How Does A Gravity Water Filter Work [Videos]

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So, how do gravity-fed filters work? A gravity water filter uses the pulling force of gravity to move water from the unfiltered reservoir, through the filter, and out the bottom into a storage container. 

While the water is being moved down, particles are being stopped and filtered to provide clean drinking water. Most importantly, gravity filter systems do a great job of cleaning water and making it safe to drink.

The best gravity water filters provide clean drinking water efficiently. The Platypus GravityWorks system is one of the best. Knowing how they work will give you a great idea of what to buy and what will work best.

Woman sitting on the rocks in the mountains overlooking a lake with a gravity fed water filter on the nearby rocks

How Effective are Gravity Water Filters?

Gravity water filters are very effective in creating safe-to-drink water. There is no pumping involved, as gravity takes over and does the real work. When you combine water, gravity, and a high-quality filter together, you get drinkable water.

Although usually pretty slow, gravity water filters do a great job of removing contaminants. When the water moves from the first hang bag to another or a different type of container, the magic happens in-between. That is where the cleaning and filtering process takes place. So, you will have to wait a bit, but gravity does a great job of really getting everything out during that time.

The Platypus GravityWorks filter is one of the fastest of the slow filtering gravity filters on the market. It delivers four liters of filtered water for drinking and cooking in under two and a half minutes.

A man carrying a gravity water filter in the mountains

Do Gravity Water Filters Remove Bacteria?

The type and quality of your gravity water filter will determine exactly what can be filtered out. The lower-level gravity water filters will focus on chlorine and physical pieces being filtered out. Once you go for the more expensive and high-quality filters, you will be able to filter out more contaminants.

RELATED ARTICLE: How to Purify Water When Backpacking

Water contaminants include many things such as bacteria, protozoa, pesticides, heavy metals, and more. For example, if you look at the Platypus GravityWorks, it removes 99.9999% of bacteria. In addition, it removes 99.9% of protozoa, including giardia, cryptosporidium, E. coli, salmonella, and cholera. No filter removes 100%, so this is about as good as it can get.

Again, removing bacteria is not something that happens with every gravity water filter. But, it is very important to consider bacteria. According to the Minnesota Department of Health, water with bacteria and other pathogens can make you sick. Also, you cannot test the water every time before you drink it. This is where a gravity water filter can come in and save the day.

Pros and Cons of Gravity Water Filtering

Platypus Gravity Fed Water Filter hanging in a tree in the mountains.

With any purchase, there are pros and cons. So, here are the pros and cons of buying and using a gravity water filter!


  • Super easy to use

  • Bags Come in Different Sizes

  • Eliminates  Majority of Pathogens 


  • Requires Maintenance

  • Slow to Filter

The biggest and best pro is the ease of use. These are super easy to set up and use, which is a really good aspect of your purchase. 

You should probably give it a trial run at home before hitting the trail so you can have an idea of how it works.

Gravity water filters have one bag that is high and another that is low. The in-between portion does all the work. So all you have to do is manage the water going in and coming out, which is very easy.

One of the most common times you would use a gravity water filter is when hiking or backpacking. 

In both of these cases, weight is an important aspect. Luckily, these filters are very backpacker-friendly. They weigh 11.5 oz and are quite light. 

Now, if you want to conserve on weight even further, you can opt for larger or smaller hang bags depending on your needs and space requirements.

Do Gravity Water Filters Filter Pathogens?

Like we have already talked about, gravity water filters can filter out a vast majority of pathogens found naturally in water. 

This is a big deal. 

You do not have to use chlorine or iodine tablets to disinfect the water. Both can give your water an unpleasant taste.

When bacteria and other pathogenic substances are in the water, you can become sick very quickly. When you know your water is clean, that is one less stress to worry about.

With any device that has a filter, there is some maintenance involved. Although it is not usually a big deal, it is still something to consider.

Recontamination is a big deal when using water filters. Therefore, you need to ensure that the water being cleaned is happening efficiently and safely. 

The filter needs cleaning out regularly, and the water lines also need to be cleaned. This ensures that the water being filtered is still safe to drink.

Drawback of Gravity Water Filters 

The biggest drawback of a gravity water filter is the speed at which the water is filtered. Because gravity is doing the job, you cannot do anything to quicken the process. 

This is a slow part of the process, so it is important to be patient. If you are not in a big hurry, then this is not a huge issue.

In addition, dirt and other organic particles suspended in water will clog the filter over time. This slows filtering efficiency even further. 

Most gravity systems include a plunger syringe to backflush the filter in the field. Most importantly, make sure to fill the plunger with filtered water before backflushing. You don’t want to contaminate the clean end of the filter.

Finally, it is stressful if you are already low on water and need to replenish quickly. A high-capacity filter will efficiently clean water in a much shorter time.

Which Gravity Water Filter is Best for Hiking?

Hands down, the best gravity water filter for hiking and camping is the Platypus GravityWorks High-Capacity water filter. This is a hanging bag filter that does a great job of filtering water cleanly and efficiently.

First and foremost, filtering is the best in the business. We will talk about other factors shortly, but you need a water filter that does its job well. The Platypus does its job very well.

They claim to filter out 99.9999% of bacteria and 99.9% of protozoa, so you are covered on that end. This is important to consider because not all hang bags can do this.

One of the other big factors is weight and capacity. This is a very lightweight gravity water filter that can be compacted down easily. 

So, for those hiking and backpacking trips, you do not have to worry about the filter being too heavy.

In terms of capacity, this bag holds four liters of water at any one time. 

Once you filter one bag, you can empty the clean water into another container, refill the bag, and start the filtering process over. 

This is big enough to filter water for yourself or larger groups on the trail. 

So, all you have to do is fill the bag, make sure everything is connected correctly, and hang it in a tree. After that, it is simply waiting for your water to be potable.

To beginners, the price may be a little scary because there are cheaper options out there. 

However, a good filtering system is truly an investment. When you spend hard-earned money on something like this, you want to get the maximum value possible from your purchase. You get that with this option.

You can also find the Platypus GravityWorks system at REI.


 How do you hang a water bladder for a gravity filter?

Gravity water filters are meant to be hung from something like a tree or some other piece of structure to pull the water down through the filter. Simply hang the top bag to a tree or other high place and affix the second bag in a lower section. When you complete the setup with the line and filters in between, you are good to go.

How do I clean a gravity water filter?

Three main components need to be cleaned: The hang bags, hose, and filter. All three of these need to be clean for the water to be properly filtered.

One great way to clean the system is backflushing. This is when you use clean water and run it in the opposite direction through the filtering system. When the water runs the other way, it can clean the filter from the bigger chunks that can get stuck. The Platypus GravityWorks system includes a plunger syringe that is filled with clean water and pushed back through the filter from the clean waterside.

To fully clean the filter, clean it out with water and a little bit of bleach to kill any remaining pathogens.

 How often do you have to replace a gravity-fed water filter?

The two main factors that determine when a filter needs to be replaced are the volume of water being filtered and how dirty that water is. When you are filtering pretty clean water, you can go 1500-1600 liters before switching out the filter. If the water is dirtier, the lifespan drops to 1000-1100 liters.

Therefore, you must monitor how much water has been filtered. If you continue filtering water with an old filter, your clean water may be contaminated.


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