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rainwater catchment

How do we get enough pressure from a rainwater catchment system?

Posts: 4

Location: Long Island

posted 12 years ago

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I am planning to be off the grid in less than a year. I am planning a rainwater catchment system in the back of my house that will be commected to the house plumbing. The tank will be large. I hope to build it out of insulated concrete forms possibly 6 feet wide x 3 feet deep x 20 feet high. I am hoping there will be enough gravity fed pressure to suit the needs of my house. bathroom shower etc.

My question is how do I know there will be enough pressure when I turn on the fauset? is there any math formula to determine the pressure when the tank is full or 1/2 full? Any ideas?

Brian Knight

Posts: 554

Location: Asheville NC

posted 12 years ago

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Theres quite a bit of math in that which may be tough to know the variables for at this point. Gravity will probably not provide enough pressure for all but the most basic needs. Planning on a pump is probably in order.

"If you want to save the environment, build a city worth living in." - Wendell Berry

Joe Braxton

Posts: 320

Location: NC (northern piedmont)

posted 12 years ago

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Average household water systems operate at 30 - 80 psi. with 45 psi. being a good target. You could probably get by with less, but that would be a decision you would have to make.
1 psi. (static) of water is equal to 2.31 ft. of head, so 45 psi. will equal over 100 ft. of elevation above your faucet (not the ground).
No doubt you will need a pump to achieve pressure you are used to seeing.

Handy converter -
http://www.convertunits.com/from/psi/to/foot+of+head

John Polk

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Location: Currently in Lake Stevens, WA. Home in Spokane

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posted 12 years ago

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When that size of tank is full, it will contain over 20,000 pounds of water, so elevating the tank becomes impractical. If you are relying on gravity feed, you will only be able to utilize water above the level of your faucet. If your shower head is 7 feet above the bottom of the tank, you will not have any flow when the water level drops to 7 feet.

Yacht and RV stores carry 12V water pumps (RV stores are probably a lot cheaper than yacht stores).

One pump I have read a lot of good reviews (by off grid users) on is this one:
http://www.northerntool.com/shop/tools/product_37142_37142

Beverly Johnson

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Location: Long Island

posted 12 years ago

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Thank you for the respnses. The pump is described as on demand. Would I need to turn it on and off everytime the water is used or could it supply water to the system up to the right psi?

John Polk

steward

Posts: 7926

Location: Currently in Lake Stevens, WA. Home in Spokane

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posted 12 years ago

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"On demand" means that it is pressure sensitive. When pressure drops, (you open a faucet) the pump kicks on. It should remain on as long as the water is flowing. Once you shut off the faucet, it will again build up pressure (to whatever it is set to), and then shut itself off again.

If you hear it frequently cycling, when not using water, that means you probably have a leak somewhere.
An occasional cycle (when not using water) is not abnormal, as pressure changes can be expected with temperature changes.

You'll be a 'happy camper' once you get off of city lights and city water. Good luck.

Angelika Maier

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Location: Zone 10a, Australia

posted 12 years ago

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The most common thing is to have a pump. We are connected to town water and have our own so we use a pump as our plumbing system is a pressured one.

Medicinal herbs, kitchen herbs, perennial edibles and berries: https://mountainherbs.net/ grown in the Blue Mountains, Australia

Jeremiah wales

Posts: 137

posted 12 years ago

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Pressure for what use?
I have a 500 gallon Storage tank on a "Water Tower". It is only 6 ft in the air from the ground and even with the bottom of my roof eves. But water flows fine out of my faucets, toilet and into the Tub. Now a Shower is another thing. I had to hook up a 12 volt pump to get my shower to spray out. But then I used a low volume shower head there.
I saw an appliction once where someone made a shower. They took a five gallon bucket with aprox 30 holes in it at the 7 ft mark and filled it with hot water. Took a shower under it.

Dave Turpin

Posts: 112

Location: Groton, CT

posted 12 years ago

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The pressure we are used to seeing at the tap is there not to make our life easier, but simply to ensure that everyone who is serviced by that water has sufficient pressure to operate their appliances.

