Introduction: Arbor Loo Composting Toilet for Haiti
Moveable composting toilets that allow fruit or wood-bearing tree saplings to be planted have been used for many years in Africa and now Haiti (see: S.O.I.L.) to encourage planting of orchards by families. This design was for a villiage in Haiti's Central Plateau and is based on those ideas. Four units were constructed using materials available in nearby Hinche at a cost of about $135 U.S. which includes the estimate for labor for 1 day (2 men), construction, transport and installation. An example can be seen at the Kobonal school Notre Dame Ste. Trinite.
The enclosure is constructed of panels of corrugated tin over PVC pipe frames. The tin is attached with loops of baling wire and the panels are joined with baling wire. The roof of the enclosure is sloped toward a drip-edge in the rear where rainwater is directed to a covered bucket with faucet for hand washing. The entrance is a curtain made from a piece of tarp. This results in a light-yet-strong enclosure easily lifted by one person. The enclosure is anchored to a portable concrete slab with 4 bolts and brackets.
The reinforced concrete slab has carrying handles and is thin enough to be carried by 4 men. It supports a pedestal with toilet seat, the enclosure, and a vent pipe.
A 3' x 4' x 3' deep hole is dug and the edge leveled. The slab is placed over the hole and the enclosure and vent pipe attached. The bucket is attached and filled with water. Corn cobs are provided for wiping and a soil+ash+leaf mix provided to aid composting. Flies and odors are reduced by a screened vent pipe and by keeping the lid on the toilet seat closed between uses.
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Step 1: Enclosure: Making the PVC Frames
The enclosure, along with the toilet lid, slab and snorkel-like vent pipe help to prevent water from entering the pit which would reduce the effectiveness of the composting process. The enclosure also provides the occupant privacy and some protection from the elements.
The enclosure consists of 5 PVC frames, 4 of which are covered with corrugated tin fastened with baling wire to form rigid panels. These are the left and right sides, the rear, and the roof. The front frame is not covered but will have a tarp curtain attached later. The panels and front frame are also attached to each other with baling wire to form a light, solid structure when anchored to the slab.
Left and Right sides (this will make the frames for both sides):
You will need:
saw to cut the pvc pipe
4 - 3/4" PVC pipes 46" long
4 - 3/4" PVC pipes 69-1/2" long
8 - 3/4" elbows
Cut the PVC pipes to length according to the dimensions given below.
On a clean, flat solid surface, lay out two long and two short pipes with the elbows for the left side.
Test fit the the parts to make a rectangle. If everything looks OK, apply cement to the inside surface for the first joint in the first elbow and outside end of it's mated pipe. Make sure that the pipe slides in all the way. Repeat for the other pipes -- each time laying the partially completed frame on the flat surface to insure that the frame will lay flat and not be twisted. When completed, set aside the frame and repeat for the right side.
saw to cut pipe
2 - 3/4" PVC pipe 35-1/2" long
2 - 3/4" PVC pipe 69-1/2" long
4 - 3/4" elbows
Make the rear frame just as you made the sides above.
saw to cut pipe
2 - 3/4" PVC pipe 35-1/2" long
2 - 3/4" PVC pipe 47-1/2" long
4 - 3/4" elbows
Make the roof frame in the same way as the previous frames.
saw to cut pipe to length
3 - 3/4" PVC pipe cross pieces 35-1/2" long
2 - 3/4" PVC pipe short sides 3-1/2" long
2 - 3/4" PVC pipe long sides 69-1/2" long
4 - 3/4" elbows
2 - 3/4" tees
Cut the pipe to length.
See the photo above to understand how the front frame is put together. It calls for 3 cross pieces of pipe to form the top, curtain hanger and bottom of the frame. The sides contain two short pieces on the top glued to the elbows of the top cross piece, and the other end inserted in a side of a tee fitting. The center of the tee is glued to the curtain hanger pipe. the bottom of the tee is glued to the long side pipe. and the bottom of each side pipe is joined to the elbows of the bottom cross piece.
On a clean, flat solid surface, lay out the 3 cross pieces, the 4 elbows, the two tees and the short and long side pipes.
