23 January 2008

Rain Harvester Part 4 of 4

Every part of our rain harvester works on nothing more than gravity. It is a system that utilizes ten steel barrels; nine hold water and one creates the pressure that fills those nine barrels. I’ll break down the whole shebang into two parts (each with its own subsequent parts): first I will go through the process of filling and second I will go over, yep you got it, how it drains.

The Big Fill

The amount of roof space we’re using is only about 360 square feet. We have access to more, but haven’t gotten around to running the necessary downspouts. Obviously the roof is what collects the water, so the more that is utilized, the less rain that will be needed to fill the barrels or the more barrels that can be reasonably filled. We have one downspout that empties into what we call the lead or filler barrel. Because a roof can collect a lot debris that eventually washes off when it rains, it is always a good idea to include some kind of filter. Our filter is quite simple, it’s a piece of chicken wire and window screen fastened over the top of the filler barrel with some wire.

As you can see, the filler barrel is propped above the other barrels on a tall wooden tower. The reason for the rise in elevation is to create added downward pressure in order fill (hence “filler” barrel) the storage barrels. The added pressure is required because the water fills the from the bottom up. The reason the barrels fill from the bottom is because that is also from where they drain (Ahh, gravity).

The draining part of the equation works fantastically. The filling part, hmm, well let’s just say it manages to do the job. If neither Meg nor I have mentioned this yet, the harvester was designed with a fair mixture of solid math and good faith. I am learning at an early age that good faith can leave you with your pants around your ankles. The filler works great anytime that there is a good slow and steady rain or less, but if there is a thick and heavy downpour, then the pressure isn’t strong enough to keep up and we end up losing water from the tom of the first storage barrel. To combat this we may run an overflow line to the end barrel to even things out.

By the way, the reason we didn’t top-feed the storage barrels is because we wanted to avoid running two whole sets of pipe (top and bottom) when we weren’t even sure how well it was going to work. The line running along the bottom of the barrels has to be there in order to drain properly. Also, if you build a closed-top system like ours, which means you can't get into the barrels, be sure to drill a small hole into the top to relieve any counterproductive air pressure and promote easy filling and draining.


When all of the storage barrels are full we have 500 gallons of water trying to rush down and out of a straight line of ½ inch PVC, which is about 8 inches off the ground. The simple pressure from the barrels alone produces a steady stream of water, but the additional downward grade of about five feet to the garden give us all the water pressure we need.

It’s important that the drainage line connecting all your barrels runs in a straight line. Just like the gutters and downspouts on your house, any directional changes will lower the water's pressure and velocity. Think of it this way, if you're riding your bike down a steep hill and there is a turn up ahead, what must you do? Oh yeah, slow down or die.

It's handy if the spigot has a splitter. A splitter allows you have one hose running to the garden and a second to fill watering cans, put out fires, rescue small sea creatures, and any other good deed outside of the garden.

If you have a pond that is relatively close and downhill from your house or barn, you can build this system with a thicker drainpipe and run an old fire hose to fill it up. We are going to do something like this for our pool. When it rains, we’ll just open the rain harvester drain and let it all run in.


Taking care of this thing is pretty simple. Always make sure that the gutters on the roof are clear for maximum drainage into the leader barrel. If you find any openings in your system where major debris can get in, it is to your benefit to cover them. Any junk that gets into a closed system is not coming out and can really plug things up. Another way to avoid this is to get barrels without tops and cover them all with screens to keep bugs from breeding. Other than that, the only thing you would need to do is drain it out completely in the winter; if you live in an area where it freezes you know why.

Links to this series: Part 1, Part 2, Part 3

If you have any suggestions or would like to link your own rain harvesting system, please feel free to do so in the comment section of this post.

Kelly and Meg


Patrick said...

I've really enjoyed reading these posts, thanks for making them. I think this is the kind of post series that will stay in search engines for many years and people will continue to find it and read it.

I have one more comment to make. You used PVC pipes, and other people considering a system like this may want to use something more environmentally friendly. PVC is one of the last few widely used plastics that contain chlorine (this is the C in the name), and like most chlorine based manufactured compounds it's very long lived.

CFCs that destroy the ozone layer are another good example of long lived chlorine compounds. Some banned pesticides like DDT are other examples.

It's over these compounds that you sometimes hear about Greenpeace blocking shipments of chlorine.

Household chlorine (bleach) is something completely different, and in fact is very safe. It's only when chlorine is combined with other elements in manufacturing that it is a problem.

You already mentioned this was a short term setup, on a rental property and so on. Once you are done with your PVC pipes, and throw them away, they will sit for a very, very long time in the landfill. Most other plastics like PE plastic shopping bags will break down in decades or maybe centuries, but PVC will be around a lot longer. PVC is also difficult to recycle, and if it is burned or heated to a high temperature will decompose into PCBs which are very toxic and also very long lived.

PVC has lots of uses in the garden, like plastic coated fences or garden tools, and I certainly use it sometimes. It does after all stand up to sunlight and last forever, which is what we want sometimes. For temporary constructions however, it's better to use a plastic or other material with a shorter life or that's easier to recycle.

Maybe I need to do a post about this...

Kelly said...

Hello Patrick, Thanks for the comment. I was wondering, are there any environmental negatives involved in the production of PVC? I ask because I have to admit that I love the stuff. It can be adapted to serve so many purposes. I would be most interested if you would do a post about it.

