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Saturday, July 2, 2011

Rainwater Harvesting for 3rd World Locations

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Gutters 101 in Rwanda.
 Meant to be a guide for people interested in installing rainwater harvesting systems in remote locations for the use of drinking water.
Rainwater catchment is an ancient technology that can be used to gather water for drinking and other purposes. It is inexpensive, compared to well drilling. The rainfall is currently stable and predictable in Rwanda and the ability of our community to embed and interact with theirs by doing these projects  allows us opportunity to establish relationships and empower them to have improved health and hygiene and assists in creating a local economy and draws congregation to the local churches and gets the different denominations to work together.


When looking at a potential site to harvest rainwater have access and safety be the first consideration. If the building is too tall the risks to members of your team getting injured are greater. If the building is set on a hillside this makes the ladder work more difficult or dangerous.  Sites that are too high must be excluded from potential sites or the work must be outsourced, or safe scaffolding must be erected.
Scaffolding erected in Kirinda, Rwanda

Make a line drawing from an aerial point of view that shows the outline of the building, the dimensions of the roof area and the location of the rain tank. Consider the use of a compass ( which we didn't think to bring ) and indicate on your drawing the side of the building where the work will happen.

Along with calculations of the water yield from the roof it was recommend that we get the name of the pastor or manager, the rough amount of people attending the building and denomination. Get as many pictures as possible of where the gutters will mount in addition to field measurements. Indicate what the mounting surface may be, i.e. metal beams, logs or fascia board, etc.
Water yields are calculated by taking the square footage of the roof, which is length of eave times distance from roof edge to peak, and multiplying that by the inches of rainfall annually. One thousand square feet of roof yield 624 gallons per one inch of rain. The low end average for where we were working is 40'' inches per year, so a two thousand square foot roof with 40 inches of rain per year would yield 49,920 gallons per year on a  average rainfall year, so the yields usually will overwhelm the storage capacity and plans for the overflow discharge should be taken into consideration when deciding the location of the tank foundation. The managers of the locations should be encouraged to use as much water as possible from the tanks during the rainy season whether it was used for crop irrigation or storage in containers, and be educated on the yield per day rationed out over their expected dry season. For example, assuming a 5000 litre tank was full at the start of a three month dry season the amount of water available per day would be about fourteen gallons. The formula is 1,320.86 gallons divided by 90 to equal 14.67 gallons per day for 90 days. Or viewed another way; 60 people per day could have one quart of drinking water per day for 90 days during the dry season.

To see the site evaluations put together by our team CLICK HERE.

Some questions you might answer during your site evaluations;
Is there security or secure storage for tools and equipment? Is there a place nearby to buy drinking water or lunches? Is there power to recharge batteries? If there are no roads that the truck delivering the tanks can drive be sure to arrange for extra man power to carry the tanks in by hand.


Each location where rainwater harvest systems are to be provided should have formed a water committee.  The committee is responsible for providing volunteers to assist in the installation. They should work with the pastors to collect as much money as possible to " buy-in " to their rainwater catchment. They should be encouraged to organize a twice yearly cleaning and inspection of the gutters to maximize the lifespan. By assisting in the installation members of the committee will have the knowledge to repair the gutters if there is a problem. Make sure they know how to use and when to clean the filtration device.

The rainwater system usually consists of; a foundation for the tank, the rain tank, gutters, pipes, wood and fasteners. Also for the water to be safe to drink a filter must be included. Materials for a system that yields as much as 50,000 gallon per year can be as little as $2,000.00, including a Sawyer type filter.


After the site has been selected and the materials ordered the first step in construction is to plan and build the foundation for the tank. Placing the tank on a raised foundation gives a gravity assist to the water pressure and allows for gerry cans or buckets to be filled easily.
Our prototype square foundation.

The foundations we constructed consisted of 2 tons of square cut stone and eight sacks of concrete. The foundation installation should be scheduled for about one week prior to the gutter installation teams arrival so the concrete has time to dry.

The Rwandans use cut rock as filler in the foundation and then the spaces are filled with concrete. Some say a round foundation saves concrete. For our first trip, a square tank foundation was chosen as it allows room for the ball-valve and lock box to have a surface on which to sit. We have since moved on to round foundations with a dedicated area for the nozzle.The advanced preparation step seems critical as the foundations need time to dry, so for maximum success, consider rotating a person or team in a head of the construction team to view, plan and order materials and initiate the foundation construction. Ideally, the foundation would be prepared and all the materials would be delivered to the sites and stored in a secure location prior to the arrival of the team members that would supervise the rainwater systems installation.
17th Foundation in the Karongi District.