Test fit the the parts to make two joined rectangles - a small and a large. If everything looks OK, apply cement to the inside surface for the first joint in the first fitting and outside end of it's mated pipe. Make sure that the pipe slides in all the way. Repeat for the other pipes and fittings -- each time laying the partially completed frame on the flat surface to insure that the frame will lay flat and not be twisted.
This completes the Frame assembly. Next step, Enclosure: Covering the Frames
Step 2: Enclosure: Covering the Frames
Covering the Sides, Rear and Roof:
Note: For these panels, the idea is to attach the outer edge of the tin to the PVC pipe beneath with a loop of baling wire at 1 foot spacings. and where the tin sheets overlap they are stiched together with the baling wire at 1 foot spacings. This makes a strong, yet light panel.
The side and rear panels are the easiest to cover as the tin extends to the outside edge of the frames. If you purchased the tin in 6' lengths you will only need to cut along the length of 1 sheet for each panel. The roof frame is shorter and has an overhang so that panel will be built last.
Tools you will need:
pin punch or nail set
2-1/2' - 3' 2x4
laundry or similar permanent marker
Left panel, Right panel and rear panel:
2 sheets 6' corrugated tin
Put on your safety glasses.
Lay the frame for the left side on a hard flat surface.
Lay one of the 6' sheets of corrugated tin over the long side and against the left edge of the frame. There should be no tin overhanging any side of the frame. Take the next sheet of tin and lay it so that the right edge of the sheet is lined up with the right side of the frame. The two sheets will overlap by about 1-1/2 to 2 feet. Where the sheets overlap you will need to cut the overlapping sheet about 3" past the point of overlap from the top to the bottom. Mark this point on the top sheet at both ends, then remove the top sheet and cut it between those two marks with the tin snips (do not cut the bottom sheet).
Place the scrap piece of tin aside and place the cut sheet back in place over the whole sheet.Look at the edge of where the top sheet overlaps the bottom sheet. If the last 1-1/2 inch or so does not form a valley, then turn the sheet over so that the edge of the overlapping sheet DOES form a valley. This will make it easier to stitch the panels together later.
Using the marker, start at the top left corner of the panel and make a dot about 1-1/2" from top and left side in the nearest valley. (Two wire loops here will fasten the corner of the sheet to the pipe below later). Repeat this for the other three corners. With a ruler or tape measure, start at a corner dot and measure 1 foot along the edge of the panel to the nearest valley and mark another dot 1-1/2" from the edge of the tin. Repeat this process all around the perimeter of the panel. These dots will later be punched with the pin punch or nail set to attach the tin to the PVC frame.
You will now be working in the valley at the edge of the top sheet where it overlaps the bottom sheet. Start at the top of the frame and measure 1 foot down along the base of the valley. Place a dot in the center of the valley of the overlapping sheet. Continue along the valley 1 inch further and mark another dot. (These will later be punched and a wire looped through to stitch the sheets together.) Continue along the valley placing double dots to stitch the sheets together at 1 foot intervals.
Remove the PVC frame from beneath the two sheets of tin. Place the 2x4 under the valley where the sheets overlap and make sure that the top and bottom of the two sheets are aligned. punch the holes through both sheets where the two sheets will be stitched together (along the valley of the top overlapping sheet). Using the wire cutters (and wearing the safety glasses) hold the end of the wire which will be cut off about 5" in length and cut the wire. Bending the wire into a U shape so that it can be passed through the two holes spaced 1" apart, pass the wire through the topmost two holes and twist them together on the other side at least one turn with your fingers.
Cut another 5" piece of wire and pass it through the bottom most two stitch holes and twist as before. With a helper standing the two sheets upright, you can now cut and pass the remaining wires through the remaining stitch holes and twist them.
Using the pliers (and this takes practice so don't be discouraged if you break a few wires) twist the wires at least three turns and until there is no slack between the wire and the overlapping tin sheets. (You will be able to tell the binding is tight if you wiggle the pliers while holding the wire and the wire does not move easily.) If you break a wire, just pull it out and replace it. There will be pigtails that must be cut off with the wire cutters after twisting. Make sure that you have your eye protection on and hold the end of the wire which is being cut off. This will prevent the cutting from flying in your or someone else's face. When the pigtails are cut off, you must take the pliers and turn the twisted end toward the tin so the occupant does not get scratched. Pass your hand gently over the finished binding to make sure it is safe. Always do this for the bindings.
