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Reviews > Water Treatment > Solar > Test Report by Kerri Larkin




Image from website


Kerri Larkin
kerrilarkin at yahoo dot com
Coffs Harbour, New South Wales, Australia
5' 9" (1.75 m)
240 lb (109 kg)
I've been a car-camper and bushwalker for thirty years. Mostly I do day hikes as my passion is photography, which means I walk very slowly! I've returned to walking after some years away due to injuries and I'm learning to use Ultralight gear (and my hammock!). I've traveled most of eastern Australia, walking in landscapes as diverse as tropical rainforest, snow fields, beaches and deserts. My fortieth birthday was spent trekking in Nepal which was a truly life changing experience.



Year of Manufacture:
Distributor's Website:
$US 99.99

SolarBag Measurements
Capacity: 0.92 gal (3.5 l)
Weight Listed:
Measured Weight
4 oz (105 g)
4 oz (109 g)
Listed Height:
Measured Length:
15.7 in (40 cm)
15.6 in (39.5 cm)
Listed Width:
Measured Width
9.65 in (24.5 cm)
10 in (25 cm)
BPA-free "engineered bi-layer plastic" bag. The outer layer is designed for toughness and the inner layer is BPA-free for contact with water. Recyclable.
Nanotechnology inner mesh purifier. Can be sent to landfill after useful life
Not stated


I've been so looking forward to this test! The SolarBag appears to be a completely revolutionary way to filter water based on nanotechnology rather than current methods. Water is becoming the single most precious resource on the planet and many countries don't have access to clean, safe, reliable water. It's something often taken for granted in the the First World countries. And yet... Even rural areas in 'civilized' countries are also finding increasing issues with Giardia, pesticides, heavy metals and viral contamination. It's becoming harder and harder to get a good drink! When I first started bushwalking, I would never think twice about drinking out of virtually any mountain stream I came across, but now, I have a lot less confidence in our 'clean' water.

While most current technology for filtering water relies on mechanical filtration, UV exposure or heat (good ol' fashioned boiling of water), each has drawbacks. UV sterilisers need batteries, mechanical filtration can require a lot of pumping and boiling requires a source of heat. That's where the SolarBag is different: all it needs is sunlight. In fact, in as little as 2-3 hours of direct sunlight the makers claim it's possible to completely purify 3.5 liters (0.92 gallons) of water. With the right weather, up to 10.5 litres (2.7 gallons) in a single day.

This is gonna be interesting!

My SolarBag arrived in a lovely cardboard presentation box with a wealth of information on it. Perhaps the most interesting is the back panel which shows in table-form exactly what the SolarBag is claimed to remove from water: Bacteria, viruses, protazoa, pesticides and herbicides, petrochemicals (gasoline and oil), pharmaceuticals, arsenic, lead and mercury. The table also suggests that filters, chemical tablets, UV sterilisers and boiling will only remove bacteria, viruses (not filters) and protazoa.

There were also some simple instructions on how to use the purifier and a bit of information on how the nanotechnology mesh works.

collage 1
Packaging detail

Inside the box was my SolarBag and a simple instruction sheet. Interestingly, the SolarBag was loosely folded in half despite having clear instructions printed on it saying "Do Not Fold". My guess is that repeated folding would damage either the seams of the bag or the nanotechnology inner mesh.

The first thing that struck me was just how big the bag is, but then, it does have a 3.5 litre (0.92 gal) capacity listed on the box, the website and in the instructions but "3-liter capacity" is printed on the bag. It will be interesting to see which is correct when I fill the bag.  The front of the SolarBag is printed with some simple pictographs showing how to use the bag, the main contaminants it removes and that the bag has a dry shelf life of seven years.

At the top of the bag is a lovely wide-mouthed filler cap which will make it easy to fill the bag from almost any water source. The blue plastic cap is tethered to the bag to prevent loss, which is an excellent idea. Tethered to the tether is a small bag which looks like a coffee filter. This is the pre-filter which is designed to remove most of the larger contaminants when the bag is being filled. Initially, I thought it was a good idea to have this pre-filter tethered to the SolarBag so it doesn't get lost but on thinking about it, I'm not so sure it is. It seems like it will be very easy for the pre-filter to become quite grubby if dangling around on the outside of the bag. I'll be interesting to see how this goes.

