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self-watering bog garden

A step by step guide for building my new self-watering bog planter

Self-watering bog planter


A Brief description of the self watering bog

  • The system is self-watering.
  • Each planter holds 30 quarts. There are two planters in this photo.
  • A single float valve tank (on right) controls the water level for all connected planters.
  • The system is modular, allowing additional planters to be added easily.
  • The valve tank and each planter are on individual PVC stands with adjustable legs for adjusting water level as well as stability.
  • The tanks will be painted - they are shown unpainted here. The plastic is probably not UV stable, so paint will provide protection against UV.
  • The system has been through some initial testing. So far it performs well. Some additional tweaking may be necessary to dial in the water levels when put into service. I'll post updates on the performance once they have plants in them.



General Construction Guidelines

  • All 3/4" PVC pipe lengths provided include the 3/4" length necessary for fitting connections.
  • All PVC pipe connections should be glued using PVC pipe cement unless noted otherwise.
  • Make sure your space is well ventilated for fumes from glue and melted plastic.
  • Electrical conduit PVC is grey, and plumbing PVC is white. For the 3/4" pipe the type is not important. I used both simply because I had some of each already. The 3/4" PVC conduit slip to male or female thread fittings are grey, and the fact that they are electrical fittings is very important. Threads on these electrical fittings are not tapered, so they can be tightened to be flush. This is important for the bulkhead fittings and the feet. Plumbing fittings have tapered threads to make them water tight. The bulkhead fittings use an 'O' ring to make them water tight.

Float Valve Tank

Float Valve Tank Parts List

  • 1 - Little Giant Water Trough Float Valve ( available at agricultural supply stores )
  • 3 - 1/4" x 3/4" nylon bolts
  • 3 - 1/4" nylon nuts
  • 3 - 1/4" nylon washers
  • 1 - Rubbermaid 12 quart "snaptopper" storage bin with lid. Dimensions: 16.3" x 11.1" x 6.9"
  • 2 = #18 'O' Rings
  • 2 - 3/4" PVC Conduit slip to male thread fittings
  • 2 - 3/4" PVC Conduit slip to female thread fittings
  • 2 - 3/4" PVC 90 elbow
  • 1 - 3/4" PVC Tee
  • 1 - 3/4" PVC ball valve
  • 3 - 3/4" PVC pipe cut to 2.0" in length
  • 1 - 3/4" PVC pipe cut to 1.5" in length
  • 1 - 3/4" PVC pipe cut to 2.75" in length

Little Giant Float Valve


This is the valve that was in my old wooden planter. 2 new 9/32" diameter holes must be drilled into the top of the valve so it can be mounted to the underside of the lid of the 12 quart Rubbermaid container. The third hole in the center was already there.


Float Valve Tank Top


Using the float valve as a guide, transfer and cut holes for mounting and the water connection into the Rubbermaid container lid. The small holes are 9/32" in diameter, and the large hole is 1 3/8"


Float Valve Tank Top


Mount the float valve to the underside of the lid using the nylon nuts, bolts, and washers. The Float can be carefully snapped out of the valve body to access the mounting holes.


Float Valve Tank Top


A top view of the float valve mounted to the underside of the 12 quart container lid


Float Valve Tank Bulkhead Connections


The bottom of the 12 quart container will serve as the float valve tank. Using the 3/4" Conduit fitting as a guide, mark a spot for a hole for a bulkhead connection. There will be two bulkhead connections to the valve tank, one for the overflow stand pipe and one that connects to the drain valve and the planters. The bulkhead connections should be in opposite corners. There is not much room so position is critical. Be sure there is clearance for the thickness of the PVC fitting, and be sure that there is sufficient surface for 'O' ring contact.


Float Valve Tank Bulkhead Connections


Use a 1" spade bit to carefully cut a hole in the tank. Use a scrap of wood to back the cut, otherwise the plastic will split. This hole is slightly too small for the 3/4" male threaded end of the PVC conduit fitting. Carefully sand the opening to make it just large enough for the male thread of the PVC conduit fitting to pass through without binding.


Bulkhead Connections


A bulkhead connector is created using the PVC conduit slip to male and female 3/4" fittings. The 'O' ring is used to create a water tight seal. Ideally an 'O' ring should be in a groove, but since the ring is slightly smaller than the male thread it works fine as long as it is not distorted by over-tightening.


Bulkhead Connections


Fit the #18 'O' Ring onto the male threads of the PVC fitting.


Bulkhead Connections


Secure the PVC conduit fittings with 'O' ring in the hole in the tank for the bulkhead connection. Tighten the connection for a good seal, but do not overtighten. Do Not Glue Threads . All of the bulkhead connections in this system will be made the same way as shown here.


Drain Valve Tee


Set the ball valve to the CLOSED position (the valve is open in the photo) when gluing the valve to ensure there is enough clearance to the side of the tank for the valve handle to operate. The valve handle may need to be positioned away from the tank for clearance. Connect the Tee and the ball valve to a bulkhead connector using the three 2" lengths of PVC pipe and one of the 90 elbows. The hose barb connector shown here is be covered in the tank to tank connection section.


Stand Pipe


Connect the 90 elbow to a bulkhead connector using the 1.5" length of PVC pipe. Press fit do not glue the 2.75" stand pipe into the elbow. This stand pipe will need to be cut to set the highest allowable water level above the level where the valve shuts off. The stand pipe can be glued once all final adjustments are made and the best length is established.


Planter

Planter Parts List (Parts for ONE planter)

  • 2 - Rubbermaid "Snaptopper" 30 quart storage bins without lids. Dimensions: 22.8" x 16.7" x 7"
  • 1 - 3/4" PVC Conduit slip to male thread fitting
  • 1 - 3/4" PVC Conduit slip to female thread fitting
  • 1 - #18 'O' Ring

Planter - shown complete with plumbing attached to the bulkhead connectors next to the float valve tank.