Ladder be
 You may be required to trim the beams or modify the building to make the gutters possible. Try to get the locals to do as much of the work as possible so they get experience working with tools and so they feel a greater sense of ownership over what will be their rainwater system.

Beware that they will likely not be wearing safety glasses and may have never handled a power tool before; you must always be on guard to prevent an injury and have first aid items available.

Have extra volunteers on hand to be securing a ladder while somebody works on it, so to minimize injury. The ladders we used had been modified to allow access to a large overhanging roof eave and because of that they were somewhat unstable and wanted to flip. ( PHOTOTIP for working on ladders using both hands ) Designate one person to gather up all sharp metal scraps as the local children will collect anything left on the ground.

Have name tags and markers for the local volunteers so they feel like an important part of the project. Label all water bottles with the volunteers names. There should be one person who's assigned task is site security to protect the backpacks, bags, tools and cameras. 

Creating a straight line for mounting the gutter;
The " Distance Beam " is installed.

You will need to create a straight line where none exists. The method developed by Bob Johnson calls for using one piece of wood to create the mounting surface and a second piece of wood to create a vertical surface, and then a horizontal fascia board. Most buildings have rafters set far apart. In many cases there is ten to fifteen feet between each beam end and this forces a continuous fascia to be installed for the gutter to have proper support.

Here the fascia board with the pre-mounted gutter brackets is being attached to the vertical runner board which is fastened to the distance beam . Beware the heavy weight of the wood and the many sharp screws protruding from the backside of the fascia. 
We cut a notch into a length of drain pipe so that one of our assistants could support the weight of the fascia from the ground.

Our first location had a mixture of metal framing studs and "L" metal. The roof was very uneven. The first step was to place the " distance beams " on each end. Then a string is placed between the end beams and pulled very tight so that the remaining distance beams have a straight line to butt up to.
In this instance the metal beams could not be cut back any more and part of the gutter was set behind the roof edge, so that water would leak behind in a rain. We had to get creative and use extra lengths of gutter, split in two and used to channel the water into the gutter.
This shows a structure with tree branches for beams and rafters. We sandwich the logs between sections of cut lumber and create a larger vertical mounting surface for the fascia board.

After the distance beams are placed The next step is to install the " vertical runners ".

The vertical runners may be 2" x 4" x 10" to allow for the recommended 1/8" per foot suggested slope.

As these initial alignment steps are critical I suggest having the senior mechanically inclined person on your team perform this step.  The distance beams must be both soundly attached and vertically aligned.
This building had a metal fascia and roof. We used blocks of wood to extend the gutter brackets closer to the roof edge so the water didn't overshoot the gutters.

The locals can be utilized to add re-enforcing screws after the initial alignment is finished.
I call the first boards the " distance " boards as they create the distance of the gutter from the wall and determine  where the roof edge is in the context of where the gutter sits. These have  the facing edge cut vertically and the back edge cut to the angle of the wall with the goal of having the new wood look like it is part of the structure of the building. The wood will be crooked, wet and heavy. As you drive a screw into it sap will leak out.
This picture shows the distance beam and vertical runner attached and ready for the fascia.

While the distance beams and vertical runners are being installed onto the building the gutter brackets can be installed onto the fascia board on the ground. Typically these brackets have three screws. The spacing formula  is lineal length of gutters multiplied by twelve to produce inches, divided by however many brackets you have ( but minus two because you don't count the first and last in this math ) equals the spacing between brackets for any given length.
We used a chalk line to mark straight lines on the fascia boards and numbered each section of wood so the brackets could be spaced out and pre-installed, a task well suited to the local volunteers. When we hung the wood the gutter brackets were already on and aligned and the fascia wood itself was sloped towards the tank location. Beware that metal roofs allow the water to gain volume and if the gutters are pitched too hard or sloped far blow the roof edge the rain may overshoot.
We had good luck pre-installing the gutter brackets on the lengths of fascia board as this minimized ladder time.  Reviewing spacing; We had a certain number of brackets to work with on the two locations. On the first location I decided to use 44 brackets in 78 lineal feet, so  coming in from the edges of the fascia board six inches, determine the distance between the two end gutter brackets, multiple the footage times twelve to convert to inches and divide by the number of brackets ( minus two for the end unit already placed ). Example; 78 lineal feet x 12" = 936" divided by 42 equals a bracket spacing of 21.2727273 inches, or 21 and one quarter inch spacing for a total of 44 brackets that would be spread over that 78 lineal feet.
The fascia boards with the pre-installed gutter brackets can now be installed on to the building. We placed a portion of wood on the end of each sections backside, a " joiner board " on each length of fascia board that would allow the following section to be quickly aligned using the chalked line and preset screws.
This is the step where the slope of the gutter is determined. Have one of the project planers " tack " the boards in place using the 1/8" a foot or as needed for slope then have the local assistants go through and add re-enforcing screws after the grade has been established.

