mph. SANDY soil with scrub oak,pine,and juniper. 2 seasonal creeks.

tel jetson

steward

Posts: 3701

Location: woodland, washington

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posted 12 years ago

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Jim Lea wrote:You guys have some great information. As for rainfall. 11.5 is Avg. This year so far 1. Inches that is.

what's the distribution over the year? how big is your roof? how much storage do you think you can manage?

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Jay Ritchie

Posts: 9

posted 12 years ago

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I haven't set up water catchment yet, it's on my to-do list. But I have painted many a metal roof in my day. Metal roofs don't generally look dirty from the ground, but once you're up there pressure washing the dirth and chalky paint off (which is usually the case when the roof needs to be painted), you realize how filthy they really are! I would suggest to anyone wanting to drink water off of their roof to probably wash it on an annual basis (don't fall off!) and to keep up on the paint job so that you don't have too much paint chalking off into your drinking water. That said, metal roofs last a lot longer than they used too.

Jay Ritchie

Posts: 9

posted 12 years ago

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And metal roofs around farms - especially animal farms - are the dirtiest. I've seen some considerable mold/mildew (I didn't get my mycroscope out or anything) on shed roofs out in the country, but it really depends on the place.

Amanda Bramble

Posts: 41

Location: Cerrillos, NM

posted 12 years ago

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We've been living off our rainwater for 6 years or so. Metal roof- not painted. I keep thinking of installing a first flush, but haven't gotten around to it. We don't have trees that drop leaves on the roof. But we do have bird droppings and dust. Depending on what system you use, the first flush should get installed somewhere where you will drain it regularly- freezing and breaking can be an issue if you live in a freezing climate. I have a screen between the downspout and the tank that I clean out as regularly as needed. We use a ceramic filter for drinking- make by British Berkefeld- The Big Berkey. It's red cross certified and portable- so it doesn't need to be plumbed into a system or have pressure. We love it. When we are waiting for the hot water to reach the tap, we always divert this cold water into the filter, so it's part of the system. We actually always brush our teeth with the straight rainwater and haven't had any problems.

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Jim Lea

Posts: 114

Location: Southern Sierra Nevada's

posted 12 years ago

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Tel,

Although the area is new to us as far as weather patterns go, we should get our rain in early spring. That said we at in a drought here in CA. I would imagine we should have about 4-6 inches right now and are at 1 or so.
Roof area is about a thousand feet of foot print. If I figure correctly an inch should get us 622 gallons? Our Avg rain fall loyally is 11.5 in. That puts us at 7153 gallons in an Avg year. We are trying to pick up our first 3000 gal. Tank now. Getting it in black or dark green.
I can't look back at your question on this phone once I start with a response... hopping I covered your questions.

Oh! This weekend we picked up an whole pallet of Frederick for .53 cents a piece! Woohoo! Rocket mass testing here we come!! This thing is starting to roll.
Thanks for all the helpeveryone,
Jim.

CA, Southern Sierras, alt. 4550 feet, zone 9ish. (still figuring it out), 3 mo. grow season. Regular wind to 20 mph. SANDY soil with scrub oak,pine,and juniper. 2 seasonal creeks.

tel jetson

steward

Posts: 3701

Location: woodland, washington

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posted 12 years ago

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that seems like a pretty good start. doesn't sound like you'll be able to get all your water off your roof unless you're very spartan, but certainly a good chunk of it.

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Jim Lea

Posts: 114

Location: Southern Sierra Nevada's

posted 12 years ago

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Yep, just a start. We'll more than double it when we get the pole barn built. Then add more storage capacity. Just having to take it one step at a time. Patience here is the key.

CA, Southern Sierras, alt. 4550 feet, zone 9ish. (still figuring it out), 3 mo. grow season. Regular wind to 20 mph. SANDY soil with scrub oak,pine,and juniper. 2 seasonal creeks.

Dave Tarsi

Posts: 1

Location: 40 miles north east of Seattle

posted 11 years ago

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We have been studying rain water harvesting / roof water harvesting here for 6 years. There are 3 rain water harvesting systems running here now that use water from a composition roof. We use slow sand water filters here. A biological sand water filter (often called a slow sand filter, or a biosand filter) will take nearly all of the petroleum pollutants (and 99.999 percent of pathogens) out of the water from a "tar" roof. Tar is actually used to seal reservoirs - it is basically insoluble in water below 50 degrees F. . These filters are totally sustainable. They don't need chemicals, or petrol or electricity to work. My websites have lots of info about these filters and much more along with over 50 scholarly references and documentation of over 60 epa certified tests showing how well these filters work. I just cannot believe that more people don't know about these filters. They use the naturally occurring life found in all water to form a biofilm in the top layers of sand contained inside filter. These microbes in the biofilm (usually called the "schmutzdecke"), actually eat the pathogens and break down petroleum residuals in water. I've thousands of hours of info on my websites. Its all free and licensed under the creative commons, and, sadly pretty much ignored by most people stateside. Check out slowsandfilter.org, roofwaterharvesing.org, and enlight-inc.com/blog/

Jim Lea

Posts: 114

Location: Southern Sierra Nevada's

posted 11 years ago

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Thanks Dave,
Will take a look.
Jim

CA, Southern Sierras, alt. 4550 feet, zone 9ish. (still figuring it out), 3 mo. grow season. Regular wind to 20 mph. SANDY soil with scrub oak,pine,and juniper. 2 seasonal creeks.

Mick Fisch

Posts: 672

Location: cache county idaho

102

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posted 11 years ago

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I would not hesitate to drink water off a roof, with the proviso that I would not collect rain for the first few minutes of a storm or shower.

Back in the '70's I lived in the Alaskan bush. My dad was in the FAA. The well water for the FAA housing was carbonated with sulpher dioxide or something and was ok for washing, etc. but was nasty for drinking or cooking. We were also told to not have open flames around our sink due to fire hazard. Anyway, the upshot was that everyone there got their drinking and cooking water from a rainbarrel.

We had aluminum roofs and each family kept a lid on their rain barrel. When it started raining we waited a couple of minutes for the water to wash the dirt, bird droppings or whatever else there was off the roof and then ran out and pulled the top off the plastic barrel and let it fill up. In the winter we pulled the barrel into the arctic entry and knocked off the big icecicles and put them into the barrel (we had hotroofs, so all the snow landing on the roof eventually turned to icecicles). The houses weren't very big and we had 8 people in the family but we never even came close to running out of water.

Rain water, particularly from a thunderstorm is superior for plants because it will have more nitrogen disolved in it (the ozone from the lightning forms it and the rain disolves it). I have a suspicion that even in a more polluted area, after a few minutes of rain, the air is washed pretty clean. Also, rain water is better tasting than any well water I've tried.

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