Our Clay Pottery Water Filter
What is it?
Abundant Water’s clay-pottery water filter (CPWF) is low cost, durable, easy to make, simple to assemble, easy to adapt to different conditions and lifesaving.
How does it work?
The filter sits in a bucket of contaminated water.
There are tiny holes on the surface of the filter, big enough to let water molecules through but small enough to stop harmful pathogens.
Our CPWFs are made from local clay and a “burn out material”. We use used-coffee grounds for “burn out”, but you can also use other organic wastes such as sawdust or rice husks!
When the CPWF is fired in a kiln the “burn out material” is burnt away creating the tiny holes that do the filtering.
How do you make one?
1 Source materials in the community
Most materials needed to create Abundant Water’s clay-pottery water filter can be found in rural Lao communities. From the clay and burn-out-material used in the filter itself, to the variety of pipes and buckets used in the completed filter unit.
For our burn-out-material we use used-coffee grounds.
2 Create the filter’s clay
CPWF clay is so easy that almost anyone can make it!
Mix equal parts finely sifted potter’s clay and burn out material. Slowly add water and mix/knead/roll for 30 minutes or so to get proper workable clay.
Traditionally, Lao potters use their feet to mix.
3 Mold the filter
Place the clay in a rigid mold, like a commonly found PVC pipe cut in two, to shape.
4 Fire the filter
For firing, we use a simple open brick kiln powered by local firewood and insulated with another locally sourced material like rice straw.
The filters are fired at 800-900°C.
5 Final assembly
A simple PVC-type plumbing fitting is attached to one end of the finished filter. This can attach to virtually any plumbing configuration.
6 Flow testing
Once finished, each filter is put through a flow rate test to ensure the filter can supply adequate amounts of clean water to its users. This consists of simply passing water through the filter for 2 minutes and measuring the results.
7 Silver application
Filters that pass the flow rate test are then given a fine coating of silver nitrate to act as biocide to kill microbes and therefore provide an added layer of protection.
Our clever, unique CPWF has passed through many transformations since Abundant Water was started in 2008.
Initially, our filters were small and hand-formed so our potters could easily master the technology. The filter was in the form of a ceramic water filter bowl – kind of like a short flowerpot – sitting inside a water receptacle.
After receiving advice from Lao people on the ground, however, we settled on a candle-shaped filter that you see today. Candle-shaped filters are easier to make and provide a high enough flowrate for domestic use.
Our candle-shaped filters have other advantages too. They’re easy to fire. We use a small kiln at our filter production workshop, but villagers can replicate our filters without a kiln, using freely available material, at a very low cost. Firing is as easy as having an outdoor fire with the filters stacked on a mesh base and covered with rice straw.
Another advantage of the candle filter is that you can use commonly available and cheap plumbing fittings to connect to hoses and pipes.