• Go to Home

Ceramic Water Filters

Ceramic water filters provide affordable high quality drinking water, at a household or classroom level, for communities who are otherwise without access to safe drinking water.

Resource Development International Cambodia (RDIC) has been making ceramic water filters in Cambodia since 2003. RDIC’s operation started at a small scale as it developed its manufacturing techniques. By September 2007 RDIC had distributed approximately 60,000 filters throughout Cambodia, and internationally, with 24,000 produced in 2007. Ceramic water filters have proven to be tremendously effective in reducing the exposure of users to contaminated water, and the incidence diarrhea over an extended period of time (Brown and Sobsey, 2006). RDIC continues to invest significant time and energy into developing its processes and would like to share its knowledge and best practice approaches with organisations who wish to have a similarly positive impact on communities in developing countries. While the technology is simple, adherence and commitment to best practice manufacture, training and education is essential to ensuring the ceramic water filters provide the high quality, safe drinking water that its users require for good health.
The five key features of the RDIC Ceramic Water Filter Programme that have led to its success are:

  1. the appropriate, simple, yet highly effective design of ceramic water filters,
  2. a manufacturing and quality assurance process that ensures only high quality filters are distributed,
  3. a manufacturing process that is inexpensive, using locally available and sustainable materials,
  4. an education programme that informs people about the value of clean water, how filters work and how to take care of their filters and use them effectively, and
  5. a distribution network through schools, communities, local business and other non government organisations (NGOs), that provides an ongoing contact point for filter replacements, purchases and queries.

Download the desired options.

Handbook. Updated on Mar 05, 13
Download RDIC Ceramic Wate Filter Handbook Version 1.3 (.pdf, size 2.83MB)

Appendices as Compressed RAR Files. Updated on Mar 11, 09
Download Appendices A, B, C, D, E package. (rar compressed filessize 3.79MB)
Download Appendices F, G, H, I, J, K package. (rar compressed size 4.38MB)

Resource Development International – Cambodia (RDIC) and Engineers Without Borders Australia (EWB Australia) are excited to release the RDIC Ceramic Water Filter Factory Manual.
This project has been the result of considerable work from RDIC staff and three volunteers from EWB Australia since 2007.
RDIC would like to see the number of communities with affordable and sustainable access to safe drinking water increase and also to provide skills improvement and employment opportunities.

This information package aims to provide information on all elements of the manufacture, education and distribution of water filters to facilitate the introduction of factories to new communities with maximum success.

This handbook:

  1. discusses how ceramic water filters work, highlighting supporting information on their efficacy in the field;
  2. documents the manufacturing process for RDIC’s field proven low cost household ceramic water filters;
  3. presents key issues for setting up a ceramic water filter factory;
  4. presents alternative methods and lessons learnt based on RDIC’s experience of manufacture over 5 years;
  5. identifies key issues of occupational health and safety, and environmental management;
  6. discusses the essential components of education and distribution and their importance for sustainable implementation of filters in communities;
  7. presents technical drawings for key machinery that has been developed for use in the factory; and
  8. includes instructional videos for production of the ceramic water filters.

The pot with the silver lining video


Field trials of the effectiveness of ceramic water filters in Cambodia over time showed a 46% reduction in diarrheal disease between filter users and non-users, a 95.1% average (and up to 99.99%) reduction of E.coli in drinking water (Brown and Sobsey, 2006). Laboratory testing has shown a 90-99% reduction in viruses (Brown, 2007). These results support other trials of ceramic water filters (Lantagne, 2001) as a highly successful means of empowering households to manage their own safe water supply.

The actions of the RDIC Ceramic Water Filters are:
  1. Physical ‘straining’ of dirt and bacteria out of the water as they are too large to pass through the ceramic substrate.
    1. clay that has been vitrified through firing in a kiln changes chemically to become a slightly porous material allowing water to pass through its but straining out most bacteria, protozoa, and helminthes.
    2. burn-out material is added to produce pores that increase the rate of flow through the pots to make them a practical filtration material
  2. Chemical action of silver as a biocide to kill microbes.
    1. silver applied to inside and outside of filter is absorbed into the clay pores.  Silver ions are reduced to elemental silver and form colloids within the filter body.  Silver acts as a biocide against bacteria when there is sufficient contact time.
  3. Indirect sedimentation of particles within the pores of the filter.