Now lay the joined sheets on a flat surface and place the 2x4 under an outside edge of the tin. punch the remaining holes along the perimeter of the tin moving the 2x4 backing as necessary.
Remove the 2x4 and place the tin over the PVC frame. Cut 8 pieces of wire about 6" long. Pass two wires through the top left corner hole so that one wire wraps around the left pipe and the other wire wraps around the top pipe. Twist the wires hand tight for now. Repeat this for all 4 corners. Now you can either work on the ground or have a helper stand the panel up for you to wrap all the way around the perimeter of the frame. Tighten the loops with the pliers as before and cut the pigtails. Turn the sharp twisted end toward the PVC pipe or the tin to avoid scratching the occupant as before.
The right side is assembled exactly as the left side.
The rear panel is assembled in exactly the same way as the left and right sides.
The Roof panel:
Like the sides and rear panel, three sides of the roof panel are aligned with the edge of the PVC frame and wrapped with wire.
Unlike the other panels, the tin on one of the short sides of the roof will extend 3" beyond the PVC crosspiece below it to receive the gutter later, so the hole punching is a bit different on that end.
You will need two sheets of tin and the small roof PVC frame.
Place the roof PVC frame on a flat surface.
The left and right sides of the frame are longer than the front and back sides. With this in mind, place the first sheet of tin over the top left corner of the frame aligning the edges of the sheet with the outside edges of the top and left PVC pipes. The corrugations (hills and valleys) should run parallel with (in the same direction as) the left side. The bottom of the sheet should extend a few feet past the bottom PVC pipe. Place the second sheet over the first and align it's right side with the right outside edge of the PVC pipe. Mark where the sheets overlap by 3" on both ends of the top sheet. Remove the top sheet and cut it with tin snips along this line. Lay the top sheet back in position over the bottom sheet and mark 3" past the outside edge of the bottom PVC pipe on both overlapped sheets (in other words, the tin sheets will be 3" longer than the frame). Draw a line with a straight edge between these marks and cut each sheet along that line with the tin snips.
Place the scrap tin aside and lay the second (top sheet) back over the first sheet. Look at the edge of where the top sheet overlaps the bottom sheet. If the last 1-1/2 inch or so does not form a valley, then turn the sheet over so that the edge of the overlapping sheet DOES form a valley. This will make it easier to stitch the panels together later.
With the sheets back in position over the PVC frame, make a dot near the top left corner at about 1-1/2" from the top and left edges in the nearest valley. Repeat for the top right side. Make dots 1-1/2" from the left, top and right sides at 1' intervals as on the other panels. Where the tin overlaps the bottom PVC pipe (extends 3" past it), you will put two dots at 1' intervals (in the nearest valley) which straddle the pipe below -- 1 dot to the left of the pipe below 1 dot to the right of the pipe below.
The left, top and sides are stitched as for the other panels and the bottom is stitched by looping the wire through the two holes and around the bottom PVC pipe. Tighten, cut and bend safely as before.
End of Enclosure: Covering the Frames. Next up: Enclosure: Assembling the Enclosure
Step 3: Enclosure: Assembling the Enclosure
Assembling the Enclosure:
With a helper holding the left panel and the rear panel together at a 90 degree angle, cut a lengths of wire sbout 8" long and loop them through the holes nearest the top and bottom edges where the panels are touching. Twist them together one turn by hand. Repeat for all 1' interval holes in between. repeat for the right side, front and top. Twist the wires tightly with the pliers, cut the pigtails as before and turn the sharp ends toward the pipe or tin. The resulting enclosure should look like the one below. If so, CONGRATULATIONS!!!!!
The privacy curtain should be weather resistant. (I was able to buy a plastic tarp locally and it made enough curtains for 6 toilets.)
The curtain can be cut to the height and width of the opening plus a little more for doubling the thickness at the top for hanging strength and at the sides for better coverage of the opening. The top edge of the curtain is folded over a few times and holes punched every 3 or 4 inches in the center of the fold. Cut lengths of baling wire and make loops to go over the curtain rod and through the holes. You will need one wire for each hole. The bottom of the curtain should hang just above but not touch the bottom PVC crosspiece.
