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Travel health · bottle selector

Choose the bottle that fits the water.

Tell us what you are doing, where the water comes from and what you want to avoid. The selector ranks practical options, explains the match and tells you what the bottle cannot do.

Start the selector
01

Your trip

What are you doing?

City break, overland journey, trek or carry-on-only trip.

02

Your risks

What should it address?

Microbes, metals, chlorine, odour or sediment.

03

Your result

Why this bottle?

A ranked match with reasons, limits and a safer fallback.

Interactive decision guide

Build your recommendation

Start with the likely source, not the bottle you already like. Your result updates as you choose.

1 What sort of trip are you taking?
2 What water are you likely to use?
3 What do you want the bottle to address?

Choose everything relevant. Product claims vary: “selected heavy metals” never means every metal in every source.

4 What matters most after safety?

Your recommendation

Best matches for your trip

Read only what you need

The safety notes behind the selector

Filter, purifier and UV are different

Taste filters improve already treated water. Microbiological filters usually block bacteria and protozoa but not viruses. Purifiers are designed for bacteria, protozoa and viruses. UV can inactivate microbes in clear water but removes no sediment, chemicals, metals or salt.

A bottle is only one layer

Wash with soap before eating, choose freshly cooked food served hot, peel fruit yourself where water is uncertain, and treat ice as water. Safe drinking water cannot prevent illness from contaminated food or hands.

How to use a purifier safely
  1. Practise before the trip and activate the cartridge exactly as directed.
  2. Use the clearest available freshwater; settle or prefilter cloudy water.
  3. Keep dirty surfaces away from the clean mouthpiece and wipe bottle threads.
  4. Add drink powders only after treatment unless the manufacturer permits otherwise.
  5. Replace cartridges on time and carry a backup method on remote trips.
If you develop diarrhoea

Replace fluids and electrolytes using sealed, boiled or properly treated water. Seek medical advice promptly for blood in the stool, fever, severe pain, repeated vomiting, dehydration, incapacitating illness or symptoms that persist. Get early advice for children, older people, pregnancy or significant medical conditions.

Evidence and limits

Sources used by the selector

Independent health guidance

Product claims

General information, not personal medical advice. Last reviewed: July 2026.

Contents

Pathogen and product guide

Pathogen and product guide

Practical examples of the difference between protozoa, viruses and bacteria when choosing a bottle for travel

A travel bottle may be called a filter, purifier or UV bottle, but those words do not mean the same thing.

The simplest way to understand the difference is:

Bacteria

Bacteria are living microorganisms. They include E. coli and the bacterium that causes cholera.

Common sources

Common sources include sewage-contaminated food or water, undercooked food, unsafe dairy, dirty hands, wells and poorly maintained storage tanks.

Viruses

Viruses are much smaller. They can pass through many ordinary hiking filters.

Common sources

Common sources include sewage-contaminated water, food handled by an infected person, shellfish, ice and shared surfaces.

Protozoa

Protozoa are microscopic parasites. They include Giardia and Cryptosporidium.

Common sources

Common sources include untreated rivers and lakes, contaminated wells, human or animal faeces, and water affected by flooding or inadequate sanitation.

A product that deals with one group does not automatically deal with the other two.

Clear water can contain all three. Water may look normal even when sewage has entered a pipe, a rooftop tank has not been cleaned, or a well has been contaminated after flooding.

The question to ask is:

Has this exact product been tested or credibly claimed to treat bacteria, viruses and protozoa under the conditions in which I will use it?

Filter bottles, purifier bottles and UV devices

Filter bottles

Filter bottles use a physical barrier to strain contaminants from water. Many block larger organisms such as bacteria and protozoa but do not remove much smaller viruses. A taste filter is narrower still: for example, the LARQ PureVis 2 straw targets chlorine, VOCs and specified metals rather than acting as a broad microbial filter.

Purifier bottles

Purifier bottles address bacteria and protozoa plus viruses, using suitable media, chemicals or another tested process. GRAYL GeoPress and Water-to-Go 75cl Eco Active are integrated purifier-bottle examples.

UV devices

UV devices do not strain anything out. They deliver ultraviolet light that inactivates bacteria, viruses and protozoa when the water is clear and the complete treatment is performed correctly. SteriPEN is a dedicated handheld UV purifier used in a separate open container.

