Choosing an Emergency Water Purification System

When choosing an emergency water purification system there are many factors you should consider. This guide will help you make an informed decision.

Water Purification Systems (WPS) are used by many types of organization to ensure the provision of clean water when other means are unavailable due to disaster or other failure.

Here is a list of the groups that might want to use an emergency WPS:

There are many water purification systems available on today's market. They differ in may respects, including capacity, size, weight, and price. A system that works well for one type of organization may not necessarily be the right choice for yours.

The following questions will help focus your search on a WPS right for your needs:

How much water will you need?

Most water purification systems are rated according to how much water they can treat on an hourly or daily basis. Typically, smaller systems are rated in terms of gallons or litres per hour (GPH/LPH) and the larger systems are rated in terms of gallons or litres per day (GPD/LPD).

According to The SPHERE Handbook, there is a minimum standard for the amount of water each disaster victim needs each day for the purposes of drinking, cooking, and personal hygiene. SPHERE and organizations such as the World Health Organization (WHO) have recommended 7.5 - 15 litres water (2 - 4 gallons) per person per day for basic survival, cooking and health needs.

Based on this amount, you can calculate the required capacity for your WPS. For example, if you need to serve the basic requirements of 3,000 people, you should narrow your search to a WPS capable of producing 45,000 litres potable water each day (3,000 x 15 = 45,000).

This example represents a "best-worst" case scenario. In actual fact, you could serve 6,000 people with a minimal survival level of 7.5 litres per person per day.

A hospital will have very different needs to that of an individual due to requirements for laundry, facilities cleaning, toilets, etc. The WHO recommends a minimum of 40 - 60 litres per in-patient per day. A system able to produce 45,000 litres water per day could serve 750 patients (45,000 / 60 = 750).

Of course, these example are theoretical, and results will vary depending on factors such as available power source, filter media, storage and distribution capacities, maintenance, human resources, etc.

What type of water will you be treating?

Water purification systems are usually classified according to the type of water they can treat. This usually falls into the following types:

  • Fresh water - usually streams, rivers, lakes, ponds, wells, etc.
  • Brackish water - a mixture of mostly fresh water plus salt water, usually found is estuaries.
  • Salt water - from seas and oceans.

Fresh water (water with low concentrations of dissolved solids) is typically easier and less expensive to purify than other sources of water. Fresh water can be made potable by passing it through a series of filters to remove sediment, bacteria, viruses, protozoan cysts, and most color and odor issues.

Systems designed to treat brackish and salt water use a technology called Reverse Osmosis (RO) which is considered the only effective way of making salt water fit to drink. This process works by using pressure (50-60 psi) to force water with a high salt content through a semi-permeable membrane to where the water is free of the salt molecules.

If you know that you will be treating brackish or salt water, a system employing reverse osmosis technology would be the logical choice.

How portable does the system need to be?

Consider where your WPS will be deployed. What are the routes the system will take before it arrives at it final destination?

  • What type of transportation will be used? Consider how the system will be carried by air, across water, and by road.
  • Does the system packaging have skids for fork-lifts?
  • How will the system be delivered if the roads are flooded or washed out? Typically, your WPS will be needed where existing infrastructure is broken and difficult to navigate.
  • Will the packaged system fit through doorways and other openings? For example, will it need to fit through the cargo door of a Piper 31 aircraft (25" x 43")?
  • What are the size and weight restrictions? Consider the additional costs and paperwork requirements to transport the system.
  • What supporting infrastructure is needed to take delivery of the system? Consider how many people, vehicles, forklifts, pallet jacks or trailers will be needed.
  • Where will the system be stored and who will look after it? Consider what security will be needed to protect your valuable asset.
  • Would it be more practical to use multiple smaller units than one larger system?

How will the system be powered?