The idea behind the pre-filter is that it is slipped into bag and the elasticated top of the filter is placed over the mouth of the bag, thus securing it. Twigs, leaves, fine particles and gravel will be trapped in the pre-filter for easy removal from the water. Although this looks to be the least robust part of the kit, it also looks like it could be easily replaced should it tear.

In the top corner of the bag is a large blue plastic grommet for either carrying the bag or hanging it.

collage 2
Clockwise from top left: Pre-filter attached to filler cap. Pur-Blue Process Indicator.
Filler cap is also tethered to the bag. Grommet for hanging or carrying the SolarBag.

A small bottle of 'Pur-blue' process timer was included in the box and this is used to both test how quickly the water reaches a purified state and to indicate that the purification process has finished. The idea is to simply add one drop to the SolarBag and wait for it to disappear. Once the blue has gone, the water is pure. It's not necessary to do this with every fill of water, just when conditions have changed. So, moving to a different area (where the light may be different), having a cloudy day instead of a sunny day, or using a different water source are some of the reasons one would use the Pur-blue solution. It's also a good way of checking that the bag is actually working.

Inside the SolarBag is what looks to be a plastic mesh bag with some kind of filter pad inside the bag. The filter pad is held in place by a number of small plastic tags which look like those used to attach price tags to clothing. I'm guessing this is to stop the filter sagging into a little heap at the bottom of the mesh sack when submerged in water.

Close up of nanotechnology mesh

So, this mesh is the real heart of the SolarBag - it's where all those little nano-thingies sit waiting to pounce on contaminants. Now, there is reams of information about how all this works on the website and, I have to say, it's pretty dry reading. Personally, I'd rather be out in the bush using the SolarBag rather than reading about the science of it so I won't be giving an in-depth scientific review here. The upshot is, we don't have to understand how it works, only trust that is does work. And that's a bit of an issue for me: I confess I'm having a bit of trouble getting my head around the concept of putting water that can potentially make me very ill into a plastic bag, leaving it in the sun for a couple of hours, and then drinking that same water straight from the bag. Normally I would do some kind of penance for my water - pumping till my arm is sore, adding foul tasting chemicals or setting a fire to boil it. That's what's missing here: any kind of interaction or involvement in the process of making this water safe. It feels like I should at least have to stir or shake the contents regularly to ensure all the water has exposure to the nanotech mesh. I can't help but picture all the nasty organisms hiding away in the corners of the bag.
Psychologically, it's challenging to trust that this innocent-looking bag could harbour such force to kill organisms and dismantle chemicals. Still, I'm sure by the end of the test series I will trust it with my life - literally.


The instructions for using the SolarBag are printed in large font on an A-4 size paper. There are some special instructions relating to first time use of the bag which are basically to rinse the bag and pre-filter, then empty the bag. After that, it shows the simple three-step process: fill, purify, drink. The instructions are very clear, concise and made me confident to use the bag. On the reverse side of the instruction page is a "Special Procedures" page which covers off things like how to use the Pur-Blue process timer, how to treat turbid or cloudy water, pre-filter maintenance (hand wash in clean water), and storage of the SolarBag. Despite the complex scientific wizardry going on inside the bag, the instructions are all very simple and easy to understand. Perhaps that's one of the benefits of a product made in the USA - the instructions haven't been translated by someone who doesn't have English as a first language! Again, though, it feels a bit challenging that the process is so darned simple! Surely there must be more? Surely I'm missing something? Nope, it really is as simple as fill the bag with water, place it in the sun and have a nap.

Obviously, the SolarBag is designed to be used stationary and I will be contacting the distributor to see what they recommend for use when hiking. It may be possible to strap the SolarBag to the top of a pack so it's in sunlight while hiking. If that's not recommended, I'd see this more as a base-camp solution. Watch this page for more on this...

The other burning question I have is how this bag will work in a forest. Cloudy days virtually double the treatment time required to around six hours. Does being in a forest have the same effect? Do we have to chase the sun around to keep the bag out of the shadows? I'll be confirming this in my testing but also by contacting the distributor.