The five products in one table

Comparison of five travel water-treatment products against bacteria, viruses and protozoa
Product Bacteria Viruses Protozoa What it actually does Best use
GRAYL GeoPress Yes Yes Yes Presses water through a purifier cartridge that removes pathogens and also reduces sediment, bad taste and some specified chemicals and metals. The strongest all-round one-bottle option for uncertain freshwater when weight is less important.
Water-to-Go 75cl Eco Active Yes Yes Yes Draws water through a three-in-one purifier cartridge that combines mechanical filtration, activated carbon and electropositive media. Lightweight travel where protection, capacity and value matter more than pourable treated water.
SteriPEN Ultra Yes Yes Yes Uses a validated UV treatment cycle to inactivate microorganisms in clear water. It removes nothing from the water. Clear but microbiologically uncertain tap, well or freshwater when low weight matters and charging is reliable.
SteriPEN UltraLight Yes Yes Yes Uses the same UV-C treatment principle in a smaller, lighter rechargeable unit for clear water. It removes nothing from the water. Ultralight travel with a compatible open container and a simple backup treatment method.
LARQ Bottle PureVis™ 2 Selected bacteria tested No equivalent broad public claim identified No equivalent broad public claim identified Uses UV-C for self-cleaning and publishes results for selected bacteria. Its straw filter targets taste and specified chemical contaminants rather than providing broad microbial filtration. Already treated municipal water where design, insulation, taste and everyday convenience matter.

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The table reflects the manufacturers’ current published claims. It is not a guarantee for every water source or every possible contaminant.

A useful correction about UV

It is easy to assume that protozoa must be the hardest organisms for UV to treat because they have protective cysts or oocysts. That assumption is wrong.

Appropriately delivered UV can be very effective against Giardia and Cryptosporidium. US EPA technical guidance describes viruses as generally the most resistant of the three groups to UV, followed by bacteria, with Giardia cysts and Cryptosporidium oocysts generally more UV-sensitive.

The important difference between UV products is therefore not simply the wavelength printed in the marketing material. What matters is:

  • the UV dose delivered through the whole treatment cycle;
  • whether the product has suitable testing for the organisms concerned;
  • whether the water is clear enough for UV to pass through it;
  • whether the treatment is completed correctly;
  • whether the battery is adequately charged.

This is why the SteriPEN and LARQ should not be treated as equivalent merely because both use UV-C.

Bacteria: the most common everyday cause of travellers’ diarrhoea

Bacteria are living, single-celled microorganisms. Disease-causing bacteria can reach water through:

  • sewage leaks;
  • cracked or depressurised pipes;
  • poorly protected wells;
  • dirty rooftop or underground tanks;
  • flooding;
  • contaminated containers;
  • handling after treatment.

Examples include:

  • enterotoxigenic E. coli, a common cause of travellers’ diarrhoea;
  • Shigella;
  • Salmonella;
  • Vibrio cholerae.

Cholera is a bacterial disease. It is not caused by a virus or protozoan parasite.

Boiling, correctly applied chemical disinfection, adequate UV and filters or purifiers designed for bacteria can all work. A basic activated-carbon taste filter should not be assumed to remove bacteria.

Viruses: tiny enough to pass through many ordinary filters

Viruses are extremely small infectious particles. Waterborne examples include:

  • norovirus;
  • rotavirus;
  • hepatitis A virus.

They usually enter drinking water through human faecal contamination. This makes virus protection particularly relevant where sewage may enter a water source or distribution system.

Many lightweight hiking filters are designed to block bacteria and protozoa but do not claim virus removal. Their pores or filtration mechanisms may not stop particles as small as viruses.

Viruses can be addressed by boiling, suitable chemical disinfection, adequately validated UV or a purifier that specifically claims virus removal.

Protozoa: larger parasites that can survive routine chlorination

Protozoa are microscopic, single-celled parasites. Important drinking-water examples include:

  • Giardia duodenalis, which causes giardiasis;
  • Cryptosporidium species;
  • Cyclospora cayetanensis;
  • less commonly in travellers, Entamoeba histolytica.

Giardia and Cryptosporidium leave the body in protective forms called cysts and oocysts. These can enter water through:

  • human sewage;
  • livestock and other animal faeces;
  • unprotected wells;
  • contaminated groundwater;
  • cracked pipes;
  • dirty tanks;
  • water trucks;
  • flooding;
  • irrigation or washing water used on uncooked produce.

Cryptosporidium is particularly resistant to the chlorine concentrations commonly used in drinking-water treatment. Giardia cysts are also relatively chlorine-resistant.

That does not mean they are resistant to properly delivered UV. Adequately validated UV can inactivate both.

