Water Systems

How to Build a Gravity Fed Water System

One of the most basic ways to build a running water system is the gravity-fed system. It consists of a cistern or holding tank at a higher elevation than the point of use. This allows gravity to do all the work of moving the water through the system eliminating the need for a water pump whether mechanical or electric. 

Contents

  • The Water Cistern or Holding Tank
  • Elevation
  • Filtering and Purifying
  • Construction
  • Types of Plumbing
  • Coupling and Flush Valve
  • Future Planning
  • Draining the system and system Shut-off

Water Cistern or Holding Tank

A cistern can be any size to suit your purpose. We use a 275-gallon IBC tote we purchased used for $30. It’s important to make sure whatever container you get is of food-grade quality.  You can usually purchase larger cisterns from farm supply stores or local farm coops. 

 If you use an IBC tote as we did you need to know that the connection points at the valve where you would thread plumbing fittings aren’t all the same. I wanted a tote that would be compatible with a standard 2” PVC fitting. The way I made sure I got the correctly threaded tote was I simply took a 2” fitting with me when I went to get the tote; Finding the tote I liked then threading on the 2” fitting.   

It’s also important to regularly look inside your cistern to see if it needs to be cleaned. If sunlight is allowed into the tank algae will grow and it will need to be cleaned periodically. Certain types of algae can be harmful to humans so don’t take this lightly. 

Elevation 

The cistern has to be elevated above the point of use. This can be done by constructing a tower, by putting the cistern on the roof or by placing the cistern on a hill at a higher elevation. 

The amount of pressure at the point of use will be determined mainly by the difference in elevation between the point of use and the cistern. the formula to calculate pressure is Pressure=.443*elevation in feet. This will come out to be 1 psi. For every 2’4” 

The advantages of a tower are you can build where it is most convenient for you and you can build it as tall as you want. The disadvantages are that you will have to find a way to pump the water into the cistern and the construction will get costly especially as it gets taller. 

Putting a cistern on the roof has the advantage of lower cost because you’re already going to build the structure where the cistern will be placed. Considerations in the construction of the roof will have to be made to accommodate the extra weight, but the cost savings will still be significant.

The disadvantage is the height will be predetermined by the height of the roof and you will still have to figure out how you’re going to pump water into the cistern. 

Placing the cistern on the land at higher elevation is the simplest solution because no tower or structure is needed to elevate the cistern and the amount of elevation is only limited by the topography of the land and it can be done in a way that allows water to be added to  the cistern fairly easily if the water is being hauled to the location.

The disadvantages are this set up will likely be the least convenient. The cistern is probably going to be a good distance from the point of use. And there will be some added cost because there will be a lot more plumbing pipe needed for this setup. The longer distance of plumbing pipe will also add some resistance to the water flow but it is minimal. 

Filtering & Purifying 

Whether you’re hauling water from a local source, pumping well water into the cistern or collecting rainwater you want to have a method for filtering and purifying your water. 

Bottleless Water Coolers

Treating your water is as simple as putting 1 tablespoon of bleach in your cistern for every 100-gallons. This just kills harmful bacteria so you’ll still need to filter the water to remove particles. 

Unless you’re getting your water from a municipal source you need to filter it to remove particles that may be harmful or at the very least can rack havoc on your plumbing fixtures. Modern fixtures are made with very small orifices which can easily be plugged and are sometimes impossible to get cleaned. So, take some time to come up with a plan to filter your water. 

A whole house filter is a good option because it filters everything coming into your cabin. These systems are fairly inexpensive and pretty simple to install. These filters are great at removing particles but aren’t designed to purify the water. I would recommend at least a 2 stage system using one filter to catch only large particles than a second filter to catch small particles. In the long run, this will make your filters last longer thus lowering your overall cost.

Click on the picture below to shop the many whole house filter system options available.

We’ve been using a Brita batch filter for our drinking and cooking water every day since 2014 with great results. The filter itself is inexpensive and the replacement filters are too. I would highly recommend Brita for a batch filtering system. 

Ideally, a bio-sand filter is the best option for an off-grid homestead because it will filter and purify your water at the same time in one system and once you’ve built it and seasoned it there are no other costs. No replacement filters to buy no Clorox or iodine etc. 

Construction 

Now that you have your cistern in place and you know how you’re going to filter and treat your water it’s time to hook it all up. This is pretty straight forward in that you connect all your plumbing pipes in your cabin to a mainline that connects to your cistern. There are some other considerations to make maintenance and repairs in the future a much simpler task. 

