Pure Bushcraft Outdoor Skills Challenge 84: Compare Two Water Filters

When you’re outdoors, having a reliable way to obtain safe drinking water is an important part of preparation. Portable water filters can make collecting water more practical, but different models vary in their design, flow rate, capacity and intended use.

In this challenge, you’ll compare two water filters by passing the same source water through each one and recording the results. Rather than relying on packaging claims or appearances, you’ll carry out a simple, controlled test to see how the filters perform under the same conditions.

This is a practical equipment assessment, not a test of whether the resulting water is safe to drink. Clear water is not necessarily safe water, and filtration alone does not remove every possible contaminant.

Your Challenge

Use two suitable outdoor water filters to process separate, equal portions of the same prepared test water. Record how long each takes, compare the results and identify the differences that matter when choosing equipment for outdoor use.

Ideally, use two filters designed for comparable purposes, such as portable filters intended for treating water collected during hiking or camping. Read the instructions for both products before starting, as their operating methods and limitations may differ.

Your aim is to assess measurable performance rather than simply decide which filter looks better. You should consider flow rate, ease of use, handling, cleaning requirements and the manufacturer’s stated protection against contaminants.

Important: Do not drink the test water or either filter’s output. This challenge is about comparing equipment, not establishing that water is microbiologically or chemically safe.

What You’ll Need

• Two outdoor water filters suitable for the same general purpose.
• A clean container for preparing and mixing the test water.
• Two clean collection containers of the same size.
• A measuring jug or another way to measure equal volumes.
• A stopwatch or phone timer.
• A notebook or spreadsheet to record your observations.
• A stable work surface.

Use clean tap water for a straightforward comparison. If you want to assess how the filters handle visible suspended particles, use a commercially prepared, non-hazardous test suspension only if both manufacturers’ instructions permit it. Do not use sewage, stagnant water, floodwater, chemically contaminated water or water containing unknown substances.

Avoid adding soil, chemicals or biological material to create an artificial test mixture. Such additions can damage equipment, expose you to hazards or produce misleading results.

If one filter requires a separate bottle, hose or pump, use the correct components supplied or approved by its manufacturer.

Take the Challenge

1. Read the instructions for both filters

Before you begin, inspect each filter and read its operating instructions carefully.

Identify how each one works. Some filters use gravity, some require pumping, and others attach directly to a compatible bottle or hydration system. The procedure for operating one model may not be appropriate for another.

Look for the manufacturer’s information on:

• The contaminants the filter is designed to reduce or remove.
• Its stated filtration performance and limitations.
• The expected flow rate, if published.
• Its rated service life or capacity.
• Cleaning, backflushing and maintenance requirements.
• Any restrictions on the types of water it can treat.

Pay particular attention to whether the products are genuinely comparable. A filter designed mainly to improve taste may not offer the same protection as one designed to remove particular microorganisms.

A filter’s advertised pore size or filtration rating should not be treated as proof that it removes every pathogen. Viruses, dissolved chemicals and other contaminants may require different treatment methods.

Write down the model names and the manufacturer’s intended uses. This will help you interpret the results later.

2. Prepare the test area

Place both filters on a stable surface where you can operate them without spilling water or damaging their components.

Label your collection containers Filter A and Filter B. Make sure they are clean and large enough to collect the volume you intend to process.

Check that the containers cannot tip over and that any hoses, fittings or connections are properly secured.

If you are using a filter that requires pumping or squeezing, position it so that you can operate it comfortably and consistently. If one is gravity-fed, ensure it can be suspended or positioned according to the manufacturer’s instructions.

Keep the test water and collected output clearly separated from drinking water, food and clean hydration equipment.

3. Prepare equal portions of the same water

Measure out two equal portions of your chosen test water from the same thoroughly mixed batch.

For example, you might use 500 millilitres for each filter, provided that volume is suitable for both products and their instructions allow it.

Using water from the same batch reduces the chance that differences in the starting water will influence your observations.