GRAYL, Water-to-Go, SteriPEN and LARQ: the practical difference

Purifier bottle

GRAYL GeoPress: removes pathogens and improves the water

The GeoPress is the broadest one-device option discussed here.

You fill its outer cup and press the inner bottle through the purifier cartridge. GRAYL states that the cartridge removes:

  • 99.9999% of bacteria;
  • 99.99% of viruses;
  • 99.9% of protozoan cysts.

It also filters sediment, microplastics, bad taste and odour, and reduces specified chemicals and metals.

This makes it the most reassuring choice when the water is clear enough to use but its treatment, pipes or storage are genuinely uncertain.

Its disadvantages are weight, bulk, cartridge cost and the effort required to press it. The GeoPress weighs about 450 g empty, and pressing normally becomes harder as the cartridge reaches the end of its useful life.

Think of it as: a purifier that physically takes unwanted material out of the water.

Purifier bottle

Water-to-Go 75cl Eco Active: a lightweight integrated purifier bottle

You fill the bottle and drink through its three-in-one filter cartridge. Water-to-Go says the cartridge combines mechanical filtration, activated carbon and an electropositive medium to address bacteria, viruses, protozoa, microplastics and selected chemicals.

At about 138 g with a 750 ml capacity, it is substantially lighter than a GeoPress. The trade-off is that treated water is drawn through the filter as you drink, so it is less convenient for sharing, filling another container or brushing your teeth. A new or dried cartridge must be activated correctly, and the cartridge must be replaced on schedule.

Think of it as: a lightweight purifier bottle for travellers who value low weight and capacity over pourable treated water.

UV device

SteriPEN Ultra or UltraLight: treats microbes but removes nothing

A SteriPEN is a UV purifier rather than a filter.

Place the UV lamp into a compatible open container and stir the clear water for the complete treatment cycle. Katadyn states that the SteriPEN Ultra eliminates bacteria, viruses and protozoa and treats:

  • 0.5 litre in about 48 seconds;
  • 1 litre in about 90 seconds.

The Ultra is USB rechargeable. The UltraLight is smaller and lighter and is also rechargeable.

A SteriPEN is especially attractive for travel because it is far lighter than a GeoPress and can treat water in different compatible containers.

However, it:

  • requires clear water;
  • relies on a charged battery;
  • does not remove sediment;
  • does not remove metals or chemicals;
  • does not improve unpleasant taste or odour;
  • does not automatically clean contaminated bottle threads or the outside drinking surface.

Think of it as: a light, fast microbial treatment tool for clear water.

Filter bottle

LARQ Bottle PureVis™ 2: best understood as an urban lifestyle bottle

The LARQ combines:

  • an insulated bottle;
  • automatic UV-C self-cleaning;
  • hydration tracking;
  • a removable filter straw.

LARQ publishes strong results for selected bacterial tests. Its current official page states up to:

  • 99.999% elimination of Salmonella in a 60-second cycle;
  • 99.99% elimination of E. coli in a 60-second cycle.

Its Essential Bottle Filter targets chlorine, pharmaceuticals and PFOA/PFOS. Those are chemical and aesthetic filtration claims, not broad bacteria-virus-protozoa filtration claims.

The official product evidence does not present the same all-three-pathogen coverage as the GeoPress or SteriPEN. For that reason, the PureVis 2 is better suited to generally treated municipal water than to being the sole treatment for genuinely uncertain water in a high-risk setting.

Think of it as: a premium insulated bottle that helps keep already reasonable water and the bottle fresher.

Country examples

These examples do not mean that every tap or hotel in a country has the same risk. Water quality can vary by city, neighbourhood, season, building, treatment plant, tank and pipe network.

· India ·

India: a hotel tap supplied through an uncertain rooftop tank

India has directly documented Giardia and Cryptosporidium concerns, although risk varies enormously.

One rural groundwater study modelled a mean daily Giardia-or-Cryptosporidium infection risk of approximately 0.06% to 1.53% under its study scenarios. This should not be presented as the risk for every traveller or every glass of Indian tap water. It applies to particular rural groundwater data and modelling assumptions.

A modern hotel may receive treated municipal water, but the water can then pass through a building tank or intermittent pipe system.

Practical example: The water is clear, but you cannot verify the hotel tank or distribution system.

  • GRAYL GeoPress: strongest all-round option because it covers bacteria, viruses and protozoa and also filters the water.
  • Water-to-Go: a lighter purifier-bottle alternative when drinking through the filter is practical.
  • SteriPEN: a strong lightweight alternative when the water is genuinely clear and you can complete the treatment correctly.
  • LARQ: not the preferred sole treatment because its published evidence is narrower.

