How a gravity filter works
The operation of a gravity filter is based on the physical theory of gravitational attraction. This force acts on all bodies on Earth, giving them weight and drawing them towards its centre. Water in a gravity filter undergoes the same phenomenon. This is what allows it to be ‘pushed’ and pass through the filter to be purified.
Composition of a gravity water filtration system
A gravity water filtration system consists of two tanks, a tap, filters and any additional accessories.
The two tanks, usually made of stainless steel, are nested inside each other. The upper tank contains the filters and will receive the water to be filtered. The lower tank is fitted with a tap to allow the filtered water to be used.
Several models are often available, depending on the volume of the tanks and the number of filters that can be installed.
The Star Water Filter® range
Our range of gravity-fed water filters includes three models. Mini Star, with a capacity of 5.6 litres, Big Star, with a capacity of 8.5 litres and Super Star, with a capacity of 12.3 litres.
Each model is available in a stainless steel, black lacquer or creamy white finish, and all three are fitted with two Ultimate Star Filters® as standard.
The 8- and 12-litre models can be fitted with four filters to speed up filtration.
The choice of model depends on the amount of water you intend to use and the number of people who will be using the system. Our buying guide will help you choose the right model for your intended use.
There are two types of tap. A stainless steel tap, included as standard in the basic price, is supplied with every system. However, there is also an optional level tap that allows you to read the level of filtered water in the lower tank directly.
Using the gravity filter
Using a gravity water filtration system is very simple and requires very little maintenance. No work is required to install it, and you don't need electricity or water pressure from your mains supply.
The upper tank is filled with the water to be filtered, which, pushed by gravity, passes through the filters. The water is then purified and stored in the lower tank for consumption.
For further information, please consult the installation and maintenance instructions.
The filtration element
The filter is the key component of a gravity-fed water filtration system. In fact, the quality of the filtered water depends directly on the quality of manufacture and design of the filter.
It can be made from activated carbon only, as is often the case, or from a more elaborate design that provides much more effective filtration. For further explanation, you can read how our filter was designed, and if you want to choose your water filter with some sound advice, check out how to choose your water filter from the various brands on offer.
Advantages of a gravity water filtration system
A gravity filter is highly effective against many pollutants (if the filter is well designed), is easy to use, requires little maintenance and is economical.
Above all, it's a totally autonomous filtration system, requiring no electricity or water pressure, unlike osmosis systems or other under-sink filtration systems, for example. Finally, it's ecological and economical, costing around 2 centimes per litre filtered.
Information, advice and tips
- To choose the right filter volume for your application, see our advice in the buying guide.
- Although our filters are designed to last longer, we recommend changing them after using 6,000 litres of water (for a pair of filters). Be wary of filters that guarantee exorbitant filtration volumes, especially if they are made only of activated carbon. See our advice on choosing a gravity filter.
- Filtration speed varies according to the height of water in the upper tank. This is a normal phenomenon due to the pressure of the water column on the filter. The less water there is, the lower the pressure and the longer the filtration time.
- Due to insufficient pressure caused by the very low water column when the upper tank is almost empty, some unfiltered water remains in the upper tank, and this is normal. This water will be mixed at the next refill and filtered before being consumed.
- To ensure that your system operates optimally, the upper tank must be filled regularly and completely. Similarly, you should not fill the upper tank if there is still water in the lower tank, otherwise there will be an overflow between the two tanks. See our advice on how to use your gravity water filtration system.
- The filtered water should be consumed within 2 to 3 days.
- The more a filter is used, the more its flow rate decreases because of the pollutants, sediment and limescale that settle on its periphery and block the filter's micro-channels. Regular cleaning (see maintenance instructions) will restore the flow rate to normal. However, as the filter is used over a period of months, the flow rate may decrease and no longer match that of a new filter.
- On 8 and 12 litre models, two optional Ultimate Star Filter® filters can be fitted. Adding filters does not improve filtration, but it does speed it up.
- If you are going to be away for a long time (more than 3 days), make sure your filters are properly stored. See our instructions for use for explanations on filter storage.