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Simply put, gravity water filters are filters that use only the force of gravity to draw water through one or more filter stages. This means they work without the need for electricity or water pressure.
While they utilize a simple design, there is a lot to learn about how these filters operate.
Let’s take an in-depth look at how a gravity water filter works, and whether you should consider one for your filtration needs.
Gravity water filters are simple filter systems that utilize the force of gravity to filter water from an upper chamber through one or more filter elements and then onto a lower chamber for storage – much like a water filter pitcher!
As the name suggests, these filters only use the force of gravity to operate, eliminating the need for electric pumps, boosters, and even a plumbing connection.
The rudimentary design has an upper chamber sitting directly on top of the lower chamber, with one or more filter stages sandwiched in between. Water is poured directly into the upper chamber, where it slowly passes through the filter(s) before collecting in the lower chamber ready for use.
The filter elements are the most important elements of any gravity filter. These are the heart of the filter system and determine which contaminants will be removed from your water.
What’s great about some gravity water filters is that they combine different filtering media/methods. For example, we often find filter elements with an outer shell made from ceramic and a core filled with ion exchange resin and activated carbon. This provides for the broadest reduction of water contaminants almost regardless of type.
The most common type of gravity-based water filter is the countertop system. These filters are typically made of stainless steel or ceramic, or plastic for lower-end units. They are relatively large and bulky so they’re suited for indoor use rather than portability.
These filters typically sit on a kitchen countertop and filter tap or well supplied water.
The other major category of gravity-based filters is gravity bags and bladder filters. These filters are specifically designed with camping, hiking, and off-grid use in mind, and can be rolled up into a compact bundle when not in use.
While countertop units vary in terms of which contaminants they eliminate, gravity bags mainly use microfiltration or nanofiltration to remove potentially harmful microorganisms from water sources. Most have a rubber-like bladder designed to be hung from a tree as it filters water from local streams, lakes, or rivers.
One of the big pluses of any gravity system is its ease of installation. All that’s needed to set one up is to unpack the box, assemble the system on a counter, prime the filter elements, fill the upper chamber with water, and wait as the system filters your water.
If you compare this with other water filtration systems, which require complex installation involving plumbing and/or electrical hookups, gravity systems have a distinct advantage.
Another major advantage of gravity systems are their relatively low cost. While it’s true that higher-end units will run you $300 or more when you take into consideration the cost of ongoing maintenance you’ll quickly find that gravity units cost less over time.
Gravity filter maintenance is exceptionally simple when compared with other filtration systems. All that’s needed is cleaning or replacing the filter elements periodically and occasionally cleaning the tank to keep it sterile.
Gravity-based water filters have the advantage of working without the need for electricity or a plumbing hookup. This makes them ideal for off-grid use or for catastrophe-type scenarios where you could lose access to these utilities. In a situation like that, as long as you have access to a freshwater source, you’ll be able to use your gravity filter.
While most water filtration systems are supplied directly via your home’s plumbing, gravity-based systems must be filled manually by pouring water into the upper chamber. This isn’t the biggest issue in the world for most people, but it is slightly less convenient than simply opening a faucet.
The exact level of purification will depend on the specific gravity filter in question, however, in general, gravity filters don’t always achieve quite the same level of filtration as advanced systems like reverse osmosis.
There’s no getting around the fact that gravity-based water filters take a long time to filter water. This is due to the system being powered only by gravity, so there is no external pressure to push the water through the filter faster.
A typical system can take 45 minutes or more to fill, so if this sounds like a dealbreaker to you, you might want to consider an alternate filtration system.
You might be wondering if gravity water filters are safe and good for your health.
The answer to this will depend on the specific model and its filtration capabilities, as well as the contaminants you are dealing with in your feed water. The most important thing to consider when it comes to acute safety is ensuring the water is free of potentially harmful bacteria, viruses, and cysts.
Water supplied by a municipal source almost always be free of these issues in the first place. If you’re camping or hiking and need to drink water from a questionable source, then a good gravity filter bag/bladder will remove these contaminants. Higher-end countertop units using a ceramic filter will also accomplish this, which is especially important if your water is supplied by a well, which are more prone to this type of contamination.
If you’re concerned about your home’s municipally supplied water, then it’s a good idea to get your water tested to see what contaminants it contains. This will enable you to choose a filter that’s tailored to remove the specific impurities you’re dealing with.