In most cases, the water that comes out of your faucet or appliances has been dropped down to atmospheric pressure by a valve. This is why most faucets are either needle or globe valves, and gate and ball valves are only used as main cutoff valves in the system. (The purpose of a needle or globe valve is to drop pressure)

Off-grid houses that use pressure tanks and pumps are doing so simply because they are using plumbing designed for houses with pressurized water mains. You don't NEED to do this, however. As long as the bottom of the cistern is above the highest point of use, water will flow, you just need to use plumbing designed for low pressure use!

Now, this isn't as EASY as simply using off-the-shelf plumbing components. You will have to engineer each appliance you want to use. sinks, tubs, and toilets are easy. Showers will require a different kind of head (I would say a "rain" head with the restrictors removed would work fine). Hot water storage and use, washing machines, etc., will require further thought.

Jeremiah wales

Posts: 137

posted 12 years ago

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Wow, I can see I have a different take on Living off the Grid than most people these days. But then I have shirts that are older than many people on this forum.
When I hear of living off the Grid it does not seem like a huge thing to do, It all takes adjustment. When I think of it. I consider it saving money, Not spending money to say you are saving money.
I have lived a basic lifestyle for that past 45 years. Keeping costs down, No Dishwasher, No Special appliances. Basic stuff. My water is heated with wood, My house is heated with wood. Not that I bought, that I cut and got for free. Storage water flows just fine out of every faucet and into my toilet very easily. No I dont think I can an automatic dishwasher with my water flow. But that is because my dishwasher is me.
How much do you really save catching water and then using it for regular lifestyle? To me it would cost more to catch it and save it than it I would save.

Kacy Wallace

Posts: 17

Location: Austin, Texas

posted 11 years ago

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Jeremiah wales wrote:Pressure for what use?
I have a 500 gallon Storage tank on a "Water Tower". It is only 6 ft in the air from the ground and even with the bottom of my roof eves. But water flows fine out of my faucets, toilet and into the Tub. Now a Shower is another thing. I had to hook up a 12 volt pump to get my shower to spray out. But then I used a low volume shower head there.
I saw an appliction once where someone made a shower. They took a five gallon bucket with aprox 30 holes in it at the 7 ft mark and filled it with hot water. Took a shower under it.

Hi Jeremiah. I have a 275 gallon rain tank encased in a galvanized steel cage. I'm researching ideas on how to elevate it. I was considering using concrete masonry units (CMUs), but would be curious to know how you elevated your tank safely, which is much larger. By my calculations, my tank will weigh over 2,500 pounds when it's full.

Alder Burns

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Location: southern Illinois, USA

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posted 11 years ago

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I recently put four such water "totes" on top of a shed. I reinforced the interior with some 4X4 braces near the corners of each tank....all of one edge is along one wall. It is a stoutly build shed with 2X4 framing and plywood sheathing, floor, walls, and roof. It's been comfortably holding up 10K lbs. of water all summer. Of course I had to pump the water INTO these tanks, but it will flow fine by gravity out of them, and is at sufficient height to run a shower (provided, as stated above, that the showerhead is low pressure. I made one out of the "rose" of a watering can one time!). Getting a barrel or tank even six feet up in the air will run drip tape. If the site has any elevation differences at all, one can contrive to have tanks or cisterns near the high point and then gravity feed the whole site. At one of my places in Georgia we had a well placed near the high point of the property and then ran water to cabins and gardens downhill from there. The well was on direct-solar with a float valve in the tank, so it would top up automatically.
An additional advantage to low-pressure, gravity-fed water systems is that most of the plumbing can be done with garden hoses! These are easy to work with, easy to repair leaks, and are not as likely to be damaged by freezing.....

