String filters – cartridges for effective mechanical water filtration

String filters are proven cartridges for mechanical water filtration, used wherever solid contaminants need to be effectively stopped before further treatment. Their task is to capture deposits such as sand, rust, silt, and other particles suspended in water, which translates into better protection for the installation, fittings, and subsequent filtration stages.

In this category, you will find string cartridges made of polypropylene nonwoven material wound onto a filter core. These solutions are designed for the mechanical removal of contaminants from water and are available in various micron ratings and sizes. The most popular variants include 5, 10, and 20 microns, and a commonly chosen standard is 10-inch string filters, which fit most standard корпус filter housings.

What are string filters?

String filters, also called string cartridges, are filtration elements made of polypropylene nonwoven material wound onto a filter core. This design creates a layered structure resembling string, thanks to which the cartridge effectively traps mechanical impurities present in water.

This solution is widely chosen for both household and industrial applications. String cartridges are available in various sizes and filtration accuracy classes, so they can be matched to individual user needs and to most filtration systems.

How does a string cartridge work?

A string cartridge works on the principle of mechanically trapping contaminants. During water flow, solid particles settle on the fibers of the polypropylene string. The layered winding of the material provides a large filtration surface area, which affects both efficiency and cartridge lifespan.

In practice, this means that a string filter can serve as a very good preliminary stage, preparing water for further, more precise filtration.

Key benefits of using string filters

• effective removal of mechanical impurities such as sand, rust, silt, and suspended matter,
• protection of the water system, fittings, and devices against deposits,
• extended lifespan of subsequent filtration stages,
• the ability to match the micron rating to water quality and the expected effect,
• availability of popular sizes fitting standard housings,
• use in both home applications and selected industrial installations.

Types of string cartridges by micron rating

The basic difference between string cartridges is the micron rating, meaning the size of particles the filter can retain. Choosing the right filtration accuracy affects both cleaning efficiency and water flow.

5-micron string filter

This is a good choice when water contains fine impurities such as silt or grains of sand. It provides high filtration accuracy, but it may affect water flow reduction more than cartridges with a higher micron rating.

10-micron string filter

The 10-micron variant is often chosen as a universal solution. It traps larger particles such as rust and coarser impurities, while usually maintaining a favorable balance between filtration efficiency and flow performance.

20-micron string filter

20-micron cartridges are primarily suitable for preliminary filtration. Their task is to capture larger particles before subsequent, more precise stages of water treatment. An advantage of this solution is also higher flow capacity.

How to choose the right string cartridge for a water filter?

Choosing the right model depends primarily on water quality and the specifics of the installation. Before purchasing, it is worth paying attention to a few basic issues.

• Type of contaminants – for fine deposits such as silt or fine sand, 5 microns may be worth considering; for larger impurities, 20 microns may be a good choice.
• Required filtration level – the lower the micron rating, the more precise the filtration.
• System specification – make sure the cartridge fits the filter housing being used.
• Water flow – more precise cartridges may restrict flow more, so they should be selected according to the actual needs of the installation.

Tip: the most popular are 10-inch string filters, which fit most standard filter housings. This is a common choice for home water filtration systems.

String filter or foam filter?

The choice between a string cartridge and a foam cartridge depends on the type of contaminants and the expected filtration effect.

• String filter retains larger particles such as sand, silt, and rust better. It is more resistant to clogging and usually has a longer lifespan.
• Foam filter performs better with finer impurities such as mineral sediment, but it may require more frequent replacement.

If the main problem is typical mechanical impurities present in the water system, a string cartridge very often proves to be a practical and economical solution.

String filters as pre-filter cartridges

String cartridges are often used as pre-filters. Their task is to stop larger contaminants before further, more precise filtration. Thanks to this, they help protect subsequent cartridges and extend their lifespan.

This is particularly important in multi-stage systems, where the first stage is meant to take on the greatest load associated with the presence of deposits and suspended matter.

10-inch string filter, PP20 and PP10

10-inch string filter

10-inch string filters are a standard size fitting most popular filtration systems. They are versatile, readily available, and offered in a wide range of micron ratings, which is why they can be used both at home and in many utility applications.

PP20 and PP10 string filter

Models referred to as PP20 and PP10 differ primarily in the degree of filtration accuracy resulting from the density of the polypropylene string winding.

• PP20 – retains larger particles, is well suited for preliminary water cleaning, and usually provides higher flow capacity.
• PP10 – is responsible for more precise filtration, removes finer impurities better, but may restrict flow more.

How often should a string filter be replaced?

Replacement frequency depends on water quality, the degree of contamination, and the amount of filtered water. It is generally assumed that string filters should be replaced every 3 to 6 months to maintain optimal performance.

• regularly check the level of cartridge contamination, preferably once a month,
• pay attention to pressure drop or reduced water flow,
• if you notice a change in the taste or smell of the water, it is also worth checking the condition of the filtration.

Bacterial growth and a string cartridge

Cartridges made of polypropylene do not have antibacterial properties. For this reason, regular inspection and timely filter replacement are very important to maintain the effectiveness of the entire system. In installations where microbiological safety is also important, it is worth remembering that mechanical filtration and protection against bacteria are two different issues.

Why choose string cartridges from this category?

In this category, you will find water string filters designed for installation in standard filter housings. These are solutions valued for simple installation, a wide selection of variants, and a favorable price-to-quality ratio. Among popular products, users also often point to UST M string cartridges.

A properly selected string cartridge helps improve the quality of mechanical filtration, protects the installation, and supports the proper operation of the entire water treatment system.

FAQ – frequently asked questions about string filters