If you are testing the filters’ flow rates using ordinary tap water, the results will primarily demonstrate how quickly each system processes that water under your chosen conditions. They will not necessarily predict performance with naturally collected water, which can contain particles that slow a filter or clog its media.

Prepare each filter according to its instructions. Some products require soaking, flushing or an initial conditioning process before use. Complete those steps first, and record them if they affect the comparison.

Do not deliberately skip preparation requirements to make one filter appear faster than the other.

4. Filter the first portion

Set up Filter A according to the manufacturer’s instructions.

Start your timer when you begin the defined filtering process. For a pump filter, this might be when you start pumping. For a gravity filter, decide whether you are measuring from the moment water begins entering the system or from another clearly defined point.

Use the same timing method for both filters.

Collect the output in the labelled container and stop the timer when you have collected your chosen volume. Record the time and any observations about the process.

Notice whether the filter is easy to prime, whether it requires sustained effort, whether the connections remain secure and whether the flow stays consistent.

If the filter slows or stops, follow the manufacturer’s troubleshooting guidance. Do not force water through it or dismantle a pressurised system.

Keep the output clearly labelled as test water and do not drink it.

5. Repeat the test with Filter B

Prepare Filter B as instructed by its manufacturer and process the second equal portion.

Use the same target volume and the same timing method that you used for Filter A.

If Filter A required a preliminary flushing step, determine whether Filter B has a similar requirement and follow its own instructions. Record any differences in preparation time separately from the actual filtering time.

Observe how the second filter behaves. Does it produce a steady flow? Does it require more physical effort? Is it straightforward to connect and operate?

Try to keep the test conditions as similar as reasonably possible, including the starting volume, collection method and operator technique.

Do not alter the manufacturer’s recommended operating procedure simply to make the two systems behave identically. Your aim is a fair comparison of each filter when used correctly.

6. Calculate and compare the results

Once both tests are complete, compare the recorded times.

If you collected the same volume with each filter, the one that completed the test in less time had the higher observed flow rate under those particular conditions.

You can calculate an approximate flow rate using this formula:

Flow rate = volume filtered ÷ time taken

For example, if a filter processes 500 millilitres in 100 seconds, its observed flow rate is 5 millilitres per second, equivalent to 300 millilitres per minute.

These figures are illustrative only. Use your own measurements for the challenge.

Remember that the observed rate is not necessarily the manufacturer’s rated flow rate. Differences in filter condition, water temperature, pressure, pumping technique and setup can affect the result.

If you want a more reliable comparison, repeat each test using fresh equal portions of the same prepared water. Follow any limits on continuous operation, flushing and maintenance stated by the manufacturers.

Record the results in a table:

Measurement	Filter A	Filter B
Model	Record yours	Record yours
Test volume	Your measurement	Same volume
Filtering time	Your result	Your result
Observed flow rate	Calculate yours	Calculate yours
Ease of operation	Your observations	Your observations
Cleaning requirements	Manufacturer’s instructions	Manufacturer’s instructions
Main advantages	Your assessment	Your assessment
Main limitations	Your assessment	Your assessment

7. Compare more than speed

A faster filter is not automatically the better choice for outdoor use.

Consider how the equipment would suit the activities you actually undertake. A filter that works well for one person on a day walk may be inconvenient for a group that needs to process larger quantities of water.

Weight and packed size may matter to someone travelling on foot. Ease of operation could be more important for someone who finds prolonged pumping difficult. A filter that can be maintained in the field may offer practical advantages on longer trips.

Consider the following questions:

• Which filter was easier to set up?
• Which required less effort to operate?
• Was the flow rate consistent?
• Did either filter require more preparation?
• How easy would each be to clean or maintain?
• What are their stated service lives and replacement requirements?
• Which contaminants does each manufacturer say it can address?
• Are there conditions in which either filter must not be used?

Use the manufacturers’ published specifications to answer questions that a simple flow test cannot resolve. You cannot determine microbiological safety by looking at filtered water, and a comparison of flow rates does not establish which filter removes more pathogens.

8. Clean up and store the equipment

When you have finished, dispose of the test water appropriately and clean the work area.

