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Reviews > Water Treatment > Ultraviolet > Meridian Design mUV Treatment Device > Test Report by Rick Allnutt

Meridian Design mUV Water Purifier Meridian Design mUV Water Purifier
Test Series by Rick Allnutt

Initial Report - May 24, 2007

Field Report - July 26, 2007

Long Term Report - October 2, 2007


NAME: Rick Allnutt
AGE: 54
LOCATION: Helotes, Texas
GENDER: male
HEIGHT: 6' 0" (1.80 m)
WEIGHT: 183 lb (83.00 kg)

Over the last several years, I have become an ultralight camper with a three-season base pack weight of about 8 lb (3.5 kg) and skin out weight of 17 lb (8 kg). I have completed many section hikes on the Appalachian Trail (AT) in all four seasons, and many trips to state parks, with a total mileage of about 1360 miles (2200 km). I am a gearhead, a hammock or tarp camper, and I make much of my own equipment. 

Trail Name: Risk

Risk's Ultralite Hiking Page:

May 24, 2007


Manufacturer: Meridian Design
Year of Manufacture: 2007
Manufacturer's Website:
MSRP: Not Listed
Listed Weight: 2.4 oz (68 g)
Measured Weight: 2.4 oz (68 g)
Measured Weight of Water Filter Screen 0.1 oz (3 g)

mUV being used in Big Bend Nat Park INITIAL IMPRESSIONS

The mUV device is surprisingly light and small. Its clear plastic shell allows me to see many of the workings of the device, including wiring, electronic chips, and the plastic resin used to seal the unit's quartz light bulb in place.  It is not yet listed on the Meridian Design website, but a pre-release PDF file had prepared me for the appearance and function of the purifier. The device was precisely what I expected from the release.

The mUV has only one control, a push button under a silicone bubble next to the central metal plug on the top surface of the device. By pressing the button once for 2 seconds, the water purification cycle begins. By pressing it briefly two times, the LED light comes on for several minutes. 

The central metal plug fits into the plastic case with a twisting motion and is very secure. But there is no O-ring or other provision to keep water from entering the device through that hole. Because of that lack of water-proof seal I will be unable to carry the device in an outside pocket exposed to the rain. I will also need to be very careful not to allow water to wet the top surface and drip into the electronic portion of the purifier.

The device has a plastic cover designed to protect the quartz bulb from impact in my pack. This cover glows in the dark to make it a little easier to find, though it is also tied to a bail on the central metal plug.  Only when the plug is removed for charging is the cover not attached to the device.

Inside the head of the purifier, and readable through the clear plastic, is a small sheet which explains the operation of the device. This sheet reminds me that to purify water, the push button is held in for two seconds. The internal instructions also notes that pressing the button twice will turn on the white LED for a short period of time.  
The provision for charging the internal lithium battery is very clever. By removing the central metal plug, two leads are exposed with magnetic end plates. These can easily be attached to a battery for charging. The instruction sheet that comes with the mUV says that the red wire is attached to the positive side of the battery and the black wire is attached to the negative side of the battery.

It would help me, especially when tired, if there were some reminder on the device or the wires as to which lead is expected to be attached to the positive and which is negative. When the leads are hooked up correctly, a white LED light inside the device blips for part of a second every few seconds. The instructions say that if the battery is not hooked up correctly, the LED does not blip. How well the device is protected from being hooked up backwards is not clear from the instructions, though there is not dire warning about any problem from doing so.


A four page instruction sheet is contained with the device. It explains that UV light is irritating and should not be directly observed without the tip being in water. The directions note that the tip should never be placed in the mouth or any other body opening, as this could cause a UV burn of the tissue near the quartz light.

The instruction sheet explains that if the battery cycles very deeply, that charging with a 9 volt battery may be necessary to reset the device. Missing from the instruction sheet are the directions for turning on the LED light for use as a lantern.  
(Press the button twice, as explained on the small sheet internal to the head of the mUV.)


I charged the mUV for about 3 hours with a single D cell battery, ensuring that the red wire was attached to the positive terminal of the battery, and the black wire was attached to the negative side of the battery. The white LED blipped every few seconds during this time. After initial charging, I stowed the leads in their metal cap and pressed the top button for two seconds. The white LED flashed for 3 or 4 seconds and the quartz light flashed on. After just a moment, the white light of the quartz light went off and the heater filament of the quartz bulb remained on for about twenty minutes, gradually diminishing in brightness.

I called and left a message for the Meridian Design engineer and he called me back within the hour. He confirmed that this was abnormal behavior for the unit. I have returned the device for testing and replacement as necessary as the company has requested. I asked about the protection circuit for reverse polarity charging. He said that the unit could be hooked up backwards to a 1.5 volt battery for a few seconds without harm, but that leaving it attached would not be good for the chips on the circuit board.


I really like the light weight of the device. From reading about UV water purification, I am excited to try this on several water sources that I would not normally consider for water supply while outdoors. I have concerns about using a device meant to be immersed most of the way in water which can inadvertently let water in through the top plug. I also have concerns about the battery wires, that I may forget one late night that red is positive and black is negative. It has happened to me before.

