And that's the main reason why portable water filters (purifiers) have become an important necessity for travelers, hikers, campers, backpackers, as well as for emergency water needs. 
However, not all portable water filters are created equal.
Each will come with different features that provide different results.
So to get the right unit that fits perfectly to your need, the guide below will help.
Choosing Your Best Portable Water Filter
1. Filter Types
• Ceramic - has a long life (mostly can last up to 2,000 liters) and can be cleaned many times before being replaced. Unfortunately, it can get clogged easily.
Some of the ceramic filters can also come with a carbon core, which helps to remove chemicals from water.
• Structured Matrix - dense and honeycombed material that can strain out really tiny pathogens.
• Fiberglass - more fragile than ceramic, but still effective at eliminating particles.
• Hollow Fiber - allows water through tiny pores and into the core, where pathogens are strained out.
• Silica Depth - works by having multiple levels of different sized grains, going from largest to finest.
It catches different sized particles and organisms as water is pushed through its levels of density.
2. Micron Size
A measurement of the pore size in the filter media. The smaller the pore size, the more pathogens the filter can strain out. 
3. Flow Rate
Flow rate shows how fast a unit processing the water.
A flow rate of greater than 1 liter per minute is fast enough. The rule of thumb is, the larger the surface area of the filtering medium, the faster the flow rate.
4. Other Features To Consider:
• EPA Certification
5. What Other Users Have Said
There is a great advantage if you buy your portable water purifier online is that you can see directly the opinions of other users.
And that is why large and trusted online retailer like Amazon.com displaying their customer reviews including the star rating. It will give you a real picture of a product you plan to buy.
The more the number of buyer reviews and the higher the star rating, the better the product in the eyes of consumers.
For your information, people who can submit a product review on Amazon.com must make the purchase first. So rest assured, you will get an honest review from them.
Now, get yours!!!
Top 10 Best Portable Water Filters
1. LifeStraw LSPHF017 (under $20)
• Reviewed by 4.889 verified buyers - 4.7 out of 5 stars - READ REVIEWS
• Award-winning LifeStraw has been used by millions around the globe since 2005
• Removes minimum 99.9999% of waterborne bacteria (>LOG 6 reduction)
• Surpasses EPA standards for water filters
• Removes minimum 99.9% of waterborne protozoan parasites (>LOG 3 reduction)
• Filters to an amazing 0.2 microns
• Filters up to 1000 liters of contaminated water WITHOUT iodine, chlorine, or other chemicals
• Comes in a sealed bag, perfect for storing for emergencies
• Dimensions: 8.9 x 1 x 8.9 inches ; 1.8 ounces
2. Sawyer Products (under $20)
• Reviewed by 3.089 verified buyers - 4.7 out of 5 stars - READ REVIEWS
• Ideal for outdoor recreation, hiking, camping, scouting, domestic and international travel and emergency preparedness
• High performance filter fits in the palm of your hand; weighs just 2 ounces; 0.1 Micron absolute hollow fiber membrane inline filter
• Attaches to included drinking pouch, standard disposable water bottles, hydration packs, or use the straw to drink directly from your water source
• Removes 99.99999% of all bacteria, such as salmonella, cholera, and E.coli; removes 99.9999% of all protozoa, such as giardia and cryptosporidium
• Filter rated up to 100,000 gallons; includes 16-ounce reusabel squeeze pouch, 7-inch drinking straw, and cleaning plunger
• Dimensions: 8 x 3.5 x 3 inches ; 4.8 ounces
3. Brita Filter Bottles (under $20)
• Reviewed by 1.205 verified buyers - 4.0 out of 5 stars - READ REVIEWS
• 20 ounce soft sided water bottle with 1 filter
• 1 water filter can replace 300 standard 16.9 ounce water bottles
• Filter sits inside water bottle, reducing chlorine taste and odor, often found in tap water
• BPA free reusable water bottle features drink spout and is top rack dishwasher safe
• Replace filter every 2 months with black Brita Bottle Replacement Filters
• Dimensions: 2.9 x 2.7 x 9.5 inches, 4 ounces
4. LifeStraw Go Water Bottle (under $29)
• Reviewed by 933 verified buyers - 4.3 out of 5 stars - READ REVIEWS
• 23-ounce water bottle with integrated replaceable LifeStraw filters up to 264 gallons (1,000 liters) of water down to 0.2 Microns
• Leak-proof bottle made of BPA-free Tritan can be re-used indefinitely
• Surpasses EPA standards for removing E. Coli, Giardia and Cryptosporidium oocysts, and many other waterborne contaminants
• Removes 99.9999% of Waterborne bacteria (> log 6 reduction), removes 99.9% of Waterborne protozoan Parasites (>log 3 reduction)
• Zero aftertaste, no chemicals or iodine, food-grade flexible silicone mouthpiece is removable for easy cleaning
• Dimensions: 3 x 3 x 9 inches ; 3.8 ounces
5. Sawyer Products PointOne (under $50)
• Reviewed by 744 verified buyers - 4.7 out of 5 stars - READ REVIEWS
• Complete water filtration system designed for emergency preparedness, groups in the backcountry, and mission trips
• Highest level of filtration on market -- removes greater than 99.99999% of all bacteria and 99.9999% of all protozoa
• Bucket and faucet adapters provide high-volume clean, potable water from any fresh water source; easily field maintainable
• Filter with built-in and removable push/pull cap; comes with one 32-ounce, BPA-free collapsible pouch for personal hydration
• Backed by manufacturer's lifetime limited warranty (Independent Testing Laboratory Hydreion, LLC.; Microbiological Report S05-03)
• Dimensions: 3.5 x 6.1 x 6.1 inches ; 10.1 ounces
6. Survivor Filter PRO (under $60)
• Reviewed by 580 verified buyers - 4.3 out of 5 stars - READ REVIEWS
• Independently Tested at Intertek Labs in Columbus Ohio to show Removal of - 99.9% Virus, Staph and Bacteria - and Reduces Heavy Metals - 99.5% of Mercury and 93% Lead - surpassing EPA standards for water filters
• Produces a super-fast flow rate of 500 ml, (17 ounces) per minute, Fully Compact at 6.5 inches long. Comes Assembled with Detailed Instruction Manual, Tubing, Carry Bag, Attachable Cup, Membrane, Carbon and 2 Cotton Filters
• 3 Ways to Use - directly from fresh water source, pumped into Attached Cup and pumped into any portable hydration device/pack. Perfect for filtering large jugs of water for the whole family!