Double-sided instruction sheet


Due to constant rain here since my SolarBag arrived, I haven't seen enough sun to test it out yet.
I've got quite a few questions about this water purifier that I'll be attempting to answer during the next four months:
  • Does the bag need to be laid down to work,
  • Does it work if suspended by the grommet,
  • Will it work in the dappled light of a forest,
  • Does it work in cold and rainy weather,
  • How does this product affect the taste of water,
  • Can I store my purified water in the bag or do I need to pour it straight into another container
  • Will the bag work if lashed to the top of a pack
  • Does it need to be kept still or will it work if traveling,
  • And a host of other questions I haven't even thought of yet.

full pic


The Puralytics SolarBag is an ingenious concept with some pretty solid and fascinating science behind it. It's  won a host of awards and promises to be a truly useable solution to finding pure, safe and reliable water anywhere.



June 10-12: Two nights - Stealth Camp, Bruxner Park area near Coffs Harbour, New South Wales, Australia.
Base Camp with short day walks. Partly cloudy. Maximum temps around 23 C (74 F) and minimums around 8 C (46 F). Elevation approximately 100 m (320 ft). Terrain was wet sclerophyl and subtropical rainforest.

July 7-8: One night - Bruxner Park area, Coffs Harbour, New South Wales, Australia. Quick overnight camp. Cloudy and light showers. Maximum temp 14 C (57 F) and minimum 2 C (35 F). Elevation around 300 m (925 ft). Terrain, rocky watercourse surrounded by rainforest.

August 15-16 One night - Station Creek, Yuragir National Park, New South Wales, Australia. Near Sea Level. Sunny and warm. Maximum 27 C (81 F) and minimum 8 C (46 F). Coastal heath and dry sclerophyll forest.

Because I'm carrying some injuries at present, I've been car-based camping so far. However, I have carried my gear in a backpack to approximate loading and pack weights.


This is a very strange product, I have to say. I'm finding it works brilliantly at times but is frustratingly slow at other times. I've achieved the stated three-hour purification time once so far but more commonly, it's been between six and ten hours to remove the blue dye completely. Having said that, removing the indicator dye is a pretty amazing feat - it took more than a week to get the dye off my skin when I accidentally had contact with it.

Perhaps before mentioning how the bag fared, I should mention that I started these tests in mid-winter and the sun is at a low angle in the sky. Generally sunrise is around 0700 (gets to my place around 0800) and sunset is around 1700 hours. Although it has mostly been a mild winter, we have had a couple of very cold snaps (well, cold for a sub-tropical paradise anyway!) which have given us some heavy frosts and temps at, or just below, freezing.

My first test with the Solarbag, I wasn't expecting a lot as the instructions say it may take a bit longer the first couple of uses. I filled the bag with tap water to the very top as I didn't know if having a big air bubble would affect performance. I added a single drop of the indicator dye and after squeezing out the air from the top of the bag I closed the lid tightly. I laid the bag on its side in the sun and started taking photos every hour to compare the progress. As you'll see from the photos, there was not a whole lot of change in colour after six hours when I ran out of day. I emptied the bag and tried again the next day.

Solar test
Images taken each hour from top to bottom. Image at right is after five hours. Although somewhat diminished, there is still a marked blue colour to the water indicating treatment is not yet complete.

Next day I placed the bag in full sun on a glass table but this time I turned the bag so the writing was facing down and not obstructing the nano-mesh. I was astounded to see the bag clear in three hours. I decanted the water to taste it (again, it was tap water), and found it had quite a strong plastic taint.

My next trial involved using filtered water to see whether the taint was because I'd filled the bag from the laundry tap, one I don't generally use much or drink from. I placed the bag in the same location but being a partly cloudy day the dye had not cleared after some eight hours. I left the bag out overnight and another four hours the next day (still partly cloudy) before it was completely clear. At that point I tasted the filtered water and detected a plastic-like taint, but less pronounced.

One of the things I've noticed is that the bag appears to work better after repeated use. It appears to work more quickly when the mesh has been used and is still wet. I've also noticed it can take days to dry the bag out after use. That made me a little concerned about the possibility of mold growing in the bag but there's no sign of that so far. When drying the bag I normally leave it with the opening facing down to allow the residual water to drain for a day then turn the bag so the opening is uppermost and leave it for up to a week to finish drying. That's when I wish the hanging grommet was on the other end of the bag to make it easy to hang while drying, however, a bit of string and some ingenuity allows me to hang it anyway.