End Enclosure: Assembling the Enclosure. Next up: Rainwater Capture System
Step 4: Rainwater Capture System
The rainwater capture system:
The rainwater capture system consists of a gutter, downspout and covered bucket with fawcet. This facilitates hand washing after use of the toilet. In the dry season, the bucket can easily be filled with water from any nearby clean water source.
You will need:
dril with 7/8" blade bit
2 - 3" PVC pipe 19" long
1 - 3" PVC tee
2 - 3" PVC endcaps
1- 3" PVC 24" long
1 - 5 gallon bucket with lid
2 - 3/8" rebar 16" long
1 - 3/4" fawcet (hose bib)
A 1-1/4" strip must be removed from the side of each of the two 19" PVC pipes. The resulting slot will allow the pipe to pass over the lower edge of the roof to act as a gutter and catch rainwater. The 3" tee also has a slot cut across the top of the tee but at a 45 degree angle between the top and side of the tee. The two 19" pieces are glued to the tee with the slots lined up and endcaps glued to the other ends of the 19" pipes. It may be necessary to wedge the cut piece of pipe into the slot until the glue has dried for a tight fit. If that doesn't work, use screws to attach the pieces together.
Attach the completed gutter to the 3" extension of the roof with at least two pieces of baling wire.
Each piece of 16" rebar will form a hanger to hook the bucket handle. from one end of the rebar, measure 1-1/2" and make a 90 degree bend. go another 1-1/2" and make about a 100 degree (wider) bend. on the other end of the rebar, measure 1-1/2" from the end and make a bend in the opposite of the first two bends forming a U or hook. Hang each of these hangars over the top of the rear wall panel on either side of the 3" tee.
Insert the 24" pipe downspout into the 3" tee, but don't glue it.
Cut a 3-1/4" hole in the center of the bucket lid (you can use a piece of 3" pipe as a template.) and push the lid over the end of the 24" downspout.
Hang the bucket on the hangars with the end of the hangars on either side of the bucket handle. The hangars should be the same length and the bucket should hang straight. If not, make necessary adjustments.
Using a 7/8" blade bit, make a hole near the bottom of the bucket on the side facing away from the rear wall panel. The hole should be about 1/2" above the bottom. Gently, but firmly thread the fawcet into the hole until the fawcet is firmly seated and the handle is facing up. Put some water in the bucket and test it for leaks. If it leaks, try making a gasket and placing it between the fawcet and the outside wall of the bucket. A good choice is rubber inner tube or something similar, but glue or caulk might work also.
Remove the bucket, lid and downspout. They will be reassembled at the installation site.
End Rainwater Capture System. Next up: Pedestal
Step 5: Vent Pipe
The vent pipe aids in removing odors and controlling flies.
You will need:
1 - 6" square of fly screen
1 - 3" PVC pipe 74" long
1 - 3" PVC pipe 4" long
2 - 3" PVC elbows
Using the rasp, take a little material off the outside bottom end of the 74" PVC pipe to facilitate insertion in the slab later.
To the top of the pipe glue a 3" elbow. Next Glue the 4" pipe to the other side of the elbow. Finally, glue the second elbow to the 4" pipe facing down to prevent water from entering the pipe. Place the 6" fly screen over the end of the elbow and fasten it with baling wire.
(The vent pipe will be passed through the opening between the left wall and the roof at the installation site and inserted into the 3" hole in the slab.)
Step 6: Pedestal
The pedestal provides a clean, comfortable seat for toilet use and is mounted over the larger
hole in the concrete slab.
You will need:
drill with drill bits
small nuts and bolts
sand (some small gravel is OK)
To simplify the pedestal form, the pedestal is poured upside down, so the extension for the toilet seat hinge is at the bottom.