If you’re talking in general though, gravity-based systems are safe and highly effective. They have the advantage of a longer contact time between the filter elements and the water, which leads to a thorough filtration process.
When it comes to bacterial removal, higher-end countertop units can typically handle this.
The precise effectiveness of a given filter against bacteria will depend on its micron rating – which is a measurement of the pore size in the filter. If it’s above 1 micron or so, it will allow bacteria to pass through – as most common bacteria measure 1 to 2 microns in size. Smaller ratings in the .1 micron size will eliminate virtually all pathogenetic bacteria and parasites.
Many bag/bladder type filters are specifically designed with this goal in mind, so they excess at eliminating microbial contamination from questionable water sources.
At this point hopefully, you have a solid grasp of the strengths and weaknesses of gravity-based systems.
To give a general answer, gravity systems make an ideal option when you’re looking for a low-cost, low-maintenance, emergency-friendly filter that doesn’t require either electricity or a plumbing hookup to operate.
If you want a filter that provides instant water on tap without waiting, doesn’t require manual refilling, and provides the absolute best filtration level, then you’ll want to look elsewhere.
Here is what to consider when buying a gravity water purifier:
Before you invest in any gravity-based water filter system, you’ll want to determine where you plan to use it. If you’re planning on using it as a home unit, then a countertop unit makes sense.
Alternatively, if you’re looking for a filter for camping, outdoor excursions, and off-grid use, then a filter bladder or bag is the way to go. These units are specifically designed with the outdoors enthusiast in mind, meaning they’re lightweight, collapsible, and designed to remove microbial contamination from freshwater sources.
Another thing to consider when shopping for a gravity filter is the filter’s effectiveness and what contaminants it will remove.
Before you choose a particular filter, it pays to get your home’s water professionally tested to see what you’re dealing with. Once you have the test results, you’ll be able to make a far more educated purchase than simply guessing and picking a random filter.
When choosing a system, you’ll want to pay attention to its NSF certifications (or testing). If you purchase a filter without any NSF standards behind it, then you’ll have no way of knowing the truth of the manufacturer’s filtration claims.
Water flow rate refers to the speed at which water poured into the upper chamber passes through the filter and onto the lower chamber. A typical system will take 45+ minutes to filter an entire chamber, so you’ll need to wait for some time even if you have a higher-end filter.
Generally, larger high-capacity units have a better flow rate than smaller-capacity units, but this is not always the case.
Also, don’t confuse a faster flow rate with a better filter. The reason gravity filters are so effective in the first place is the extended period of contact between the filter and the water.
If you’re looking for portability in a gravity filter then you’ll want to take a good look at gravity bags/bladders. These units are built for maximum portability – making them the ideal choice for camping, hiking, or any outdoor excursion.
Most countertop units aren’t exactly portable and tend to be rather large and bulky. If you’re interested in a countertop unit, then it generally makes sense to go with the largest unit you can fit and afford. This will give you enough capacity that you won’t need to constantly refill the system, plus larger units tend to have a faster flow rate as they can hold more than one filter element.
Storage capacity refers to how much water the system can hold in its tanks when filled. Gravity filters come in a wide range of sizes, so it isn’t difficult to find that one’s suited to your needs.
If you’re looking for a unit suited to 1 to 3 people, then a 1 ½ gallon tank makes sense. 2 ½ gallon tanks are ideal for a family of 4, while larger 4 to 6 gallon tanks can supply between 6 and 12 people.
If you’re not sure exactly what sized tank you’ll need, it makes sense to go one size bigger than you think you might need. Having more capacity than you need is not a problem, however too small of a tank means you’ll be constantly refilling, which can get tiring quickly.
Filter life refers to the lifespan of the filter before it needs replacement. Higher-end filters tend to have longer lives than lower-end ones, which helps to justify their higher price point.
Better countertop units tend to use inert materials like ceramic and stainless steel. These materials won’t degrade over time and do not leach into your water, so you can be sure your filtered water remains pure.
Cheaper filter systems tend to use plastic, which even if rated BPA-free can potentially leach into your water.
Most gravity water filters use the same basic design, so there’s not that much to consider here. However, you want to make sure the filters are easy to change and the spigot is at a comfortable height.
If you have any questions about gravity filters in water treatment please don’t hesitate to leave a comment below!
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