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Reviews > Water Treatment > Filters > Guyot Designs TapGuard > Test Report by Kara Stanley

September 08, 2009



NAME: Kara Stanley
EMAIL: karguo (at) yahoo (dot) com
AGE: 26
LOCATION: Tampa, Florida
HEIGHT: 5' 10" (1.78 m)
WEIGHT: 175 lb (79.40 kg)

I backpacked for the first time in 2006 and am now hooked. I have hiked most of my life in the South on flat land or small hills. When living in the DC area I got into hiking, doing both day hikes and multi-day backpacking trips, but warm weather hikes only! I am working on converting to a lighter hiking style as money permits. My base-pack weight is around 23 lb (10 kg) since I am still carrying a heavy backpack. Now living in Florida most of my hikes are day or short overnight trips on flat/swampy land.



Manufacturer: GuyotDesigns
Year of Manufacture: 2008
Manufacturer's Website:
MSRP: filter and 2 cartridges US$15.95; replacement 2 cartridge pack US$5.95
Listed Weight: not listed
Measured Weight: 1.5 oz (43 g)
Color options: Tahoe Blue, Tangerine, and Black


Bottom view of filter without cartridge
The packaging was small so that there is not an excess of packaging material, which was an added bonus since the filter's purpose is to reduce plastic water bottles going into landfills. It was very easy to open the package and take out the filter and the 2 cartridge packs. Each cartridge is packaged separately with a sticker on it stating "rinse under running water for one minute before using." The filter itself is squishy, fun to play with and didn't have a chemical or "new product" smell.


The instructions were easy to follow and each filter package has instructions to rinse under running water for one minute before using. Then you just open the bottom on the filter and insert the cartridge and close the tap. Once all that has been done you align it flush with the top of a wide mouth bottle. It would have been helpful if the instructions mentioned that you actually need to suck on the filter like its a straw in order to drink out of it. At first I kept tipping the bottle to high and spilling water all over myself but have figured out how to drink out of the filter without spilling.


After opening the package and looking everything over, I rinsed the filter under running water for one minute, which I didn't time, but will with the next filter. Its easy to pop the cartridge into the bottom on the filter. Once the filter was assembled, I placed it in my wide-mouth bottle (I'm using a Cyclone bottle by Outdoor Produces). It did take me a few tries to get the filter lined up flush with the top because the filter is squishy easy to push in too far. Once the filter was in place, I filled it up with tap water and starting drinking and spilling. In order for water to flow through the filter you have to suck on it much like a sports bottle top or straw, but until I figured that out, I tip the bottle too high and spilled water all over. I did have some issues with carbon dust ending up in my bottle and will take extra care and time when rinsing my next filter cartridge.

I did knock the bottle off the table one time and this caused the bottom to open and the filter cartridge to fall out into the bottle. This would be an issue for me while backpacking as I try to minimize touching my food and water while on the trail to prevent illness. I'll be dropping the bottle in future to see if this result is repeatable or it I just didn't have the bottom closed tight enough.

So far I haven't tasted a difference between the filtered and unfiltered tap water, but the tap water in my area does not have a noticeable amount of chemicals or a strong chlorine taste or smell. I am interested to see how this does while out backpacking and chemically treated my water since I do not use a produce to remove the chemical taste from my water.


I Like:

Good for the environment

Easy to use

Filter doesn't have a taste

Can drink virtually all the water out in the bottle through the filter

I Don't Like:

Filter cartridge fell out when dropped

Had carbon dust in first few bottles of water

No sanitary way to share filtered watered or have extra filtered water on the trail for cooking since it must be sucked through the straw-like filter.



I have been using the filter for my day-to-day life, taking it to school and work with me. Most of the water that I've drank through the filter was been at room temperature (about 70F or 21C), though I have drank some hot water through it after leaving the bottle in the car on a sunny day or cold water after filling up the bottle from a water fountain. I also took in on a camping trip, but cartridge rupture prevented me from testing it out. All the testing has taken place in great Tampa Bay area with an average late spring/early summer day time temperature of 85-95 F (29-35C).