July 26, 2007

Water source in Lost Maples SP Texas FIELD LOCATIONS AND CONDITIONS

I have used the mUV device on almost every hike I have taken over the last two months. I have used it on stream water in Government Canyon, near San Antonio, Texas a number of times. This water comes out of an underground aquifer but also may have run off from ranching land nearby. I have used the water from the Texas canyon at Lost Maples State Natural Area, seen to the right, where the water comes from a mixture of ranch and park lands. The mUV is also the only device I have used to purify water in Big Bend National Park. This water in the Basin is clear, but only about a mile downstream from the sewage treatment plant at the lodge in the park. The altitudes I have carried and used the device range from about 600 ft (180 m) to a little over 8000 ft (2400 m). The temperatures have been uniformly warm, with air and water temperature probably never below 60 F (16 C). 


Within a week of my posting my Initial Report, my new/replaced mUV arrived and it performed exactly the way the instructions said it should. It goes through its purification cycle every time, and by timing the pressing of the button to two short clicks, it can be used as a hand-held LED light.  (The directions do not document it, but the light can be turned off by pressing the button one more time - it is not necessary to wait out the 12 minute time out cycle.)

I have used the mUV on several bottles.  I tried using it with a 22 oz (650 ml) used plastic soft drink bottle. With this bottle, the business end of the device fits snugly in the opening.  It works best to have an air bubble the size of a marble or two in the bottle and to turn the bottle alternately upside down and then right side up, letting the bubble mix the water.  This same technique can be used in a two qt (2 L) bottle. 

I have also used the mUV in 1 qt (1 L) sports drink plastic bottles.  In these bottles, the opening is larger and my technique has been to fill the bottle most of the way to the top and then to use the bulb of the device as a stirring rod. A picture of me doing this has been inserted in the Initial Report above. 

I tried to use the device in a 3 qt (3 L) plastic soft drink bottle, but the larger bottle is very hard to use in purifying water. The opening of this bottle is too big to be plugged by the device. Its volume is too big to effectively stir with the end of the mUV. I ended up using the larger bottle as a reserve and filling the smaller bottles and then purifying the water in the smaller bottles. 

Ease of use: This is where the mUV "shines".  Pun intended. Get water in bottle. Pull the cap off the mUV. Press button for 2 seconds, until the LED begins to flash. Put bulb in the water. Stir. In 90 seconds, the water is safe to drink. Period (full stop). It makes a hot Texas day feel good when a pool of clear water is at hand - see photo to right.

I have not used the mUV to exhaustion.  On three day trips, I have not needed anything like the advertised 20 liters of water on a single charge. Before a trip like this, I have charged the device before leaving - just like I do my camera battery. I find no use for a rechargeable device which is discharged at the wrong time on a trip. When I have charged the device, the LED has blipped on for many hours.  At the end of 8 hours I gave up waiting for it to stop, figuring that it was surely charged enough. I have also used the mUV without further charging over several weeks of use.  It holds a charge quite well.  

Because the mUV does not have a waterproof top, I store it in my pack with other items which I want to stay dry.  I have a "waterproof safe" consisting of a Seattle Sport bucket which I roll up in the pack for this purpose. Nothing in it has ever gotten wet in the hardest rain. I have had no problem with the mUV getting wet while I am stirring with it or turning it upside-downside-up in the mixing period. 


The mUV is doing everything I want it to do. It has kept me healthy when I have used water from streams, though I know that they feed from ranch lands. The folks that I have shown this little gem to - filter carriers all - love the idea of it. They want one as soon as it makes the market. Check back here in late September for the results of my long term testing of the mUV.

October 2, 2007


I have continued to use the mUV device for water on numerous day hikes and back-country mountain bike rides in state parks in Texas.  I spent two nights at Hill Country State Natural Area at the Wilderness campground.  Temperatures have been very warm, with highs of about 95 F (35 C) and lows about 70 F (21 C). The altitudes I have carried and used the device ranged from about 600 ft (180 m) to a little over 1000 ft (300 m). Water temperature probably never was below 60 F (16 C). 


The mUV has continued to operate flawlessly.  Its internal battery is very robust, and I have come back to the purifier weeks after a charge and found that it still had plenty of juice to treat another liter of water. I was never able to completely run down the battery, but I did not try to do so. If I was going out on a trip and it had been several weeks since I had used the mUV, I usually charged it. None of my trips were of a length that required charging the battery during the trip, though I was prepared to do so. 

During the test period, I have continued to read about ranch water sources and now believe, more than ever, that using water treatment here in Texas is an important preventive health measure for my hiking. The sources I was able to find convinced me that the treatment method was effective and safe. 

Using the mUV is certainly the simplest and fastest water treatment I have experienced. It is a great advantage to me, to be able to enjoy the fresh taste of outdoor water without the odor of chlorine or iodine. It goes without saying that I have not been ill at any time during the testing phase - no upset stomach, and nothing worse. 


The mUV has earned a permanent place in my overnight and day hiking gear.  Whenever I gather water, I will use this lightweight and problem free purifier.

Read more gear reviews by Rick Allnutt

Reviews > Water Treatment > Ultraviolet > Meridian Design mUV Treatment Device > Test Report by Rick Allnutt

Product tested and reviewed in each Formal Test Report has been provided free of charge by the manufacturer to Upon completion of the Test Series the writer is permitted to keep the product. Owner Reviews are based on product owned by the reviewer personally unless otherwise noted.

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