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Gravity water filters are one of the oldest and simplest water filtration methods out there – but that doesn’t mean they aren’t effective. As you might expect from their name, these filters use the force of gravity to draw water through one or more filtration stages.
The major advantage of a gravity-based filter is its ability to operate without the need for electricity. They also don’t require any plumbing connection, so they’re great for camping, traveling, and other remote uses.
Let’s take a closer look at how a gravity water filter works, and when you should consider using one for your filtration needs.
So, how does a gravity water filter work?
Gravity water filters are simple filter systems that utilize the force of gravity to filter water from an upper chamber, through one or more filtration stages, and then into a lower chamber. The simplified design avoids the need for electric pumps, boosters, and even a plumbing connection.
The basic design features an upper chamber sitting on top of a lower chamber with filter stage(s) positioned between the two. Water is poured into the upper chamber where it slowly works its way through the filter stage(s) and into the lower chamber where the filtered water is stored for use.
The most important component of any gravity water filter is the filter or filters between the two chambers. The filter element is what determines which contaminants will be removed from your feed water.
A gravity water filter is any system that uses gravity to force feed water through a filter so it doesn’t need pressure or electricity to operate.
This is a fairly broad definition and encompasses a range of filter types.
The two major gravity filter subcategories are countertop gravity filters, and filter bladders and bags. There are also pitcher-style gravity filters, but these operate similarly to countertop filters.
Countertop gravity filters are typically made from ceramic, stainless steel, or sometimes plastic, and sit on a kitchen countertop. They are relatively large and high-capacity, so they are ideal for indoor use. Most are used to filter tap or well supplied water at home.
These filters can also be used for camping or traveling, but their large size makes them less suited to this than filter bladders and bags.
Gravity filter bladders and bags are ideal for hiking and camping usage. These filters can be flattened and rolled up into a compact bundle when not in use, so they’re easy to fit in a backpack or suitcase.
These filters are typically designed to be hung from a tree or something similar. They utilize various levels of microfiltration or nanofiltration to remove potentially harmful microorganisms from unsafe water sources like rivers, lakes, and creeks. These filters are a great item to have with you on any excursion, as you never know when you might need to drink water from a non-potable source in an emergency.
Let’s take a look at some of the pros and cons of gravity water systems to help you decide if they might be right for you.
One of the major benefits of a gravity water filtration system is that zero installation is required to get one set up. All that’s needed is to unpack the box, set it up on the counter, fill the upper chamber with water, and let the filter do its thing.
If you contrast that with reverse osmosis or UV filters, which require special installation with plumbing and/or electrical hookups, the gravity system is a clear winner.
Gravity systems don’t require pumps or boosters to operate, which means no electricity is needed. This makes them great for off-grid use and camping, as well as just making them simple to use.
Another big plus for gravity filters is their low price point. A typical countertop gravity unit will run you between $100 and $350, which may sound like a lot, but when you consider the ongoing maintenance and filter costs are very low it makes gravity filters an attractive option.
Gravity-fed water filter maintenance is exceptionally simple when compared with other filtration methods. All that’s needed is occasionally re-priming or changing the filter elements and cleaning the water tank from time to time.
Another pro for gravity filter units is their versatility in an emergency scenario. In a real catastrophe situation, where you don’t have access to electricity or working plumbing, you’ll still be able to use your gravity filter with a freshwater source to make clean, potable water.
While most water filter systems are hooked into your home’s water supply, gravity-fed filters must be manually refilled by pouring water into the upper chamber. This is slightly less convenient than simply opening a faucet with filtered water coming out.
This one will depend somewhat on the type of filter you have, but in general gravity water filters don’t achieve the same level of filtration as some more advanced water purification methods like RO.
When you pour unfiltered water into the upper chamber, you’ll notice that it can take quite a while for it to filter all the way through the element(s) and into the lower chamber. This is because the water isn’t pressurized, so the filter only has the force of gravity to push water through the system. On the plus side, most gravity filters have large enough chambers that you won’t need to refill them constantly.