Richard Nurac

Posts: 52

Location: north Georgia

posted 11 years ago

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Having sufficient water pressure and avoiding airlocks needs planning and experimentation. Most of my catchment areas are at the bottom of the hill and I pump to two 285 gal tanks at the top of the hill from which I irrigate my plantings. Rainwater provides all my irrigation needs and wellwater my personal needs. The system requires frequent supervision since algae does grow and clogs my low pressure bubblers and drippers. But it is satisfying, efficient and, as water shortages loom, ensures that my well (or my neighbors' wells) will not run dry because of my irrigating. My website has details and pics.

www.nu-trac.info - new life tracks – growing organic, conservation, self reliance

Corey Schmidt

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Posts: 244

Location: Kachemak Bay, Alaska (usda zone 6, ahs heat zone 1, lat 59 N, coastal, koppen Dfc)

posted 7 years ago

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If i understood the original post right, the proposed water tank would be 20 feet high, meaning there would be 20 feet of vertical water in it when full. if that's the case, please be sure you properly engineer it!!! I had a tank 5 feet high explode (twice) due to the weight of water in it. it was made of wood and built in too much of a hurry, some fasteners were forgotten....but 20 feet, thats a whole other story. even if you have plenty of continuous rebar, and you will definitely need it horizontally as well as vertically, you will need to make sure somehow your mortar joints don't blow out. Also, there is a reason most water tanks are cylinders, its much easier to have structural integrity with that shape.

Tiffaney Dex

Posts: 63

Location: La Bretagne

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posted 1 year ago

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Jeremiah wales wrote:Pressure for what use?
I have a 500 gallon Storage tank on a "Water Tower". It is only 6 ft in the air from the ground and even with the bottom of my roof eves.

Hello. Would you be willing to post photos and describe the structure you built to hold up the weight of your water storage tank?

Anne Miller

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posted 1 year ago

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Tiffany, since this was a post from 2013 you might not receive a reply from Jeremiah. I do hope that Jeremiah will see your reply and respond.

Here is some information that might answer your question.

When you build your water tower be sure to take a picture to share and to get a PEP Badge Bit:

https://permies.com/wiki/144199/pep-plumbing-hot-water/water-tower-plumbing-straw-watertower

This thread might also be of interest to you or others:

https://permies.com/t/62997/Calculating-PSI-water-tower-system

Here are some other examples I found on Pinterest:

source

Invasive plants are Earth's way of insisting we notice her medicines. Stephen Herrod Buhner
Everyone learns what works by learning what doesn't work. Stephen Herrod Buhner

Tiffaney Dex

Posts: 63

Location: La Bretagne

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posted 1 year ago

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Thank you very much Anne for posting this video and pictures. It was very kind and helpful of you. If we do build a water tower for pressure, instead of buying a small pressure tank, i will post pictures. But I don't quite know what badges are, so not for that reason.
Take care

John F Dean

master steward

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Location: southern Illinois, USA

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posted 1 year ago

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Hi Tiffany,

Much depends upon the volume hence weight of the tank and it’s height relative to the faucet. If the elevation was, say, within 6 ft of the ground and the tank capacity was in the hundreds of gallons range …or more… I would consider setting it on a concrete block structure. To have a 300 gallon tank of water collapse can add some excitement to the day. I have 150 gal water tank sitting on a 6 ft tall concrete block foundation. The bottom of the foundation is 8 ft above my garden. The purpose of the tank is to collect water to water my garden.

At my age, Happy Hour is a nap.

Anne Miller

steward

Posts: 16099

Location: USDA Zone 8a

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posted 1 year ago

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We have well water and use a pressure tank.

At our other house we used a tank similar to the first picture I posted to water the garden.

The Badges are from the PEP Permaculture according to Paul and PEA Permaculture Experience Anywhere.

These are part of the Skip: develop the Skills to Inherit Property.

I find them fun to read and see what other folks are doing.

Invasive plants are Earth's way of insisting we notice her medicines. Stephen Herrod Buhner
Everyone learns what works by learning what doesn't work. Stephen Herrod Buhner

Tiffaney Dex

Posts: 63

Location: La Bretagne

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posted 1 year ago

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Hi John. Thank you for the reply. Right now, we have three cubes up on two layers of concrete blocks where the ground level is about an additional twenty meters higher than the house. Unfortunately, last fall, lightning struck our house (along with all the neighbors) through the aerial lines and it went from our house to the water containers, breaking some of the blocks closer to our house as it went into the ground. Now the first cube has a slow leak. And we're disconnected from the grid.

