SteriPEN Ultra Water Purifier Review

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Over the past eight months the SteriPEN Ultra has become my go-to backpacking water purifier. Previous SteriPEN models had design and functionality flaws that severely impacted their performance, but my experience with the Ultra has been a different story. The Ultra is easy to use, works fast, kills all the bad stuff (protozoa, bacteria, and viruses), and best of all, it doesn’t require any pumping, squeezing, backflushing, or chemicals. Like all backcountry gear, there are downsides to the SteriPEN Ultra, but on the whole, I think it’s an excellent choice for backcountry water purification.

Quick Specs

Katadyn Steripen Ultra

Best UV light water purifier

Price: $130

Weight: 5 oz.


  • Lightweight
  • Compact
  • Quick & easy to use
  • Kills viruses


  • Expensive
  • Batteries can fail
  • Won’t work in murky water


Ease of use is one of the Ultra’s key strength and the main reason it’s won me over. With a standard small-mouth 1L water bottle, the SteriPEN is just about the most convenient and hassle-free water purifier I’ve ever used. Directions:

  1. Press power button once to purify 1 liter or twice for the 1/2L setting.
  2. Place Ultra in a small-mouth water bottle, flip upside down, and gently rotate to move the water around. The rubber seal won’t allow water to leak out.
  3. A countdown will start on the display screen once the Ultra is in water. It takes 90 seconds to purify 1L or 48 seconds to purify half a liter.
  4. When time is up, the Ultra will show a smiley face indicating your water is ready to drink.

Steripen Ultra Specs


Cost is one of the biggest downsides to the SteriPEN Ultra. Though much cheaper than the best pump filter (MSR Guardian), the Ultra is more than twice as expensive as the popular Sawyer Squeeze. That said, I personally feel the convenience of the Ultra makes it well worth the price, especially if you plan to put it to good use over many years.


5 ounces (4.7oz on my scale). The Ultra is light enough to take on any backcountry trip, including thru-hikes. It isn’t quite as light as the Sawyer Squeeze (3oz), but the minimal weight difference is well worth the upgrade in convenience. In addition, the Ultra weighs less than half as much as popular pump filters like the Katadyn Hiker Pro (11oz) and MSR Guardian (17oz). Water purification chemicals like Aquamira (2oz) tend to be the lightest option, but you’ll have to wait 30 minutes before drinking and I prefer chemical-free water whenever possible.

Purification Method

The Ultra uses ultraviolet (UV-C) light rays to safely purify clear water. The UV rays destroy 99.99% of protozoa (including Giardia and Cryptosporidia), bacteria and even viruses. The downside with UV purification is that it won’t work with murky, sediment-laden water. Most pump/squeeze filters quickly clog in those conditions as well, so this isn’t a complete tradeoff. The majority of my backpacking trips are in climates where, especially with a little planning, I know the water sources will be clear enough for the Ultra. If I am forced to drink from an unideal source, I can always strain out particles or use a chemical tablet for certainty. If you commonly expect to purify water from murky sources (mud puddles, animal pastures, etc.) and you want to avoid chemical treatments, you may be looking for a beast like the MSR Guardian.


Internal Lithium-ion battery. The Ultra comes with a built-in rechargeable battery and USB cord for charging. This means you won’t have to worry about replacing expensive, heavy, and hard to find batteries like previous models.

Battery Life

The Ultra will purify 50 liters on a full charge, which works out to roughly a 10 day water supply for one person or 5 day supply for two (4-6L per day depending on conditions). That daily estimate is based on my personal experience and is actually a little conservative (I’ve purified well over 50L on a single charge). I initially didn’t like the feeling of having my water treatment method tied to a battery, but over time the Ultra has gained my trust.

Lamp Life

The bulb in the Ultra is rated to work up to 8,000 treatments before it burns out. At 4-6L per day, that’s the equivalent of 4.4 years of clean water for one person. Also, if you do actually use up your Ultra bulb, SteriPEN will replace your Ultra for free.


7.3 x 1.65 x 1.3 inches. The SteriPEN Ultra is about 1 inch longer than a standard pen and about as wide as a golf ball at its thickest part. It easily stashes away in a side pocket or front mesh pouch for quick access.


The Ultra has a straightforward display that works well. Simple symbols display the unit’s battery life, lamp life, liter settings, a countdown timer, a smiley face when the water’s ready to drink, or a frowny face if something goes wrong. The display will be upside down while purifying with the plastic bottle method, but it’s still easy to read.

Backup Purification

I’ve started using my phone for photography on most backcountry trips, so I’ve also been bringing a small Mophie power bank to keep it charged. If need be, I could use my power bank to recharge the Ultra, but so far that hasn’t been necessary. Also, I always bring backup purification pills just in case I have an equipment malfunction or encounter a truly gross/murky water source.

Water Bottles

I use my SteriPEN Ultra with cheap 1L plastic water bottles that have standard small-mouth openings. There’s nothing special about the bottles themselves, they’re just light, strong, affordable, and easy to replace. Smartwater bottles tend to work well because they’re long and skinny, which makes them easy to fit into backpack water bottle holsters.


The Ultra feels very sturdy and I expect it to last for a long time, even in tough conditions. There’s a hard case that covers the bulb of the Ultra and a soft case that protects the entire unit. The bulb of the Ultra is glass, so be careful not to drop it when the bulb is exposed. With a little care, I expect the ultra to last for many years of tough backcountry use.

Bottom Line

The main reason I like the SteriPEN Ultra is its convenience compared to other purifying methods. With the Ultra, I no longer have to awkwardly crouch over streams and tire out my forearms pumping water. I also avoid squeezing cold bags/bottles to filter my water, which tires my hands and chills my fingers. Instead, I have a hassle-free purifier that that provides clean, safe drinking water in 90 seconds with minimal effort. While the Ultra isn’t the lightest or cheapest purifier and on the market, its considerable strengths make it my go-to choice for water purification.