· South Sudan ·

South Sudan: clear borehole or trucked water

Reliable national measurements for Giardia, Cryptosporidium and waterborne viruses are limited. A precise national prevalence would therefore be misleading.

The concern is based on practical conditions documented by WHO and UNICEF, including weak access to safe water and sanitation in many areas, displacement, flooding, cholera outbreaks and water transported or stored through multiple stages.

Clear water could be contaminated:

  • at the borehole;
  • during pumping;
  • in a truck;
  • in a storage tank;
  • while being transferred into smaller containers.

Practical example: The water looks clear, but its treatment and storage history are unknown.

  • GRAYL GeoPress: the conservative all-round choice because it does not rely on electricity and covers all three microbial groups.
  • Water-to-Go: a much lighter no-battery alternative, provided the source is suitable for the cartridge and the filter has been prepared correctly.
  • SteriPEN: useful when the source is clear and charging is reliable, but it cannot remove sediment, fuel, metals or other chemicals.
  • LARQ: not the preferred sole purifier for this scenario.

Do not use any of these ordinary travel devices for water affected by fuel, salt, mining waste, industrial pollution or obvious sewage.

· Haiti ·

Haiti: clear guesthouse water, ice and salad

Haiti illustrates why focusing on only one pathogen group can be misleading.

Cholera, which has caused major outbreaks in Haiti, is bacterial. Historical studies have also detected Cryptosporidium in selected water sources, and the CDC identifies Haiti as a recognised geographic risk for Cyclospora.

Cyclospora can be transmitted through contaminated produce as well as water.

Practical example: You purify your drinking water but eat a salad washed with untreated water.

  • GRAYL, Water-to-Go or SteriPEN: can reduce the microbial risk from the water you personally treat.
  • None of these devices: can reverse contamination already present on salad, herbs, cut fruit, ice, utensils or hands.
  • LARQ: remains better suited to water that is already reasonably treated.

Which one should the traveller choose?

Choose GRAYL GeoPress when:

  • you want the strongest all-round one-bottle protection;
  • viruses are a realistic concern;
  • water may contain sediment or taste unpleasant;
  • you want to pour treated water into another container;
  • you prefer not to rely on a battery;
  • carrying about 450 g is acceptable.

Choose Water-to-Go 75cl Eco Active when:

  • you want protection against bacteria, viruses and protozoa at low pack weight;
  • 750 ml capacity and lower running cost matter;
  • drinking through the filter suits your trip;
  • you do not need to pour treated water for another person;
  • you can activate and maintain the cartridge correctly;
  • you prefer not to rely on a battery.

Choose SteriPEN Ultra or UltraLight when:

  • the water is clear but microbiologically uncertain;
  • bacteria, viruses and protozoa all matter;
  • low weight matters more than removing sediment or chemicals;
  • you can reliably charge the device;
  • you have a compatible open container;
  • you are willing to carry a simple backup treatment method.

Choose LARQ PureVis 2 when:

  • the water is already treated municipal water;
  • your main concerns are bottle cleanliness, taste, chlorine and specified chemical contaminants;
  • insulation, appearance and hydration tracking matter;
  • you are not relying on it as your only purifier for high-risk untreated water.

The shortest possible answer

  • GRAYL GeoPress: removes bacteria, viruses and protozoa and also filters the water.
  • Water-to-Go 75cl Eco Active: filters bacteria, viruses and protozoa in a much lighter drink-through bottle.
  • SteriPEN: inactivates bacteria, viruses and protozoa in clear water but removes nothing.
  • LARQ PureVis 2: useful for selected bacteria, bottle self-cleaning and specified tap-water contaminants, but it does not publish the same broad all-three-pathogen evidence.

For clear but uncertain water in India, South Sudan or Haiti, the practical order is:

  1. GRAYL GeoPress for the broadest all-round protection;
  2. Water-to-Go 75cl Eco Active when low bottle weight and no battery matter more than pourable treated water;
  3. SteriPEN Ultra or UltraLight when low weight matters, the water is clear and charging is reliable;
  4. LARQ PureVis 2 for already treated urban water rather than genuinely uncertain sources.

No bottle can protect against illness from contaminated food, ice, hands, utensils or surfaces. No ordinary travel bottle should be relied on for seawater, fuel, mining runoff, industrial pollution or severe chemical contamination.

Evidence for the guide

Sources for this pathogen guide

General travel-health information, not personal medical advice. Manufacturer percentages and efficacy statements are identified as product claims; country judgements are scoped to the available evidence.