Follow the manufacturer’s guidance for cleaning, drying, backflushing and storing each filter. Do not assume that the same maintenance procedure is suitable for both products.

Keep untreated test water away from clean drinking-water containers and equipment. Wash your hands after handling the equipment and any test water that was not ordinary tap water.

If the test involved a prepared suspension, follow its specific disposal instructions.

Finally, check that all components are accounted for and that the filters are stored as recommended. Record any maintenance needed before they are used on a real trip.

Check Your Results

Review your notes and answer these questions:

1. Did you use two filters intended for comparable purposes?
2. Did both filters process equal volumes from the same prepared batch?
3. Did you follow each manufacturer’s operating instructions?
4. Which filter had the higher observed flow rate?
5. Which was easier to set up and operate?
6. Did either filter require additional preparation or maintenance?
7. What are the main limitations of each product?
8. What further information would you need before relying on either filter during an outdoor trip?

If the results were unexpected, check your measurements, timing method and setup. A single test is useful for learning, but it does not provide a complete assessment of long-term performance.

Remember that a filter’s effectiveness depends on what it is designed to remove. Some outdoor filters do not remove viruses, dissolved chemicals or other contaminants, and a clear appearance is not proof of safe drinking water.

For real outdoor use, choose a treatment method appropriate to the water source and follow reliable public-health guidance alongside the manufacturer’s instructions. Where necessary, filtration may need to be combined with an appropriate disinfection method.

Complete the Challenge

To complete this challenge, test two suitable outdoor water filters using equal portions of the same prepared water, record their filtering times and calculate their observed flow rates.

Compare their ease of use, maintenance requirements, intended applications and limitations. Your final assessment should explain which filter you would prefer for a particular outdoor activity and why, based on the evidence you collected.

You do not need to buy two new filters. If you already own two suitable models, use those. If you only have one, you can complete the challenge when you have access to a second suitable filter.

Do not drink the test water or use this experiment as proof that either filter produces safe drinking water.

How to Submit Your Challenge

Submit your evidence

Take a clear photograph of both filters alongside your labelled collection containers and recorded results. You can include your comparison table in the photograph or attach a photograph of your written notes.

Your evidence should demonstrate that you carried out the comparison yourself. Do not photograph yourself drinking the test water or imply that visual clarity proves it is safe.

To submit your challenge:

1. Go to your Pure Bushcraft member profile.
2. Open Social Activity.
3. Upload your photograph of the two filters and your results.
4. Add the hashtag #Pure BushcraftChallenge84 to your post.
5. Share it for verification.

If you wish, include the observed flow rates and one sentence explaining which filter you preferred for your chosen activity.

Challenge 84 Checklist

Want to Push Yourself?

Repeat the comparison on another day, using the same test method, and see whether your results are consistent. If the manufacturers permit repeated testing under your chosen conditions, compare the average filtering times rather than relying on a single reading.

You could also compare the packed weights and dimensions of the two systems, including their normal accessories. Add these figures to your assessment and consider how they might influence your choice for a short walk, a multi-day hike or a group expedition.

For an additional research task, compare the manufacturers’ stated contaminant-removal capabilities and maintenance requirements. Make a clear distinction between what you measured yourself and what the manufacturer claims.

The most useful outcome is not simply choosing the fastest filter. It is learning how to evaluate outdoor equipment systematically, recognise the limitations of a basic test and select tools appropriate to the conditions in which you intend to use them.

What’s Next?

Continue building your practical outdoor skills with Pure Bushcraft Outdoor Skills Challenge 83: Camp in Your Garden for a Night. This challenge gives you an opportunity to practise setting up camp, organising your equipment and preparing for an overnight stay before relying on your kit farther from home.

Pure Bushcraft Outdoor Skills Challenges can be completed in any order, so you can explore whichever skills interest you most and return to earlier challenges whenever you want more practice.

Once you’ve shared your evidence and it has been verified, the Pure Bushcraft Outdoor Skills Challenge 84 is complete and the completed challenges figure will be updated on your profile.