RDIC now adds laterite to its clay mix.  Laterite, a material high in Fe oxides, the positive charges of the Fe oxides have demonstrated a removal action of the largely negatively charged virus’ in tests at RDIC.


The Handbook steps through the production process used by RDIC in Kean Svay, Cambodia.  This process can be described in 10 steps as summarized below.

10 Steps










1. Preparation of Raw Materials


Clay and laterite (optional) is crushed into powder, rice husks are either purchased pre-ground from a regular supplier or can be ground on site; water supply

2. Mixing of Clay Components


Clay powder, laterite (optional), and ground rice husks are dry mixed, then water is added evenly and mixed thoroughly to form a mouldable paste

Clay Mix
30 kg clay powder + 8.9 -10 kg rice husks + 12.5 L water

Clay Mix (when laterite is added) 30 kg clay powder + 7.5 – 8.8 kg rice husks + 12.5 L water + 2 kg laterite

3. Forming Clay Cubes for pressing


Clay mix is emptied from the mixer and pressed into 8kg cubes for easy pressing.

4. Pressing of clay cubes into ceramic filter form


A hydraulic press is used to press the clay into the pot shape.

5. Surface finishing and labeling of pressed filter elements


Filters are checked and smoother, and scraped with plastic to ensure even surfaces. Poor formed filters are reformed into cubes and repressed. After initial drying filters are stamped with date and batch number.

6. Drying of pressed filter elements – to remove initial excess water


Filters initially dry for several days to remove water before firing in the kiln.

7. Firing of filter elements in kiln – to finish dehydration and vitrification


Firing temperature is initially low to allow final drying, then temperatures are increased to about 866˚C.  Clay material is changed chemically, rice husks burns out leaving small cavities.

8. Flow-rate testing of fired filter elements


Following firing, and cooling, filters are soaked completely, then filled and quantity of water that flows out in 1 hour is measured. Optimal flow rate is 1.8 – 2.5L/ hour. If the flow rate is too high, it may indicate internal cracks in the filter and therefore ineffective filtering. Additionally, a very high flow rate means there is insufficient contact with the biocidal silver. Flow rates that are too low, will make their use impractical in the home.

9. Painting of silver biocide solution on surfaces of filter elements


A silver nitrate solution is painted onto the inside and outside surfaces of the filter element. Silver is biocidal and can kills bacteria and algae on contact.

10. Packaging of ceramic water filter system (plastic holder etc)


The filter package includes the ceramic filter element, plastic ring for support, plastic receptacle, faucet, and maintenance instructions.

Next Steps

Initial Considerations – Setting up a Ceramic Water Filter Factory

The Handbook discusses relevant considerations to take into account when setting up a ceramic water filter factory including:

  1. Are ceramic water filters right for you?  Ceramic water filters are suitable for treating the most common risk to drinking water quality – contamination with biological pathogens – as well as for removing general macro contaminants such as dirt and plant matter. They are not suitable for treating water whose primary health risk is chemical – such as arsenic.  They suit households, workplaces, and classrooms, and their implementation should be supported by education and a sustainable source of information and replacement parts.
  2. Where to set up the factory? Locating a factory near source of raw materials, energy and water needs, near your market’s population centres, on major routes to assist distribution is valuable.  Noise and fumes of production and its impacts on surrounding community should be considered.
  3. Sourcing Inputs.  Sourcing key inputs including clay, burn-out material, kiln fuel, energy, water, and plastic receptacle manufacture are major aspects of setting up a ceramic water filter factory.  Many of these choices will vary based on your location, available materials, and the costs and options will vary significantly between countries (eg the price of electricity, appropriate burn-out material, fuel for kilns).
  4. Machinery.  Lists the key machinery sed in RDIC’s manufacturing process, approximate cost etc.  Machinery, excluding the kilns, flow rate testing baths, and flow rate testing racks which are built onsite can be estimated at around $13,000 US in Cambodia at this time.
  5. Factory Layout Briefly Common sense approaches to factory layout can maximize efficiency of production from day one by minimizing both horizontal and vertical distances for moving items around the factory, reducing double handling, and providing surfaces that allow trolleys and wagons to be used.
  6. Staffing.  Staffing policies are important considerations during the set up phase.
  7. Establishing your manufacturing process.  Both flow rates, and kiln firing regimes need to be established for individual factories.

Education and distribution

RDIC employs a number of different methods to ensure filters become accessible to community members following manufacture including through:

  1. schools;
  2. direct sales through private distributors and RDIC; and
  3. non-government organisations (NGOs).

