What is a bag filter?

A bag filter is a filtration system that uses a replaceable filter bag inside a pressure housing to remove suspended solids and particulate contamination from water and other compatible liquids. They are widely used for commercial, industrial and process water filtration.

How does a bag filter work?

Water enters the bag filter housing and passes through the filter bag. Particles larger than the bag’s micron rating are retained within or on the filter media, while the filtered water exits the housing.

What micron bag filter do I need?

The correct micron rating depends on the particles you need to remove and the requirements of downstream equipment. Bag filters are available in a wide range of micron ratings, from coarse filtration to very fine particulate removal. For heavily contaminated water, staged filtration using progressively finer micron ratings can help extend filter life.

What does the micron rating of a filter bag mean?

The micron rating indicates the approximate size of particles the filter is designed to capture. One micron (µm) is 0.001 mm. For example, a 5-micron filter bag provides finer filtration than a 25-micron bag.

What are filter bags made from?

Common filter bag materials include polypropylene, polyester and nylon. Different materials offer different temperature and chemical-resistance characteristics, so the bag should be selected according to the liquid and operating conditions.

What is the difference between Size 1 and Size 2 filter bags?

Size 1 and Size 2 are common industry-standard bag dimensions. Size 1 bags are approximately 7” diameter × 16” long, while Size 2 bags are approximately 7” diameter × 32” long. Size 2 provides a larger filtration area and is generally better suited to higher flow rates or applications requiring greater dirt-holding capacity.

How often should a water filter bag be replaced?

There is no fixed replacement interval. Filter life depends on water quality, solids loading, flow rate, micron rating and filtration area. Monitoring the pressure differential across the bag filter housing is one of the best ways to determine when a bag requires replacement.

What does an increase in pressure across a bag filter mean?

As the filter bag captures contaminants, resistance to flow increases. A rising differential pressure between the inlet and outlet generally indicates that the bag is becoming loaded and may require replacement.

Can bag filters be used for borehole water?

Yes. Bag filters are commonly used to remove suspended sediment, sand, silt and other particulate matter from borehole and well water. However, dissolved contaminants such as iron, manganese or hardness normally require additional treatment rather than mechanical bag filtration alone.

Can a bag filter remove bacteria from water?

Standard bag filters should not be relied upon as a method of water disinfection. Where microbiological contamination is a concern, an appropriately designed treatment system such as fine pre-filtration followed by UV disinfection may be required.

Can bag filters remove iron from water?

A bag filter can capture particulate or oxidised iron but will not normally remove dissolved ferrous iron. Dissolved iron generally needs to be oxidised or treated using a suitable specialist filtration process before it can be mechanically filtered.

Are bag filters suitable for high flow rates?

Yes. One of the main advantages of bag filtration is the ability to handle relatively high flow rates while providing a large dirt-holding capacity. The achievable flow depends on the housing size, bag type, micron rating, water quality and acceptable pressure drop.

What is the difference between a bag filter and a cartridge filter?

Bag filters generally offer high flow capacity and excellent solids-holding capability, making them particularly useful for applications with significant particulate loading. Cartridge filters can provide finer filtration and are available with a much wider range of specialist media. The best choice depends on the required flow rate and contaminant.

Can I use a finer micron bag to improve filtration?

Yes, but selecting an unnecessarily fine bag can increase pressure drop and shorten filter life. Where the incoming water contains a large amount of sediment, using a coarse bag followed by finer filtration is often more efficient.

Are filter bags washable and reusable?

Some filter bags can be cleaned and reused depending on their construction and application. However, disposable bags are normally replaced once loaded, particularly where maintaining consistent filtration performance is important.