• Triple Absolute Filtration to 0.01 Microns with Cleanable Ultra Filter and replaceable Carbon and Cotton Pre-Filter. Outer Shell Made of Military Grade BPA Free ABS Material
• Include: Free Carry Bag, Attachable Water Cup + 2 Cotton Pre-Filters
• Survivor Filter Full Money Back Guarantee and Lifetime Warranty
• Dimensions: 3.5 x 6.1 x 6.1 inches ; 10.1 ounces
7. Survivor Filter (under $30)
• Reviewed by 568 verified buyers - 4.7 out of 5 stars - READ REVIEWS
• Best Independently Tested Filtration Level on the Market Today with Virus, Bacteria and Heavy Metal Filtration Independently Tested in the USA: Tested at Intertek Labs in Columbus Ohio to show Removal of 99.9% Virus, Staph and Bacteria and Removes Heavy Metals surpassing EPA standards for water filters.
• Reusable with Cleanable and Replaceable Internal Filter Cartridges: Unlike other brands you Never Need to throw it out. 3 Stages of Water Filtration to 0.05 Microns with a Cleanable Ultra Membrane Filter up to 100,000 Liters (26,417 Gallons), Replaceable Carbon Filter up to 1000 Liters (264 Gallons) and a Cotton Pre-Filter with 5 Extras Included
• Built to Last Forever with a Lifetime Warranty: It's Made of Military Grade BPA Free ABS Material, has a Special Flip Top and Mouthpiece and Produces a super-fast flow rate of 200 ml. (7 ounces) per minute, Double with our Canteens! It also comes with Detailed Instruction Manual.
• Dimensions: 1.4 x 1.4 x 7.1 inches ; 3.5 ounces
8. Etekcity (under $19)
• Reviewed by 479 verified buyers - 4.7 out of 5 stars - READ REVIEWS
• SAFETY TESTED: This water purifier has been tested by the TÜV SÜD Institute and meets EPA Water Quality Standards. The pouch complies with the FDA's Food Contact test in accordance with 21 CFR 180.22 to ensure maximum quality and safety
• HOLLOW FIBER UF MEMBRANE: Antibacterial carbon filter cleans to 0.01 Microns, eliminating 99.9999% of colibacillus, legionella, heavy metal ions, chlorine, volatile organic compounds (VOC), organic and insect contaminant
• FILTER MORE: This filter will provide up to 1500 liters or almost 400 gallons of safe drinking water
• HYDRATION RESERVOIR COMPATIBLE: Attach the Etekcity Personal Water Purifier to most hydration reservoirs for increased water carrying capacity and convenience
• INCLUDED ACCESSORIES: A foldable water pouch, extension tube, pre-filter, and backwash device are all included at no extra cost. Carry water with you, reach further to get water without strain or danger, get extra filtration, and keep the filter clean and clog-free
• 2-year warranty
• Dimensions: 1.9 x 5.1 x 7 inches; 2.1 ounces
9. LifeStraw Family (under $58)
• Reviewed by 464 verified buyers - 4.6 out of 5 stars - READ REVIEWS
• Award-winning life straw family is used by over 13,200,000 people worldwide
• Clean drinking water for a family of four for 3 years
• Gravity filter - pour water in the top and clean water comes out the bottom
• Flow rate of 9 -12 liters per hour
• Purifies 18,000 liters/4755 gallons without iodine, chlorine, or other chemicals
• Award-winning LifeStraw Family is used by over 13,200,000 people worldwide
• Surpasses EPA standards for water purifiers: removes 99.99% viruses, 99.9999% bacteria and 99.9% protozoan cysts to 0.02 microns
• Purifies 18,000 liters/4755 gallons WITHOUT iodine, chlorine, or other chemicals; Clean drinking water for a family of four for 3 years
• Gravity filter - pour water in the top and clean water comes out the bottom; Comes in a sealed bag, perfect for storing for emergencies
• Dimensions: 11 x 9 x 4.5 inches ; 1.5 pounds
10. Katadyn Vario (under $85)
• Reviewed by 418 verified buyers - 4.5 out of 5 stars - READ REVIEWS
• Dual pumping modes
• Removes particles
• Activated Carbon reduces chemicals
• Suitable for backpacking
• Glass fiber filter
• A simple turn engages a ceramic pre-filter for long life in dirty water or a pleated glass fiber filter in normal conditions
• Produces up to two quarts per minute in the faster flow mode and one quart per minute in longer life mode
• Replaceable carbon core keeps water tasting fresh; reduces chemicals, odors, and toxins throughout the life of the cartridge
• Dual piston technology provides maximum output with minimum effort
• Adapter base attaches directly to water bottles or an output hose can be used to fill hydration systems or larger containers
• Dimensions: 10 x 10 x 4 inches ; 1.8 pounds