The two halves of the pedestal inner shell are joined together with small nuts and bolts to form a 12" diameter cylinder that is 14" tall. A 12" round plate is attached to the top of the cylinder to prevent flexing when the form is being filled. The cylinder sits on the sheet metal base.which is shaped like a ring to form the rim of the toilet where the seat will lay with an extension at one end. The three sides of the extension are bent up from the base and are 1-1/2" tall. A plate covers the extension and one side is wrapped around the end of the extension to hold it in place and the other two sides hang over the sides of the base. 3/8" holes are drilled 5-1/2" apart on the cover plate and base of the extension and contain two 5/16" bolts wrapped with tape. When the form and bolts are removed from a completed pedestal, the resulting channels will receive the toilet seat hinge bolts.
The outside shell is about 15" in diameter (the walls of the poured pedestal will be about 1-1/2" thick.) and 14" tall. It is formed from one sheet which has been bolted together where the ends overlap. The bolts of the overlap face to the outside away from what will form the wall of the pedestal. A notch is cut out where the extension is located for the poured concrete to pass through into the covered extension. Finger tabs extend out from the bottom of the outer shell and are bolted to the base. The top of the outer shell also has finger tabs that are bolted to a round ring to hold the other shell rigid at the top during pouring.
Using a 1:4 cement to sand mix, fill the pedestal mold while periodically tamping the
mix down to be certain that it fills the seat-bolt mounting extension area. When mixing, the
consistency should not be too thin but should allow the concrete to flow.
You will see some seepage around the bolt holes and at joints.
Cure the pedestal for one week, then carefully remove mold in the reverse of assembly.
If the poured cement receded from the top of the ring as it dried, you put too much water in
the mix. If the concrete did not fill the mold completely, you may not have tamped the cement
enough or the mix may have been too thick to flow well.
A group of farmers from Ohio arrived at the mission where I was working on this project with black plastic drainage pipe for use as the pedestals of the composting toilets - a quicker and lighter solution to be sure. They also went with a smaller 2" vent pipe. I have included the following pictures courtesy of Roger Borchers as an alternate method of construction. Great job guys!
End of Pedestal. Next up: Reinforced Concrete Slab
Step 7: Reinforced Concrete Slab
A reinforced concrete slab covers the composting pit and supports the enclosure, pedestal and
vent. It is light enough to be moved by 4 men .
The slab form has a 2" deep by 3'-6" x 4'-6" inside measure. The wooden frame is held
together on the sides with screws that are removed when the slab is cured to allow lifting the
slab free of the form. The base of the form is sheet metal which is permanently attached to the
side frame.There are two holes in the slab - the 12” diameter hole for the pedestal and the 3”
diameter hole for the vent pipe.
You will need:
1 - 80 lb sack of cement
some sand and gravel
4 - 1/4" rebar 52" long
5 - 1/4" rebar 40" long
4 - 3/8" rebar 25" long
4 - 5/16" x 3" bolts and nuts
For the form you will need:
drill with driver bit and drill bits (3/8")
deck screws (will be reused)
1 - 2x4 cut into two pieces 55-1/2" long and 2" wide
1 - 2x4 cut into two pieces 43-1/2" long and 2" wide
1 - piece of sheet metal 57" long and 45" wide
4 - pieces of angle iron about 18" long with small holes for screws drilled at each end and a 3/8" hole in the center
1 - 2" high base of a 5 gallon bucket
1 - 3" PVC pipe 2" in length
Assemble the cut 2x4 pieces as shown above to form a rectangle frame of depth 2" using screws.
Attach the 57" x 45" piece of sheet metal to one side of the frame with screws. Turn the form over so the sheet metal is at the bottom.
Drill a hole in the center of the bucket base and another hole in the bottom of the form at the position where you will want the pedestal to be mounted. turn the bucket base upside down and bolt it to the form (the threaded end of the bolt should be facing up). A good position for the hole in the sheet metal of the form is about 1-1/2 feet from the short end of the slab.
On the opposite end of the slab which will be the front left corner, measure about 8" from each side of the corner to mark the center of the hole on the tin where the 3" pipe will be placed. Place the pipe over this hole and make a circle with a marker around the inside edge. Remove the pipe and using tin snips carefully cut in a radial pattern from the center of the circle to the marked edge. Bend some of these fingers up and attach them to the 3" pipe with short screws. This will form a hole for the vent pipe later.
Place the angle iron brackets at all 4 corners of the form and attach them with screws.