I've taken the SolarBag on three trips so far, for a total of four nights. The first two trips were in deep shade in a rainforest environment which stopped the SolarBag working. I was unable to purify a bag of creek water on either trip.

My third trip, to Station Creek, found a nice sunny campsite which allowed me to treat a single bag of water each day.

One of the things I was initially concerned about was how dirty the filter would get if left tethered to the bag. My doubts about this proved to be well founded and I've since detached the filter as it was getting quite dirty from resting on the ground while the bag was being used. The filter certainly seems effective in blocking debris from entering the bag and allows water to flow into the bag remarkably quickly.

Obvious dirt and staining to the outside of the filter after resting on the ground.

I haven't yet used the SolarBag as my primary source of water as my results have been so variable with it. It appears to work brilliantly on hot sunny days with an excellent view of the sky but can become unreliable on cloudy, cool, days or when in the shade of a forest. I was hoping this would also be a useful addition to my preparedness kit in case of flooding but flooding usually happens when it's raining and overcast which is exactly when the bag seems to be least effective. I could see this bag being incredibly useful in places where the weather is hot and sunny but the water is dodgy but I'm less convinced of its application in backpacking. Again, when camping (at least in Australia) we tend to put our tents in the shade to help keep them cool, which is not an ideal environment for the SolarBag. When used with a backpack I've found strapping the full bag across the top of my pack is possible but having that much weight on the top of my pack does tend to unbalance it. Normally, my hydration pack goes in a sleeve in my pack and keeps the weight lower and closer to my back. It's doable with the SolarBag, but less comfortable.

One of the other minor annoyances is that the water tends to be tepid to warm after being in the sun for so long. I've never been a fan of drinking warm water but if my life depended on this it would be a very minor quibble.

I've been storing the water in the bag once it's treated rather than decanting it to another vessel for two reasons. Firstly I didn't want to carry another vessel large enough to decant the water and, secondly, as discussed above the bag seems to work better when it's been kept wet.

As spring approaches in the Southern Hemisphere, the days are lengthening and the sun is climbing higher in the sky. I'm confident this will help the SolarBag reach peak efficiency.


I truly love the concept of the SolarBag and, despite having some very mixed results with it so far, believe it could be a very useful addition to my camping kit. While it can certainly be used for backpacking applications my feeling at this point is that it is best suited to base camping where it can be left to do its thing while I'm out hiking during the day. Placement is crucial - it won't work in deep shade.



I have used the SolarBag on another five occasions at home as I've experimented with how it works.

I've also done a further two camps...

12-14 September: New England National Park, New South Wales, Australia. Two nights, three days. Minimums 7 C (44 F) and maximums 23 C (73 F) in sub-alpine heathland. Grassy, partly shaded campsite. This was a lovely place to camp and, as long as I moved the SolarBag into the sun, it worked quite well taking around four hours to finish purification. Sunny with mild winds

10-11 October: Red Rock National Park, New South Wales, Australia. Two days, one night. Minimums 18 C (64 F), maximums 32 C (90 F). Coastal heath in a defined, grassy campsite. This was a much warmer camp and I managed to purify water from a rainwater tank in around two hours each day. Very hot and humid with minimal wind.


It seems clear to me that the SolarBag is a fine addition to a base camping kit, but not overly practical for actual back packing. It seems to require extended periods of exposure to the sun in cooler months but works better in the warmer months. I'm not certain whether this is because the reactions within the bag work better at warmer temps or whether it's simply the angle of the sun is higher in the sky. The other possibility is that the nanotech has become more active, as it was suggested it would. Either way, as spring has progressed here the efficiency of the bag has increased, provided the day is sunny. Cloudy days, even warm ones, seem to hinder the operation and still require longer periods for complete purification.