Whichever method of distribution is employed, education of distributors and users is integral to the success and sustainability of ceramic water filter technology.
Key issues to consider in distribution strategies are:

  1. ensure appropriate training and education material is provided to the distributor in the short and long term so that they are capable of explaining the operation and maintenance requirements, and answering questions about the filter;
  2. the distributor needs access to educational and instructional material to provide to the  end user to ensure correct maintenance is conducted in the long term;
  3. an ongoing connection between the distributor and the community is important – such a role would provide an ongoing access point for questions and replacement supplies.  Additionally, a long term presence of the filters in a community would continue to reinforce the value of filters and remind people about the opportunity to access replacement parts or a later opportunity to buy a filter.

Ceramic water filters are not a passive resource, they require ongoing management and maintenance by users. Therefore, like computer systems in any country, an ‘after sales support’ is essential for ongoing and appropriate use of ceramic water filters.

Technical Drawing


The Handbook incorporates technical drawings of key items of machinery and facilities used to assist as anyone considering setting up a ceramic water filter factory.  Including the kiln, clay mixer, hydraulic press, drying racks.

Drawings for the clay mixer and hydraulic press are currently under review and will be added to the site once finalised.



The Handbook incorporates a range of technical appendices detailing microbiological tests, RDIC’s factory layout, instructions on building a kiln, and sample education materials all provided to ensure the Handbook is a sound resource for new parties.

Instructional brochures provided to community members are currently under review at RDIC and will be provided on the web when complete.

The Handbook is designed to be complemented by Instructional Videos that go through the manufacture process.


  1. Brown, J. and Sobsey, M, 2006, Independent Appraisal of Ceramic Water Filtration Interventions in Cambodia: Final Report – Submitted to UNICEF 5 May 2006.
  2. Brown, J.M, 2007. Effectiveness of Ceramic Filtration for Drinking Water Treatment in Cambodia. Dissertation, (PhD.) University of North Carolina – Chapel Hill.
  3. Lantagne, D.S. 2001 (a). Investigation of the Potters for Peace Colloidal Silver Impregnated Ceramic Filter – Report 1: Intrinsic Effectiveness.  Submitted to Jubilee House Community.  http://www.edc-cu.org/pdf/report1-final.pdf *
  4. Lantagne, D.S. 2001 (b).  Investigation of the Potters for Peace Colloidal Silver Impregnated Ceramic Filter – Report 2: Field Investigations.  Submitted to Jubilee House Community.  http://pottersforpeace.org/wp-content/uploads/alethia-report-2.pdf

Frequently Asked Questions

Question: So, why does this work?  How are germs killed in this ceramic pot?
Answer: Two processes are at work. Because the mixture of rice and clay produce small micro pores, parasites, amoebas, and large bacteria cannot flow through due to mechanical processes. Simply put, water can fit through the pores, most disease causing organisms cannot.  The coating of colloidal silver adds a chemical process to stop other bacteria. Together, this system eliminates 98% of the harmful diseases present in surface water.

Question: How long does this filter last?
Answer:  A study was done at MIT that showed that the filter maintained its effectiveness for over one year, however testing was stopped after one year.  It is estimated that the filter will last with repeated daily use long after one year.

Question: How does the ceramic pot become so porous?
Answer:  Ceramics are inherently porous.  However, our specialized process of firing the clay and rice husk mixture causes the rice husks to completely burn away in the intense heat of the kiln.  When the rice husks burn out of the mixture, micro pores remain in the newly created ceramic filter which allow for a perfect seepage of water minus the harmful microbes that once infected it.

Question: What maintenance does the ceramic filter require?
Answer: If the water is turbid or cloudy or has a lot of solids in it then it needs to be periodically cleaned with a soft bristle brush.  RDI recommends a monthly cleaning unless visual buildup of solids is identified.  Solids such as leaves or other biomass from a highly contaminated source should be cleaned more frequently.

Question:  How do you know that it works in the village?  Do families really use this?
Answer: Part of the commitment RDI has for maintaining a its community focus for sustainable change is to insure the viability of the filters.  The filters are tracked, and periodically RDI goes back to the community and runs tests on the filters to verify that the filters are still giving families safe, pure drinking water.   Projects at RDI are ONGOING, we cherish the opportunity to impact the lives of families.  If something is working, we test it later to make sure it is still working.  If a project is NOT working we look for new solutions.