Demonstrate to the volunteers how it is that the ladders are to be held and insist that they never deviate from that task. A serious slash or a compound fracture is serious business  in Africa and great care needs to be taken to avoid this.

Each length of fascia had a " joiner " board pre-placed on the backside so that the following section could be quickly lined up and the mounting facilitated. It is shown above as the small block directly above and to the left of the tank, on the back-side of the fascia.

We used plumbers tape as re-enforcing strap to add extra strength to the fascia board. These could in theory be wrapped around the gutter as well; 

As you will have hung fascia board already with pre-aligned gutter brackets the gutter should pop right in. Each section joins together with toothed couplers and the process is straightforward compared to the challenges of alignment that come with installing the distance beams and vertical runners and fascia boards. With the fascia hung with the pre-installed gutter brackets the gutter can now be placed in the gutter brackets and on to the building. We use a plastic hammer to tap the seams tightly together.

The half round gutter is slipped into the back hook of the gutter bracket, and the the front loop is hooked over the bead of the front of the gutter. Place the outlet for the gutter as close as possible to the tank inlet, cutting the gutter sections before and after the outlet with a sawzall. If you have good luck none of the gutter seams will land on a bracket. If they do, you may have to remove the gutter bracket. The plastic is soft and unlikely to break when you are snapping the gutter into place.
The video below shows Rwandans installing the sections of gutters.  You can kind of see the ladder extensions we had welded on to accommodate the larger overhang of the roof line at our second location;
After the gutters are placed into the brackets
Our first project had a very uneven roof line and because of the thick welded iron framing we could not cut the beams back very far, so the roof had to be modified, or something done to prevent the water from leaking behind the gutter. The picture below illustrates how we solved the problem of the roof edge being too close to the back of the gutter;
Sections of gutter split in half with a circular saw was used as a counter flashing because some of the water would have leaked behind the gutter as the roof line was very uneven. Screws were driven through the inverted gutter and into the fascia above the main gutter to hold the flashing in place. A glued, toothed gutter section coupler is visible.

Beware that if the fascia boards are not vertically plumb when they are hung the half round gutter will tend to twist and the face of it bending down or up effects the eye and creates an optical illusion, like the gutter is not sloping towards the drain. As much more slope is used than in a normal Western installation this is okay.  Function, not aesthetics are the most important thing. A sharply pitched gutter will be less likely to clog. A clogged gutter is heavy and makes the system fail prematurely.
Each length of gutter is placed in turn into the gutter brackets with the end piece having a cap, then a coupler is used to join sections of gutters leading to the drainage location which is usually near the center of the building. The drain, or drop-outlet connects to the adjoining section of gutter like the couplers. The end caps work with compression and PVC glue. The installing of the gutter sections themselves are simple and it only takes an eye for detail to seal the seams and couplers thoroughly. No glue should be applied until all the gutter is hung and the initial water test is complete as once it is glued there are no more adjustments possible.
To test the gutters we used a 5 gallon bucket and manually dumped it in near an end cap. If properly installed the water will flow quickly out and in a few minutes the seams can be sealed. A water test is not mandatory but serves well to inspire confidence and demonstrates how the gutters work. Make sure all edges of the teeth of the gutter couplers are glued. Click HERE to see an example of an improper glue job.
All gutter material on our trip was PVC plastic from China that is light-weight and easy to assemble.
The roof was sloped high in the middle at our first location; although in the picture below it looks like the gutter slopes down four inches they were really about 1/8" per foot. We water tested this gutter and it drained dry even though the eye told us that it would hold water.