One of the 30 quart bins is used as the planter tank, and the other is used as a liner that holds the planting medium. The tank for the planter needs to have bulkhead fitting(s) added in the appropriate corner(s) depending on the number of planters. If you have only one planter, then you need only one bulkhead fitting, and it should be on the long side of the container such that it can connect to the float valve tank. Follow the same procedure for creating the bulkhead connection as was done for the float valve tank.


Planter Tank Liner


The foot on the 30 quart container that is used for the liner needs to be notched to provide clearance for the bulkhead fitting in the tank.


Planter Tank Liner


A large nail is heated with a propane torch. The heated nail is used to make the holes in the bottom of the planter liner.


Planter Tank Liner


Making the holes with the heated nail should be done in a well ventilated space. I used a hot nail rather than a drill because the plastic tends to split easily should the bit snag.


Planter Tank Liner


The completed grid of holes in the bottom of the planter liner. The holes allow the water from the tank to soak into the planting material.


Planter Tank Liner


The completed tank with liner, pictured here beside the float valve tank.


Planter Tank


These spacers are short pieces of PVC that are placed in the center of the tank and help transfer the weight of the liner to the center leg of the planter stand.


Tank to Tank Connection

Tank to Tank Connection Parts List


  • 2 - 3/4" slip to 3/4" female thread PVC plumbing fitting
  • 2 - 11/16" to 1 1/4" hose clamps
  • 2 - 3/4" MIP to 3/4" hose barb adapter
  • 1 - 3/4" I.D. 6.5" length flexible hose
  • 3 - 3/4" PVC pipe cut to 1.5"
  • 1 - 3/4" PVC 90 elbow
  • pipe thread tape


Tank to Tank Connection


Connect a 3/4" slip to 3/4" female fitting to the Tee opposite the drain valve using a 1.5" PVC pipe. Connect a second 3/4" slip to 3/4" female fitting to the bulkhead connector on the planter tank using a 90 elbow and two 1.5" PVC pipes. Wrap thread seal tape on the male threads of the hose barb adapter. Screw the hose barb adapters into the 3/4" slip to female fittings.


Tank to Tank Connection


Connect the barbs together using a 3/4" I.D. length of flexible hose and the hose clamps.


Planter Tank




Close up views of the planter tank connection to the float valve tank


Float Valve Tank Stand

Float Valve Tank Stand Parts List

  • 4 - 3/4" PVC Tee fittings
  • 4 - 3/4" 90 Elbows
  • 4 - 3/4" PVC Conduit slip to male thread fitting
  • 4 - 3/4" PVC Conduit slip to female thread fitting
  • 2 - 3/4" PVC pipe cut to 5.0" in length
  • 2 - 3/4" PVC pipe cut to 6.0" in length
  • 8 - 3/4" PVC pipe cut to 1.5" in length

Float Valve Tank Stand


The 6.0" PVC pipes form the cross members that span the shorter dimension of the tank. The 5.0" pipes form the sides of the stand that are parallel to the longer dimension of the tank. Four 1.5" PVC pipes attach the elbows for the legs. Four additional 1.5" PVC pipes connect the 90 to the adjustable feet which are made up of the threaded conduit fittings. Do not glue the pipes that connect to the feet to the 90 elbow. The weight will hold the feet place, and allowing the feet to be removable provides a way to adjust the leg lengths, if necessary.


Float Valve Tank Stand


A close up of the fittings and 1.5" pipe that make up the adjustable feet. These pieces should not be glued.


Planter Tank Stand

Planter Tank Stand Parts List

  • 7 - 3/4" PVC Tee fittings
  • 4 - 3/4" 90 Elbows
  • 5 - 3/4" PVC Conduit slip to male thread fitting
  • 5 - 3/4" PVC Conduit slip to female thread fitting
  • 2 - 3/4" PVC pipe cut to 5 3/8" in length
  • 4 - 3/4" PVC pipe cut to 5.5" in length
  • 2 - 3/4" PVC pipe cut to 11 3/4" in length
  • 5 - 3/4" PVC pipe cut to 3.5" in length (legs)
  • 4 - 3/4" PVC pipe cut to 1.5" in length


Planter Tank Stand


The two 11 3/4" pipes form the cross members that span the shorter dimension of the planter tank (white pipes in the photo). The two 5 3/8" pipes connect to the center leg. The four 5.5" pipes form the sides of the stand that run parallel to the longest dimension of the planter tank. Four 90 elbows are connected to the frame with 1.5" PVC pipes. The legs and adjustable feet are formed by the five 3.5" pipes and the threaded conduit fittings. Four legs are at the 90 elbows, and one leg is in the center connected by the center Tee fitting. The legs should not be glued so they can be adjusted for height if necessary. Note that the legs on the planter tank are 2.0" taller than the legs of the float valve tank stand. This difference in height is important for the correct water level. When the water level in the float valve tank reaches a level that will shut off the valve, the resulting water line needs to be approximately 1/2" above the bottom of the planter liner in the planter. The 2.0" leg length should get the water line very close to the correct position. The legs can be adjusted to get the level set.


Planter Tank Stand


One of the legs formed by the 3.5" PVC and the threaded conduit fittings. These parts should not be glued.


Complete Tanks on Stands


The float valve tank and two planter tanks are shown here without the tank top and liners.


Complete Planter


The completed system. In this photo there are two planters connected in series to the float valve tank. Note the height difference in the legs to help set the proper water line in the planters. Since the plastic in the storage bins is likely not resistant to ultra violet light, the bins will be painted to protect them.




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Copyright Charles S. McFalls, Jr.