Water purifier review

If you often go on long day or multi-day tours, you know the problem: you need enough drinking water, but don't want to carry too much because of the weight. Water purifiers can help here. You can use them to filter water on the road and replenish your supplies. We have tried out two different water purifiers from MSR and GRAYL and explain how they work and what the differences are.

MSR Guardian Purifier: The pump water purifier

The name of the brand MSR stands for Mountain Safety Research - and that is exactly what the products are all about. The MSR Guardian Purifier was originally developed for the troops of the US military. Accordingly, the quality is very high.

The water purifier filters out viruses, bacteria, protozoa and sediments even from extremely contaminated water. This makes it suitable for use in developing countries and wildlife areas. The filter complies with the NSF standard P284 of the US military. This is the strictest standard for water filters in the USA. It is now also available for hikers and globetrotters. The Guardian Purifier comes with a practical bag in which it can be packed for tours.

>> Get the MSR Guardian Purifier

How to filter water with the Guardian Purifier

The Guardian Purifier works like a pump. To filter water, first unscrew the red lid from the bottom of the Purifier and then place the hose in the water. The pre-filter, which is held by the foam float just below the surface of the water, where the water is cleanest, already keeps out coarse dirt.

Using the lever, you pump the dirty water into the Guardian, where it is cleaned in the hollow fibre filter. The clean drinking water comes through the opening at the bottom. If you have a drinking bottle with a suitable thread, you can screw it directly onto the Purifier. Since the water is pumped out of the filter in a thin stream, you can also simply hold it over the opening of any bottle or cup and fill it that way.

The pump mechanism works easily and quickly. Around 2.5 litres of water can be pumped per minute. The Purifier is also self-cleaning. With each pump burst, it rinses out the impurities in the water. The hollow-fibre filter cartridges are extremely durable and can purify up to 10,000 litres of water before they need to be changed.

>> MSR Guardian Filter Cartridge Replacement

GRAYL GeoPress Purifier Bottle: The drinking bottle with filter

The GeoPress Purifier Bottle by GRAYL is drinking bottle and water filter in one. For the filter, GRAYL uses ion exchange and ultra-powdered activated carbon to filter chemicals, pesticides, heavy metals and waterborne pathogens from water. This includes 99.99% of viruses, bacteria and protozoan cysts. The filter complies with NSF standards 42 and 53. 

>> Get the GRAYL GeoPress Purifier Bottle

The GeoPress bottle has a volume of 710 millilitres (24 oz). Depending on the backpack, the purifier fits into the side pockets for drinking bottles. Alternatively, it can simply be attached to the backpack using the handle on the lid. If you prefer a more compact bottle, GRAYL offers the smaller UltraPress Purifier Bottle in addition to the GeoPress. It works with the same system, but only has a capacity of 0.5 litres and is therefore somewhat smaller. Both versions are available in different colours.

How to filter water with the GeoPress Purifier Bottle

The GeoPress bottle consists of an outer container and the transparent inner bottle to which the filter cartridge is attached. To filter water, remove the outer part, fill it with water up to the mark and place it on a flat surface. Then simply press the inner bottle with the filter into the container. To allow the air in the bottle to escape, the SimpleVent cap, i.e. the drinking cap, must be twisted open half a turn. The pressing process takes about eight seconds. At the end, the filtered water is in the inner bottle and can be drunk directly from the Purifier Bottle.

The rubber rim on the bottom of the bottle ensures that it does not slip away during the pressing process. Rubberised, non-slip surfaces are also incorporated on the sides of the bottle for a better grip. Ergonomic comfort pads on the lid make pressing more comfortable. 

How long the filter can be used depends on how dirty the water is. Generally, it is designed for around 350 cycles. When it becomes difficult to press down and the pressing time reaches 25 seconds, it is time to replace the cartridge.

>> Replacement filter cartridge for the GeoPress Purifier Bottle

Comparing MSR and GRAYL

Whether from murky lakes, rivers and wells, hotel sinks or other taps, both manufacturers promise safe, clean drinking water worldwide and offer tested water filters according to the NSF standard, whereby the Purifier from MSR even meets the stricter P248 standard.

A practical advantage of the MSR Guardian Purifier is the hose. With this, water sources that are more difficult to access or particularly shallow can also be used. The GRAYL GeoPress Purifier Bottle has more difficulties here, as it has to be immersed a little deeper to be filled.

The advantage with GRAYL is that it also functions as a drinking bottle. So you can drink the filtered water directly from the Purifier or store it for later. The Guardian requires a separate bottle, which is not included with the Purifier. It can only be screwed on if the thread fits. 

Both purifiers proved convincing to us. In the end, it is up to you to decide which features are most important to you, where and how you want to use the water filter and how much you are willing to spend.