 This location was difficult in part because the building was set down on a hill and the road made the gutters at perfect eye level and you could see any flaws.When in doubt, test with water. You want to make sure the gutters drain even though  double the normal  amount of brackets are used in these examples. These brackets were spaced about 15" apart. We opted for a tight spacing because there are many filed gutter systems that we saw with wide spacing and sometimes no glue in the seams.

Once all the gutter sections are placed in the brackets, it is time to prepare the rain tank.
We placed the tank on the foundation pad and assembled the sections of drain pipe. The pipe may go back to the wall and into a roof washer, or first flush device, or directly into the tank. We did not have access to pipe couplers so used extra elbows and cut the flanged end off and used those as couplers. We experimented with splitting a short length of pipe to use as a coupler. Other people flange a pipe end using heat but the examples I saw using this method had uneven wall thickness and the pipe appears paper thin. I recommend that pvc couplers be brought in from home with the other project consumables.
After the pipe, or downspout from the gutter is assembled ( without glue ) and routed to the tank, marks are made where in inlet, overflow and bulkhead fittings are to be installed. In hindsight I would have installed a second bulkhead fitting on the two tanks to leave in reserve as that is the weakpoint on a rainwater tank; a child can stand on and snap off the valve causing the tank to drain out.
We used holesaws to drill the three holes. It is advised to have a set of holesaws as the size of the bulkhead fittings vary and in some cases four inch pipe may be used to accomodate large volumes of water. Once the holes are drilled place the tank on it's on the ground and have a volunteer climb inside so that the bulkhead fittings may be quickly installed and a thin layer of silicone caulk can be applied around the fittings. Fumes gather in the new tanks so expedite this process and have the volunteer out of the tanks asap. Once the fittings are installed place the tank back on the foundation pad. Now the final steps can be completed.

This shows the tank with the installed bulkhead and the parts laid out in order; from the tank. A 1" male/male fitting, a banjo valve, a 1" male to female hose barb. All fittings have teflon tape applied and are tightly fitted. Inspect each component for cracks after assembly and replace if broken. Flexible hose was attached to the hose barb and a lock box was placed around the valve.

Once the rain tank is back on the pad and has the bulkhead fittings installed double check that the drain pipes are fitting correctly and then glue them.

Jados completed the installation of the downspout.

A lock box was provided for security and to protect the valves. A metal dedication placard is placed and then the filter assembly is provided.

A Sawyer filter is used to purify the rainwater in our example. A two bucket gravity fed system was provided for each location. Clean plastic buckets were somewhat hard to come by and the stands were made to fit the largest buckets that could be purchased.

Our assistant Jados stands next to the completed filtration assembly.

Other methods may involve ferrocement and manually operated first flush diverters. This guide is specifically for conditions and methods teams from Saddleback Church and members of the P.E.A.C.E. plan developed by Rick Warren  may encounter in our efforts in Rwanda. It is provided publicly  so that other groups may have examples and be facilitated in their efforts to provide clean water to people in need. Every minute, 200 hundred children die due to water related illness. 

Special thanks to My wife and family. Larry and Carolyn McBridge, the Cass family and all the awesome folks at and http://www.nothirstychild/ and Paul Kagame.                                                                                                           

This is a work in progress....


  1. Let no rainwater go to waste should be the world's motto and every building either jointly or individually,should adopt RAINWATER HARVESTING.In this way we would also be able to get more freshwater than what is available to the world now at present and prevent us from any catastrophe in the future in the form of severe water shortage,water wars,water rations,etc.
    In the above link a very good example has been set how rainwater harvesting can be adopted for poorer nations of the world.We want the Governments in the world to act now and spread the message of RAINWATER HARVESTING.

  2. Nice to see some good measures are being taken for rainwater harvesting in such a remote place.

  3. thanks Mr. Alex. this is interesting and probably an installation manual!!

  4. yes Frank it is.
    It was nice doing that with you in Rwanda, and safari to Akagera. Imanna Shimway Inshootay, I may see you again this May.

  5. Hello Alex. Yes I agree with Frank you did a great job with this "Rwandan Rain Water Harvesting manual". You are a godsend for the clean water effort in Rwanda with all your knowledge and teaching efforts. You did a commendable job in Africa with all your hard work and a fantastic write up as always. - Rob A.

    1. Thanks, Mr. Archibald.
      No matter what issues have us at odds currently I will always recall that you and I went to Rwanda together and have room for restructuring.

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  7. Seems like a fun little construction project. Thanks for posting all the pics - they're awesome!
    -Jon @ inlet filter