Although I've found the SolarBag isn't terribly practical for actual backpacking, it certainly is a useful adjunct to water harvesting methods, provided a source of water can be located. In Australia, that can often be an issue but certainly along the East Coast there are plenty of creeks and waterholes. I must say, though, there is still a psychological barrier to collecting water from some of these sources. Yes, I'll happily collect water from a babbling brook or a small river but I'm still not keen on collecting from those small, stagnant ponds which are full of who knows what! If my life depended on it, I would certainly do it, but honestly, my life doesn't depend on it at present so I'm sticking to 'better' water sources for now. This reluctance and psychological barrier may be completely unnecessary as the SolarBag may be every bit as good as it claims to be, but interestingly, I still can't quite trust it. It seems somehow wrong to simply fill a bag with suspect water, wait a few hours and then drink it. Perhaps the manufacturer could put a few videos on their website showing before and after treatments and people drinking the water to help overcome that psychological barrier? There's currently very little to show the bag in use. I think I've also become habituated to having to do something to my water - pump it, add something to it, boil it, whatever - but there is always a feeling of being actively involved in the treatment process.

The one big issue I've had is in trying to get the SolarBag dry for storage between trips. I normally leave it in the window so it gets some morning sun and enough warmth to evaporate off the residual fluid from the bag but even so, it can take up to two weeks for the bag to be completely dry. It appears the nanotech mesh retains quite a lot of water as I was able to pour small amounts of water out of the bag each day for the first five days. After that, there was condensation in the bag each day after exposure to the sun. Although the nanotech mesh is supposed to kill/neutralize all kinds of things, I was still concerned about developing mould in the bag with such long drying times. So far I haven't seen any evidence of this though.

SolarBag drying on a sunny window ledge. It still took about two weeks to fully dry.

As for signs of wear, I'm pleased to note there really aren't any as yet. I'm pretty careful to treat the bag gently and to make sure I don't put it on any sharp rocks or sticks, but otherwise I've not done anything special to look after it.

In my Initial Report I asked a number of questions about the SolarBag, some of which I now feel I can answer:

  • Does the bag need to be laid down to work? No, it appears to work best if propped so it exposes the full face of the bag to the sun
  • Does it work if suspended by the grommet? Yes, it can be hung to allow it to work, either on a backpack or from a tree.
  • Will it work in the dappled light of a forest. In reality, it doesn't seem to work in any kind of realistic time frame in shade.
  • Does it work in cold and rainy weather? In reality? Not so much. It still works in cold weather, but is less effective. Rainy weather is usually cloudy, which impairs function.
  • How does this product affect the taste of water? There is a definite plastic taste to the water which, although somewhat better after a few uses, is still quite marked.
  • Can I store my purified water in the bag or do I need to pour it straight into another container? It's recommended to pour into another container but can be stored in the bag in the short term.
  • Will the bag work if lashed to the top of a pack? Yes. Although it does affect centre of gravity having 3.5 kg (7.7 lb) on the top of the pack. An alternative is to hang the bag by the grommet on the back of the pack although having that weight sloshing around is also unbalancing. It would be good to have a second grommet to make it easier to attach to packs.
  • Does it need to be kept still or will it work if traveling? It works fine when walking as sunlight is the key element here.


In summary, the SolarBag is an exciting concept which will have application in many countries and scenarios. It's a brilliant addition to an emergency preparedness kit and is being successfully used to treat water in many Third World countries. For backpacking, though, I see some limitations. Firstly, I normally try to set up camp under a shady tree, which reduces the efficacy of the purifier unless the bag is moved into full sun. Secondly, the bag is cumbersome when used with a backpack. It has to be attached externally to work. Thirdly, It's really difficult to dry between uses when looking to store it.

Apart from those issues, the SolarBag does produce very, very safe drinking water with minimum fuss: no batteries required! Although I've only been able to get it to work in the advertised two hours a couple of times, it still appears to be a fairly reliable option, especially in sunny climates.

To me, this is a great option for base camping rather than backpacking and, as such, will find a place in my car-camping kit as there are so many waterborne diseases around nowadays. The SolarBag can give me water of a purity higher than almost every other option, all with minimum effort on my part. After all, I go camping to relax.

That concludes my Long Term Report on the SolarBag and I'm thrilled to have been a part of this test series. I'd like to thank Puralytics and for the opportunity to be a part of this test series.

Read more gear reviews by Kerri Larkin

Reviews > Water Treatment > Solar > Test Report by Kerri Larkin

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