As far as what will happen to the PVC from our harvester, I would like to defend Meg and myself and assure you that we are strict re-users. We throw nothing away if it can serve a new purpose. The short term part of the harvester is actually the barrels. They're steel and will eventually rust through. Thankfully steel is a recyclable material and we can properly dispose of the bombed shells when the time comes. We do hope that the rest of the system will out last our living here and future tenants can switch to plastic barrels as the steel ones die. Either way, thank you for bringing it into the conversation.

peter hoh said...

Came to your blog through a post on GardenRant. I've enjoyed poking through your archives. Wish I had a couple acres in southeastern PA to plant and play with. We moved from the Lehigh Valley to the Twin Cities a dozen years ago. Now I've got a city lot in frigid Zone 4. At least I'm on a corner.

Meg said...

Hi, Peter. I'm originally from the Lehigh Valley--from Bath, just north of Bethlehem. I've never been to St. Paul, though Kelly and I were at a conference in Minneapolis a couple years ago and we loved the city. Even though it was just October when we were there, it was already pretty darn cold. I just checked out your blog--it's great. You've got one hardcore compost bin! Thanks for stopping by.

peter hoh said...

I know Bath. If I recall correctly, we used to get milk -- in glass bottles -- from a dairy south south of Bath. I used to go to a lot of auctions in that area north of 22, from Northampton to Bangor. Googling leads me to Wil Hahn's site. I think he was the auctioneer I used to follow around.

Glad you like my old compost bin. It's about 10 years old. Wish I had the room (and the chickens) to do onw like yours, but I have to keep it compact and tall in order to fit in my garden.

Anonymous said...

Looks fantastic, would be wicked to have the space to do that.

On the subject of 'The Growing Challenge,' i thought about it, then decided not to as i don't think i can blog on 'mange-tout' every week! Good luck with yours though, what will it be?

Twinville said...

We're enjoying your Blog from the mountains of New Mexico, especially your posts on rain harvesting which we plan to to do this summer. As you probably know water is precious in the Southwest and we'd like to save and recycle as much of it as we can...especially the free stuff.

Your explanations of how you built and planned your own harvester are very helpful.

Thank you!
Laughing Orca Ranch

Meg said...

Peter, that's pretty cool! Though that dairy is most likely an enormous subdivision now. blech.

Vegmonkey, I had to go to a British-to-American dictionary to look that up. Pathetic! And now that I know what you're talking about, I agree it could get dull.

We're also doing peas--capucijners--but in addition we'll have a couple new varieties of potatoes and tomatoes, and celery from seed, and maybe beets, so we'll be able to keep a bit of variety to our posts.

Twinville, we're glad you found it helpful! We recently watched a movie called "Building with Awareness" about a guy who built a straw bale house in the southwest--I think it was New Mexico--and he included a giant cistern for gray water collection and reuse. Something like that would be a definite plus in your locale!

Meg's mom said...

Meg, what is 'mange-tout'?

Peter, that dairy was a big pool store but now is just empty.

peter hoh said...

Thats too bad about the dairy. I'm sure it would just break my heart to see sprawl along those lovely Lehigh Valley backroads I used to wander.

Patrick said...

Meg's Mom:

Mangetout is French for 'eat it all up'. In British English instead of saying snow pea or sugar pea, they call them mangetout peas.

Anonymous said...

You know, i feel like we are educating the nation Meg, with our anglo-American cross country mange-tout defnition project. Ironically the variety is called 'Oregon Sugar Pod' - how ironic!

Meg said...

You know, Kelly and I were really perplexed when you finished off a post of yours last week by saying you had to "put the tatties out to chit." Eventually we worked out that you were talking about your seed potatoes.

Thanks to your vocabulary lessons, and based on the readership of this blog alone, I'd say there are a few dozen Americans who will be more properly prepared to order food if they ever find themselves in a British restaurant.

Anonymous said...

Lol, anything i can do to help...

Patrick said...

This is like the discussion we were having about 'cabbage worms' a few months back on Garden Desk:


Wildacre said...

Hi Kelly and Meg,
Greetings from the Beautiful Lehigh Valley. My wife Karen and I are just north of Easton in Forks Twsp. I happened upon your rain barrel tutorial while googling for barrels for the same type of project! It is going to be very helpful! We have chickens too, 17 bantams at current count, 10 more coming in April.

Hopefully as time goes on we can offer some help back to you!

Best of luck!

Randy said...

Hi Kelly and Meg,
I accidently posted the above comment from my wife's blog, but at least you can see some photos there!

cwilliams11 said...

Thank you, thank you! I am in the process of installing rain barrels and creating a lesson plan for students. Your wonderful details and experience, showcasing your experimental approach and observations, will be incorporated. Thanks for improving my personal installation and for your continued impact on others. Hope to add a link here in the near future.

Rebecca said...

Great project; I admire your inventiveness and thank you for sharing your experience.

Ah, now I see why you raised the first barrel. No harm to it, but I doubt a couple of feet of additional height provides enough water pressure to increase the flow through the system. The bottleneck is still going to be the smallest size/diameter of the connections. Water level equalizes so even a bottom connection will fill in-series barrels.

Very cool project!

Kelly said...

You're right, the raised barrel does help a whole heck of a lot. There are a number of modifications that need to be made, but we will hold off on their application until we move to our own property.