Since the first cube is pretty useless now, we want to change the system. With the current system, I can feel up the washing machine. But we don't have water to our faucets. I'd like something att least two meters higher than our house to have running water, and two to three cubes, meaning two to three thousand kilograms, plus a few more with the containers, i believe.

My husband is leaning towards the idea of just stacking up cubes on a concrete foundation so that we have bottom layers for watering the garden and the upper layer for household usage, as that seems like the simplest and easiest idea. Do you know if the cubes can support the weight of one and two cubes of water on top of it?

Tiffaney Dex

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Location: La Bretagne

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posted 1 year ago

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And thank you, Anne, for your second reply. Is the pressure tank in your house and how does the water get into it?

Are the badges the words next to the username?

Anne Miller

steward

Posts: 16099

Location: USDA Zone 8a

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posted 1 year ago

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The pressure tank is about halfway between the well and the house. The pressure tank lives in a building we built that covers it.

I have seen pictures here on the forum where people put the pressure tank in a storage building where they can store other stuff.

An underground pump (I think) pumps the water from the well to the pressure tank.

When we turn on a faucet inside the house water comes out of the faucet.

One morning the water did not come out of the faucet so I called the "Well guy" to come to see what was wrong. It was something (again I think) attached to the pressure tank.

I hope this has painted a picture so you can understand.

Invasive plants are Earth's way of insisting we notice her medicines. Stephen Herrod Buhner
Everyone learns what works by learning what doesn't work. Stephen Herrod Buhner

Tiffaney Dex

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Location: La Bretagne

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posted 1 year ago

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Anne, do you have a pressostat on the line to turn on the pump? And, if so, where is it in the line arrangement?

John C Daley

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posted 1 year ago

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Tiffany, RV have 12 or 24V self starting pressure pumps that I have been using for many years.
Sureflow is one company.

John Daley Bendigo, Australia The Enemy of progress is the hope of a perfect plan
Benefits of rainfall collection https://permies.com/t/88043/benefits-rainfall-collection
GOOD DEBT/ BAD DEBT https://permies.com/t/179218/mortgages-good-debt-bad-debt

Anne Miller

steward

Posts: 16099

Location: USDA Zone 8a

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posted 1 year ago

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Tiffaney Dex wrote:Anne, do you have a pressostat on the line to turn on the pump? And, if so, where is it in the line arrangement?

I have no knowledge other than what I have presented.

The well was here when we bought the property.

We had the "well guy" come out to tell us about the well and move the pressure tank to a better location.

You might start a new topic with all your concerns and maybe someone with an answer will speak up.

I you have a well or are going to have one this forum would be the place for your questions:

https://permies.com/f/164/wells-springs

Invasive plants are Earth's way of insisting we notice her medicines. Stephen Herrod Buhner
Everyone learns what works by learning what doesn't work. Stephen Herrod Buhner

John F Dean

master steward

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Location: southern Illinois, USA

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posted 1 year ago

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Hi Tiffany,

Without examining the cubes, I couldn’t be sure. Even then, my opinion would be questionable.

At my age, Happy Hour is a nap.

Stephen B. Thomas

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Location: Wheaton Labs, Montana, USA

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posted 1 year ago

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I skimmed through these responses, and so far I've not seen mention of a foot pump. We use these at Basecamp all the time for the outdoor sinks for washing stations. The model is designed as a "galley pump" for boats.

It is, by far, a less-common solution. And you will need to do something so that the water inside the pumps doesn't freeze in the winter temps. But you ought to be able to use them without having a water tower, just some hose to go from the water reservoir to the pump, then the pump to your faucet. No electricity is required.

Here's what we use at Wheaton Labs for these functions:

https://www.fisheriessupply.com/whale-gusher-galley-mk3