The answer to this will depend on the specific filter in question, and the contaminants you’re dealing with. As far as health and safety are concerned, the most important thing to consider short-term is ensuring your water is free of potentially harmful microorganisms like bacteria and cysts.
Generally, water supplied by a municipal source will be chemically treated and free of these contaminants in the first place. However, if you’re camping or on an outdoor excursion, and you’re sourcing water from a questionable source, then a good gravity filter bladder/bag will remove these contaminants. The same goes for water sourced from a well, which can have issues with microbial contamination as well.
If you are referring to water at home, then it’s a good idea to get your water tested to determine exactly what contaminants it contains. Then you can base your filter choice on which model will eliminate the contaminants in question.
In general, though, gravity water systems are effective and safe to use. These systems have the advantage of a longer contact time between the water and filter elements, which leads to highly effective contaminant reduction.
When it comes to bacterial removal, most higher-end countertop units will remove the vast majority of these contaminants. The exact effectiveness will depend on the filter’s micron rating.
Gravity bags and bladders are specifically designed with this purpose in mind and are nearly completely effective at removing bacteria, viruses, and cysts from any water source.
By now you should have a good idea of the strengths and weaknesses of gravity-based water purifiers.
To put a finer point on it, gravity-based water purifiers excel when you want a low-cost filter that’s easy to set up, easy to maintain, don’t require electricity or plumbing to operate, and will work well in off-grid or emergencies. They aren’t so good if you don’t care to wait for the water to filter, if you want the absolute highest level of filtration, or if you don’t want to manually refill the chamber.
This is a major one, as it will determine the type of gravity-based water system you’ll need. If you’re looking for a home unit to use with your tap or well supplied water, then you’ll want to go with a countertop unit.
On the other hand, if you’re looking for a unit for camping, backpacking, or off-grid use, then you’ll want to go with a gravity water filter bladder or bag. These units are light, collapsible, and designed specifically for use with non-potable water sources like lakes, creeks, and rivers.
Another major point to consider when shopping for a gravity water filter is which contaminants you’ll need to remove. Of course, the best thing you can do to determine which contaminants will need removing is to get your water source professionally tested.
After testing you’ll have a precise reading of what’s in your water and can tailor your filter purchase to your results.
As mentioned previously, the contaminants removed will depend on the filter element and micron rating in your filter. Oftentimes, higher-end filters will remove a higher percentage of contaminants than cheaper ones will.
Flow rate refers to how quickly water flows through the filter into the lower chamber. Gravity filters are notoriously slow at filtering water, so if waiting for water to filter through the system is a problem for you, then you might want to consider another filter type.
A typical gravity system will take 45+ minutes to fill an entire tank, so keep this in mind when purchasing. Also, smaller units often have a slower filtration speed than larger units.
When it comes to portability, countertop units are relatively large and bulky, so they aren’t exactly portable. Generally, when you’re shopping for a countertop unit, it makes sense to go for the largest unit you can fit/afford.
Filter bags and bladders, on the other hand, are extremely portable, making them ideal for backpacking and camping excursions.
If portability is important to you, then you’ll want to go with a filter bag unit instead of a countertop unit.
Another important consideration when shopping for a gravity filter is its storage capacity. These filters come in a range of tank sizes, so you can find one ideally suited to you and your family’s needs.
Units in the 2 ½ gallon range are ideal for a family of four, while larger 4 to 6 gallon units are great for 6 to 12 people. Smaller units in the 1 ½ gallon range are suited for 1 to 3 people.
Filter life generally varies based on filter quality. Higher-end filters can last up to 3,000 gallons or 3 years of use, whereas lower-end filters may only last 100 gallons or so.
Higher-end gravity water filters tend to use better materials like food-grade stainless steel or ceramic. Cheaper units tend towards plastic, which even if free from BPA can have issues with leaching.
Lastly, you want to look for a system that’s easy to use and simple to maintain. Most gravity filters utilize the same basic design, so there isn’t that much to consider here other than how easy it is to change filters.
If you have any thoughts about the question, how does a gravity-based water purifier work, please don’t hesitate to leave a comment below!
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