Building the Cob and Green Roof Garden Wall – Part 4: The Cob and Reclaimed Sink Water Fountain


To give our wall a little curb appeal from the barn road and to get experience plumbing in cob structures we decided to incorporate a water feature in to the T junction buttress. Conveniently, around this time, the barn was getting a spring clean and an old porcelain sink was pulled out and left for the taking. We took it!


To get this sink to hold water we took a trip to the local hardware store and fitted it with a new drain assembly. Rather than have a pump cycle water from within the sink we elected to connect the sink to a sump that could be hidden within the wall. This way the pump and tubing would be concealed in the wall and the fountain would look neat and tidy from roadside.

To do this, we commandeered a 5 gallon bucket and fitted it with a DIY bulk head according to the excellent article found here. We then connected the drain of the sink to the bulkhead-fitted 5 gallon bucket using PVC such that the sump sat higher than the sink (so that if the system fails the water will overflow out from the sink rather than out from the sump and in to the wall). We tested it for water tightness prior to installing it in the wall.



In the meantime we sculpted the T junction of the wall to accommodate the sink, bucket and plumbing. We left the area of the wall that sits below the plumbing assembly cob free so that if the plumbing decides to leak it will drip directly in to the stone and concrete foundation and be able to trickle away through the gravel trench fill.


The cob wall behind the sink is sculpted to hold the bucket sump and to allow any leaks from the pvc plumbing to drip directly in to the foundation and away from the wall.


Once the fountain was sitting comfortably, we cobbed up the walls around the side to the height of the top of the sink basin.


Then we installed a custom arch form which we covered in newspaper as described in previous posts. We then continued to cob up and over it to make an arched fountain housing.


Behind the fountain, in the cob wall, sat the sump bucket. To conceal this we used a piece of 3/4″ ply and layed it horizontally across the cob walls surrounding the bucket housing once they were a few inches proud of the top of the bucket but lower than the backing plate of the sink. A hole was drilled through this ply wood roof piece to allow for outflow hosing to be run from the pump back to the sink through a fountain spout. The plywood roof allowed us to continue the main part of the wall over the bucket housing and in to the T junction, creating a roofed nook to hide the bucket which also created a back wall to the arched fountain housing from which the fountain spout emerged.


In this photo you can see the cob that is being applied on top of the plywood roof plate so as to form a continuous wall and also create a back wall to the fountain housing. Also visible is the pvc tube which is housing the flexible tube running between the pump and the copper outflow spout.


The fountain spout is made from a piece of 1/2″ copper tube cut at a bevel and connected to the pump by way of flexible tubing that runs from the pump in the bucket, up through the hole in the plywood roof piece, and then makes a soft 90 degree bend within the cob on top of the ply to exit through the back wall of the fountain arch housing. This flexible tubing runs inside 1.5″ PVC tubing to prevent it getting compressed by the cob. We found a nice smooth rock in our cob pile which we drilled out to create an ornament around the fountain outflow spout as a finishing touch.


The finished outflow spout with drilled rock and beveled copper tubing.


Finally the roof was sculpted to flow with the rest of the wall.


Cute roundy roof profile.


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