Safe Drinking Water

As summer returns slowly to our lives with all the beauty and delight of a long-lost lover, our thoughts move to hydration on the trails. Well also late, muggy evenings beneath the stars, beach runs and holidays… but hydration on the trails is up there with our summer dreaming! Carrying sufficient drinking water from the beginning of your run is critical, but what happens when you run dry? We interviewed some environmental experts to find out more on what to avoid, and when it’s safe to drink your fill.

Brigitte Melly is an avid trail runner, as well as a wetland ecologist working for a research organisation in Cape Town. We asked her about most important things to look out for when choosing safe drinking water in the mountains or on trails.

“Carry out a normal visual check - litter, smells, strange colours are a no no. Check for evidence of life in the river (fish, plants, even some algae growing from the base is good!). Look at proximity to informal settlements, the further away the better. Also, check how close it is to the source (higher up is better). The faster the flow, the better, and always choose water above rather than below the path you are on. Local knowledge is key, so check with those around you.”

What are the risks?                                                                                                                   

“Cholera, dysentery and typhoid. In addition, bilharzia can be contract from being in the water (eastern flowing rivers).”

Can you test the water on your local trails?

“Theoretically you can take a sample and send it to your nearest lab or university. But there are standards and protocols that need to be upheld to take a good sample. It is much easier to ask around, or phone the nearest university and one of the environmental science departments (botany, zoology, geography, hydrology) should be able to tell you who has sampled / worked there and when was the last time it was checked. Local municipal offices or conservation organisations can also help (e.g. Cape Nature, SANParks).”

Brigitte recommends carrying a filter straw - specifically the Sawyer Mini filter straw. “It's small, light and has got me through the fish river canyon with no problems at all! Best thing is that you get to drink nice tasting filtered water, straight away rather than chemically laden water (drops and tablets) which you can only drink after a waiting period.”


Rob van Hille describes himself as an “enthusiastic, if infrequent trail runner with five PUFfeRs under the belt”. He studied microbiology and zoology, then a PhD in Biotechnology.  Rob spent 12 years doing research in Bioprocess Engineering at UCT, mainly looking at industrial and mining water treatment.

“There are no absolutes in terms of deciding whether water is safe or not.  Easier to understand the risks first.  There are two main sources of concern.  The most common is bacteria, viruses or protozoa (Cryptosporidium and Giardia), while toxic metals or compounds leached from poisonous plants are less common.  The primary sources of bacteria, viruses and protozoa that can cause illness are from human or animal faecal matter, so if there is any indication of this (smell, visible faeces close to the stream, evidence of significant animal activity) avoid drinking.  If the water is stagnant or slow flowing the chances of high bacterial numbers increases, as they can proliferate in the relatively confined space.  Fast flowing water has a lower risk.  Water from a spring is less likely to have microbial contamination than surface water, although groundwater can still have high levels of bacteria.  I have tested a lot of borehole water around Cape Town over the last year and have seen everything from no bacteria to very high concentrations.  Most of the pathogenic microbes will result in symptoms of nausea, diarrhoea and cramps.”

Rob’s advice, ultimately, is to carry your own water on the trails, unless local knowledge indicates a total lack of risk.

“From a water treatment perspective, there are two broad categories: filtration or chemical treatment and there are different forms of both. Filtration devices, like Lifestraw or the tea bag filter (developed by Stellenbosch University), make use of size exclusion to remove bacteria and protozoa (pore sizes are typically less than 2 µm).  Most viruses are small enough to pass through the filters.  The filters don’t remove anything in solution, like toxic heavy metals (e.g. Lead etc) or metalloids (e.g. Aresenic), but some will include activated carbon or nano fibre polymers that can remove metals and soluble organics.

Chemical treatment normally involves adding a strong oxidant (chlorine, bleach or chlorine dioxide) or an antimicrobial agent (iodine). These can come in tablet or liquid form.  They are generally very effective against bacteria and viruses, but less effective against protozoans, which form resistant cysts as part of their life cycle.  Most infections are through cyst ingestion, with germination to the adult form later.

You can collect water from a specific spot on the mountain and have it tested in a laboratory, which will give you a comprehensive analysis, but there is no guarantee that a contamination event won’t happen the next day.

You’re still safest taking your own water with you, but if not a filtration device that includes both size exclusion and adsorbent material (activated carbon or nano fibres) is advised.”

Gear suggestions:

The Lifestraw Water Purifier filters a minimum of 1000 liters per unit. It removes 99% of waterborne bacteria and waterborne viruses. It removes particles down to 0.2 micron. Purchase here.

The Sawyer Mini Filtration Kit filters bacteria such as salmonella, cholera and e.coli as well as protozoa and cysts. Purchase here.