Hang the 5/16 x 3" bolts in the holes with the head of the bolts down. The threads of the bolt should extend about 2" about what will be the top of the slab, so put spacers as necessary.
The 1/4" rebar is placed within the form in a grid of 4 vertical bars and 5 horizontal bars laid in the
pattern indicated by the photo. Tie the rebar at every place where they cross with baling wire.
Bend the 3/8" rebar for the handles every 5” to form a handle with bent legs such that the handle tilts outward slightly when placed in the form (the angle of the legs will be greater than 90 degrees). Place the handles on the longest sides of the slab near the corners
and against the side edge of the form to not interfere with the walls of the enclosure. Tie the handles to the 1/4" rebar grid where they overlap.
The concrete is mixed in a ratio of 1 part cement to 4 parts sand/gravel mix. and is poured to a depth of 2". Use the screed board to level the concrete and finish with the trowel.
The slab must not be moved for one week, after which it may be removed from the form and installed at the site.
To remove the slab from the form, remove the angle iron corners and the 4 screws that hold the 2x2's together. Do not remove the screws that hold the sheet metal base of the form to the 2x2's. Remove the nut that holds the bucket base in place and tap with a hammer around the edge of the bucket base to loosen it. Tap the 2x2 frame boards with the hammer to loosen them from the sides of the slab. They may tilt out some and that is OK. Tap around the top edge of the 3" pipe to loosen it from the slab. Starting at one corner and tapping frame, pipe and bucket base as necessary, have your helper lift one of the handles enough for the bottom of the slab at that corner to clear the top of the wood frame. At that point, place one of the angle iron brackets between the slab base and the corner of the form and let the helper gently rest the slab on the angle iron. Repeat this at the other three corners until the slab is completely free of the form. The slab may then be lifted by 4 men and placed on the ground for transport. It is easiest to move the slab if strong poles are passed between the handles to aid in lifting and carrying whenever possible. Be careful as the concrete slab is estimated to weigh more than 300 lbs.
End of Reinforced Concrete Slab.
Step 8: Making Mounting Brackets
Once the slab has been removed from the form and placed on the ground, it is time to place the enclosure on the slab and make some mounting brackets to fasten it to the slab's anchor bolts. This will be the last step before moving everything to the final site for installation.
Using bar stock, c-channel or similar material cut the material to length so that it will clamp down over the base of the PVC frame and can be held down by bolting the slab anchor bolt through a 3/8" hole in the bracket. Do this for all 4 corners of the enclosure. Unbolt the enclosure from the slab for transport.
Step 9: At the Installation Site
Dig a hole with level sides in a sunny location clear of overhanging trees approximately 36" x
48" x 36" - 42” deep where a sapling tree is to be planted later.
Make sure the sides of the pit are level to provide good support for the slab.
Center the slab over the hole. Make certain that the hole is completely covered.
Back fill soil around the outside edge of the slab and tamp it down well to insure that the pit is
place the enclosure on the slab, insert the vent pipe through the left wall opening and into the 3" hole in the slab, then fasten the enclosure to the slab with the 4 anchor bolts and metal brackets.
Place the pedestal over the larger slab hole and seal with a 1:10 mortar' Install the toilet seat and close the lid.
Insert the 24” downspout in the 3" Tee of the gutter and then attach the bucket with lid to the
hangers and fill the bucket with water.
Provide some corn cobs and soil-ash-leaf mix (3 soil to 1 ash and some leaves) for the family and instruct them on the use of
the toilet as follows (instructions should be translated to Kreyol):
TOILET USE INSTRUCTIONS:
Keep toilet lid closed between uses
Corn cobs are for wiping after doing twalet , then throw it in the pit hole.
Put a cup of soil-ash-leaf mix in toilet hole after doing twalet but NOT after pee-pee
Always wash your hands after use with water from the fawcet.
Refill corn cobs and soil mix (3 soil to 1 ash and some leaves) as needed.
When the pit is full, dig a new pit 3’ x 4’ x 3’-3” deep, unbolt the enclosure from the slab,
remove the pedestal, then move the slab over the new hole and reassemble.
Cover the old hole with about 6” of soil and plant a tree sapling. Putting leaf mulch around the base of
the sapling will help to keep the soil moist. Water frequently until the tree begins to root well.