I carried this bottle around with me to work and school most days. While I enjoyed known that my water was filtered, I could not tell a difference between the filtered and unfiltered water. This is probably due to low chemical levels in the municipal water supply.
Bottle full of charcoal filter grit

The broken filter cartridge in the bottom of the bottle

I also took the bottle on a car camping trip to Long Key, Florida. I had planned to test it out with a difference water supply and on some short hikes. During the course of the trip the cartridge fell out of the bottle, I then left it in the back seat until I got to a gas station, probably about 2 hours after the cartridge had fallen out of the filter. At that point the filter cartridge had ruptured and the bottle was full of charcoal. I was unable to continue the test at that time since did not take the second filter cartridge with me.

For the second cartridge I made use that I washed the filter for at least 2 minutes since with the first cartridge I still had charcoal particles in my bottle for several days after washing it for only a minute. This extra wash time did reduce the amount of charcoal in my bottle, was it was still noticeable and I still got a few mouthfuls of water with charcoal grit, not tasty!

I also did an experiment with the filter to see if it had any noticeable effect on water that had been purified using purification tablets (mine were imported from Germany and are made up of sodium dichloroisocyanurate (NaDCC) 4.5 mg & silberchlorid (Ag+) 0.1 mg per tablet to treat one liter of water). After purifying a bottle of water, I then drank unfiltered and some filtered. I did notice that slight difference between the filtered and unfiltered waters, with the filtered tasting better. This was not a major taste difference for me so probably wouldn't take it backpacking with me.


Overall I did not find this filter to be something that I will continue to use since I did not notice a difference between filtered and unfiltered water. The issue with the cartridge fall out if the bottle is dropped or bumped against something is annoying and since my hands are not sanitary all the time I often have to wait until I have a chance to wash them before I replace the filter. This would not work well while backpacking since I try and avoid touching my food and water as much as possible due to sanitary issues. Plus, I would not want to carry along an extra filter or two just in case the one I was using ruptured.

If you are looking for a potable water filter to use in the front country, this one is okay. During testing, the filter never made the water taste funny or like plastic nor did is smell like chemicals, even when left in a hot car all afternoon. This could be a cheap and eco-friendly way to replace bottled water.

Bottom line: Okay for front country use, no place for it in the back country.



I had plans to make this filter with me on a three-week trip to Central America, but due to the second cartridge breaking apart when it was removed to clean out the filter and bottle, I was unable to take it with me. So all my testing has been done in the greater Tampa Bay area in the same conditions listed above


Overall this filter-cartridge package did not perform well. First the cartridge broke on the way to a camping trip, leaving me with a mouth full of grit and the second cartridge broke just a few days before trip not allowing me time to purchase replacements before leaving. The second cartridge ruptured with fewer than 10 L of filtering under its belt. I had taken the filter out clear the bottle and removed the cartridge to wash the filter and also rinse the cartridge pack again since I was still have a little bit of residual grit in my water bottle. While rinsing out the cartridge, it simply came apart at the seams in my hand and I was left holding grit.


With such weak performance under daily use in the front country, I see no reason to take it with me into the backcountry. I also never noticed a taste difference between filtered and unfiltered water even though I drank for a variety of local sources (water fountains in various buildings, my home tap, and chemically purified water). Also with both filters breaking before they needed to be replaced, the cost of using this system is increased (2 cartridges for US$5.95 / 2 = US$2.97/10 L= US$0.297 per L for the second cartridge, which is pretty price for water in my book).

I do love the idea of this filter because I try to reduce my waste and like to take eat and drink health, but it needs more work so that the cartridges last their full 200 L lifespan.


I will not be using this filter system in the future for various reasons:

* Cartridges do not last
* Cartridges must be ordered unless you are close to a REI store which adds to their final cost
* No noticeable change in water taste

A big thank you to the Guyot Designs people as well as all those at the for allowing me to be a part of this test series.

This report was created with the Report Writer Version 1. Copyright 2009. All rights reserved.

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