Types of plumbing pipe 

I used 1 ½” poly pipe to run from my cistern to the cabin and I used ¾” pex to run all the main lines for the water supply lines. Finally, I used ½” pex for all the individual water supply lines to the fixtures. This step down in size doesn’t increase water pressure, but it does increase water velocity which seems like better water pressure at the point of use. 

You can also use PVC, copper or galvanized steel pipe. I have found that the poly pipe is very durable and inexpensive and pex pipe is extremely efficient and easy to work with. Pex fittings are a little higher than PVC, but the amount of time saved in installation and repairs is quite substantial.  

Coupling and flush valve 

At the point where the mainline connects to the cistern, a coupler fitting will allow you to remove the cistern for cleaning without having to redo all the plumbing fittings to reconnect to the cistern. This will be just as useful if you ever want to upgrade your cistern. 

Click on the image below to shop coupler valves.

Directly after the coupling, you can install a T fitting with a shut-off valve going to the mainline and a shut-off valve on a line that dumps into a drain or into an irrigation tank. This can be used to clean or flush the cistern by closing the valve to the mainline and opening the valve to the flush line that dumps into a drain or irrigation tank. 

Future plans 

I would also install T fittings and plugs in places where you think a future plumbing project might happen. For example; when I ran our plumbing in our cabin the only fixture we had was a kitchen sink, but I made room in the plumbing lines with Ts and plugs for future additions. When I went back to add the bathtub, water heater and washer the plumbing lines were ready to go. 

Draining the system and system shut-off 

It is also handy to have a shut-off near the cabin to stop water flow from the cistern to the cabin. This allows for repairs and improvements while the cistern may be full of water. You will also want to have a drain valve at the lowest point in the system. This will allow you to drain the water from the entire system if needed or to just drain the water from the cabin while leaving the cistern full of water. 

Please leave any specific questions you may have in the comments. I read and respond to all of them and I use your comments to improve the content on this site.

For a very comprehensive look at rainwater catchment and gravity-fed systems I highly recommend the following book. Click on the picture below to check current price on Amazon.

Modern Potable Rainwater Harvesting shows how to design, build, and maintain a rainwater system that consistently and reliably provides potable water that is orders of magnitude cleaner than typical public municipal water. The book covers advanced oxidation processes, disinfection, biofilm control, filtration, plumbing, electronic controls, and water testing. Electronic schematics of essential control circuits are provided. Plumbing diagrams for both on-grid and off-grid systems are provided. Proper pump sizing for a given storage capacity is discussed. The book shows how to use a spreadsheet to properly size storage capacity based on actual rainfall data, collection area, and assumed daily usage rate.

To check out all the other books about off-grid living that I like and recommend go to my recommended books page.

https://offgridmaker.com/recommended-books/

m

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Water Systems

Water Options For An Off-grid Homestead.

When making your off-grid plan there are a few very important questions to answer. Where will my water come from? How will I make it potable? What will be the delivery mechanism? This article is going to describe 6 systems for off-grid water solutions.

  • Hauling water 
  • Live body of water 
  • Drilled well 
  • Hand dug well 
  • Rainwater harvesting 
  • Gravity Fed water system 

Hauling water 

Hauling water is the simplest way to have water because no systems are needed. You don’t need a well or pumps or a source of electricity to run pumps etc… You just need a source of water (river, lake, municipal water, melting glacier or whatever is nearest you) and a way to get it and bring it home.  

When my wife and I first moved to our raw land we hauled water from a nearby neighbor’s hand dug well in 1-gallon jugs while I started to hand dig our well. Then we got some 3-gallon jugs. Now I have a trailer with a 275-gallon tote and we haul water from a local reservoir.  Our hand dug well is at this time unfinished. Hauling water allowed us to move off-grid even though our permanent water system is still incomplete. 

This should be considered a temporary solution as it’s costly in time, energy and fuel, but it does allow you to begin your off-grid journey before you have the permanent water system in place. One of the greatest benefits of hauling water is it really forces you to pay close attention to the amount of water your consuming on a daily basis, especially if your hauling only a few gallons at a time. Keep in mind the way to self-sufficiency is a journey of many steps not a leap from the beginning to the end. 

Live Body of Water 

If your property has a body of water like a lake, river or even a live stream you can use it as a source of water. This will require a way to pump the water into a cistern or holding tank. From there you can use that water for irrigation, but if you want to use the water for drinking, cooking or household water you’ll need to have a filtering system in place.  