Unless you have a gravity-fed WPS, you will need to pump the untreated water from its source into the system. You have a number of choices:

  • Manually operated. A manually operated system (such as a hand-pump) will clearly demand a lot of effort to keep it running and will limit the throughput of the system.
  • Gas / petrol engine. A gas/petrol powered system will require that fuel is readily available. A safe assumption is that if it took a gas-powered vehicle to deliver the system to the response site, then it's equally likely that a supply of fuel can be made available to power the equipment. Gas-powered equipment has the advantage of night and day operation, despite the disadvantage of noise.
  • Battery power. Battery powered equipment may place a limit on the volume of water that can be pumped and processed due to the battery-powered pumps available on the market. Battery power has the advantages of 24-hour, silent operation.
  • Solar power. Solar power is relatively efficient and readily available, but has the drawback of only working when there is sufficient sunlight.
  • Hybrid. A hybrid solution may work well, for example using a gas water pump and battery operated UV lamps.

Your choice of how to power your water purification system will depend of the particular situation and circumstances. You may also want to consider how the WPS equipment can assist other aspects of your relief effort, e.g. providing power to light to a clinic, recharge radio equipment and cell phones, or to provide assistance with flood remediation.

How will the treated water be stored and distributed?

The process of making the water fit to drink is only part of the solution. As part of your decision-making, you should consider how the water will be stored and distributed.

The purified water will need to be stored if it's not going to be consumed immediately. Have you considered a rigid storage tank or collapsible bladder? The advantage of using a smaller-capacity WPS in conjunction with a means to store the clean water is that it can be produced during off-peak hours and distributed when the demand is greater.

If you are assisting people across a wide geographic area, would it make more sense to employ several smaller water purification units rather than a single larger unit with a vehicle capable of transporting the water to where it needs to go? Water is very heavy and difficult to transport. The added step of transporting the clean water may also introduce a risk of recontamination which should be avoided.

How will the end-users collect and store their water? Consider the use of mobile tap-stands and hoses. Consider the provision of collapsible containers for people to collect and store water safely in their homes.

Who will be operating the system?

A system with a complicated multi-step operations manual may make it difficult to train local operators quickly and effectively. As a rule, the simpler the better. By using system components that people are familiar with, you are reducing their learning curve. For example, is the make and model of the water pump and electric generator familiar to your overseas colleagues?

Other aspects to consider are:

  • Does your system use familiar units (i.e. gallons vs. litres)?
  • Can the basics of the system be taught in a relatively short time?
  • Is the system forgiving and fault-tolerant?
  • Does the system warn when a component needs replacement or repair?
  • Does the system include a basic repair tool kit and spare parts?
  • Does the system come with a comprehensive instruction manual?
  • Does the vendor provide adequate product support?

How will the system be maintained?

A water purification system can be a complex piece of equipment that will require careful maintenance if it is to provide useful ongoing service. Each part of the WPS will require its own level of attention.

Here are just a few of the things you should be mindful of when considering how your WPS will be maintained:

  • Gas / petrol pumps and generators:
    • Empty fuel before transporting and storage
    • Check and change spark plugs
    • Check and change oil levels
    • Store upright and according to manufacturers instructions
  • Electrical equipment:
    • Keep free from moisture and risk of shock
    • Test on a regular basis
  • Filters and housings:
    • Replace or clean when their performance has diminished
    • Replace O-rings and re-apply silicone grease as needed
    • Replace UV light every year
    • Flush system with disinfectant
    • Who will order replacement filters and how often?


A mobile water purification system may be one of the most important pieces of equipment you purchase so you need to know it will perform well in the field, produce life-saving water and live up to its claims.

  1. Make sure the system can generate the amount of potable water you need from the source of contaminated water your most likely to encounter.
  2. Make sure the system can be transported as easily as possible without creating new problems on the way.
  3. Consider how the system will be powered.
  4. Consider your water storage and distribution needs.
  5. Consider how the system will be operated, maintained, and supported.

Please contact us if you have further questions. We're always happy to help.