Moving water sources like rivers and streams have the added benefit of the kinetic energy of the flowing water that can be used to pump the water without the use of electricity from the river or stream to another location.  This can easily be done with what’s known as a ram pump. Another option would be a water wheel pump. Both of these pumps can be purchased or home built.  Of course, you can use electric pumps to deliver the water to where you need it. 

Once this water is in a storage tank you can treat it with one tablespoon of bleach for every 100 gallons to kill bacteria then filter it to remove particulates or you can build a bio sand filter to eliminate the bleaching step. There are many water filtering systems on the market for sale, but don’t be afraid to build your own filtering system. Humans have survived for a very long time without these complicated and sometimes very expensive filtration devices.   

Drilled Well 

Having a drilled well system on site is the most convenient of all the solutions. It’s basically on demand water like with municipal water systems, but it’s also the most expensive. Having a well drilled can cost thousands of dollars and in some areas with no guarantee water will be there.  

 It also requires an electric pump for delivery of the water. The deeper the well is the larger the pump will have to be and these pumps are energy hogs. In recent years solar well pump costs have begun to come down, but a solar well pump system is still going to start around $2,000 for just the pump and the controller. It’s not going to include the solar array, batteries, charge controller or installation. 

There will also be a cost in maintaining a drilled well system because there are several components to this system which will wear out over time. You have to decide for you if the cost of this kind of system is worth the convenience it provides. 

Hand Dug Well 

If you’re in an area where good water can be found shallow then a hand dug well is an option.  Hand digging a well is an extremely physical task, but while it will cost you a lot in sore muscles and aching joints it has very little cost beyond that. 

Our hand dug well at 16’deep

You can haul water by hand from the well, you can install a mechanical pumping system or you can utilize an electric pumping system. A hand dug well has more flexibility in how it can be used and it will cost less, but it won’t be as convenient as a drilled well and it will take a lot of work.  

Hand dug wells were the norm 100 years ago so don’t be afraid to tackle it. It’s very gratifying to reach that level of self-sufficiency. To dig your own well by hand and know that from that moment on you will have access to the second most important thing on the planet for your survival. 

Rainwater Harvesting 

Rainwater harvesting can be a very convenient option because it can be done using the structure where the water will be used so delivery mechanisms will be inexpensive. The methods for collecting rainwater are simple and the materials used can be purchased at the big box lumber yards.  

The amount of water that can be collected adds up quickly. For every 1” of rainfall on 1,000 sqft. of the collection surface approximately 600 gallons of water will be collected. When you also think this water falls freely from the sky with no effort on your part it’s surprising that more people don’t harvest rainwater. 

That being said it’s even more surprising that in some places in the US it’s illegal to collect rainwater so check your state and local laws before you invest the time and resources to collect rainwater.  

Gravity fed water system 

A gravity fed water system uses the force of gravity to supply running water to a structure without the use of any power source. The basic idea is the water source is a cistern or tank elevated above the point of use.  This will produce pressure in the system allowing the water in the system to flow from the tank to the point of use. Many people will ask; how much pressure is in a gravity fed system? The simple answer is it depends on the difference in elevation between the point of use and the holding tank. A simple formula to get you close is Pressure=.433 x height. More simply put, for every 2’4” of difference in elevation between the point of use and the holding tank 1 psi will be created. There are other variables which can slightly affect the psi at the point of use, but this simple formula gets you close. The real advantage to this type of system is in its simplest form there are no moving parts to wear out with the exception of the valves in faucets. The differences in elevation can be achieved by building a water tower, but then you have to consider how water will be pumped into the tower. We found a property with big steep hills. our storage tank is near the top of one of the hills and our cabin is down hill from the tank. When I haul water in our trailer I park at the top of the hill and hook up a hose from the trailer tank to the storage tank and let it drain in.

for a more detailed description of how to build an off-grid gravity fed water system check out my post “How To Build a Gravity Fed Water System”https://offgridmaker.com/2019/05/11/how-to-build-a-gravity-fed-water-system/

For a more in depth look at off grid water system Check out this article by Maximum Off Grid https://www.maximumoffgrid.com/off-grid-water-system/off-grid-water-system-guide/

It really doesn’t mater which water source you use. You can even do combination of multiple sources. Figure out what will work best for you and start planning it out. If you have any questions or would like help making a water plan please leave me a comment.

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