These frequently asked questions are to provide a better understanding about the topics relating to liquid and water filtration and to answer the questions regularly asked.


What's in my water?

The following contaminants are commonly found in water and can cause the unwanted problems stated. Fileder Filter Systems offer a wide range of solutions to remove these contaminants found in water.

What is in your water depends on the source and delivery system. If your water comes from a private supply (eg. Borehole, lake, river), then a water analysis needs to be undertaken before remedial action is applied. If your water is from mains then your water supplier will be able to provide you with a water analysis.

How to purify water?

Purified water from any source has been treated to remove all chemicals or dissolved contaminants. Filtration is not always a means of purification where by different technologies can be used to achieve different levels of results in terms of water quality.

Commonly used as a reference guide in filtration is The Filtration Spectrum chart. This shows the relative size of contaminants such as particles, elements and ions. Included at the base of the chart is a guide to which sort of filtration to use to remove each contaminant.

Particle filtration = 0.5 ” 1000µm: Includes Bag filtration & Depth filtration to remove sediment, dirt and particulate.
Microfiltration = 0.03 ” 3µm: Surface filtration & Membrane Pleated cartridges cover the majority of applications although elements of Bag filtration, Depth filtration and Hollow Fibre technology cover this common area for filtration requirements.
Ultrafiltration = 0.0025 ” 0.2µm: Includes some Pleated Membrane & all Hollow Fibre cartridges, removes bacteria, fungi and some viruses.
Reverse Osmosis = 0.0001 ” 0.05µm: Reverse Osmosis systems are used to cover the requirements of Nanofiltration & Reverse Osmosis levels of purity, removing aqueous salts for instance.
Deionisation: Although not shown on the Filtration Spectrum, mixed bed Deionising resin attracts and removes the ions left in water and is commonly the last stage in pure water production.


How to change a water filter cartridge?

Changing a filter depends heavily on the type of filter housing that is used. This guide gives typical instructions for filter cartridge removal from a plastic filter housing.

Tools Required

  • Protective / Waterproof gloves
  • Safety glasses
  • Cloths / mop / bucket for any water spillages
  • Suitable receptacle for water drained from the system (if required)
  • Bowl removal spanner
  • O-ring lubricant such as silicone based or petroleum jelly
  • One bucket of soapy warm water
  • One bucket of warm water for rinsing
  • Liquid detergent soap
  • Unscented bleach (5.25% sodium hypochlorite)
  • Replacement filter cartridge(s)

When changing a Water Filter Cartridge remember, it is important to change the water filter cartridge promptly to keep the filter untainted for maximum use. Make sure you have a bucket on hand and something to mop up any spillages that may occur. Ensure the area is clear of any hazards, for example anything electrical.

  1. Close stopcock / shut off water supply to your water filter housing.
  2. Using the relevant removal spanner, remove filter housing sump and drain away the remaining water.
  3. Take out the used cartridge from the filter housing and discard.
  4. Remove the o-ring from the groove in the sump and wide both the groove and o-ring clean. Place the o-ring to one side. *Note: it is common for the o-ring to lift up and remain attached to the head.
  5. Clean and sanitise the filter sump with warm soapy water. Then with diluted bleach, scrub the inside of the sump with a non-abrasive cloth. Rinse thoroughly with clean water.
  6. Inspect the o-ring, which secures between the groove, the bowl and the head, for any damage such as nicks or cuts. Replace with a new o-ring if necessary.
  7. Re-lubricate the o-ring, which secures between the groove, the bowl and the head, with a coating of clean petroleum jelly of silicone grease. Press the o-ring back into the sump groove. *Note: It’s important that the o-ring is seated level in the groove, between the bowl and the head, to ensure a proper filter seal.
  8. CG end cap filter – Remove the new cartridge from its packaging and place it into the sump. Ensure the o-ring seal on the filter cartridge is correctly fitted around the spigot in the housing head.
  9. Screw the sump of the filter housing back on the head by hand. Do not use the sump removal spanner as this may lead to over tightening and damage.
  10. Repeat steps for each cartridge that needs to be installed. Ensure the correct cartridge is in the correct housing. *Note: The larger micron rating should sit upstream of lower micron ratings. Check the direction of flow on the filter housing head if you are unsure.
  11. Turn the water supply back on, allow system to fill. Check for leaks. If leaks are detected please repeat process.
  12. Flush the cartridge thoroughly. After following this guide your system should be ready for use.

Reverse Osmosis

How does Reverse Osmosis (RO) work?

RO systems work by using a pump to push inlet water across a semi-permeable membrane. By applying a back pressure, the water molecules pass through the membrane leaving almost all (95% to 99%) of dissolved salts on the concentrate™ side of the membrane. The water that is directed through the semi-permeable membrane has the majority of dissolved salts removed from it and is known as permeate™.

The salt concentrated water (known as concentrate™) is sent to drain and this action across the membrane washes contaminants from the surface preventing the membrane from fouling. Some systems allow for a proportion of the concentrate to be recycled through the RO feed to save water albeit at the detriment to membrane life. All membrane manufacturers agree that the life of the membrane is largely affected by the pre-filtration and pre-treatment used, effective pre-filtration and pre-treatment where required is the key to efficient use of membranes. The temperature of the feed water should also be considered as this affects the level of permeate production.


How does Carbon work and what does it remove?

Carbon is heated to 540°C in the absence of oxygen which bakes off any impurities and then is superheated to 870°C using steam to activate the carbon. This process creates a network of cracks and pores which results in a massive surface area, maximising the effectiveness of the carbon.

Activated carbon treats contaminants that effect the taste and odour of water, including chlorine, herbicides and other chemicals. The contaminants in the water come into contact with the activated carbon and are adsorbed by chemically binding, resulting in the quality of water improving. Below is a list of common chemicals that activated carbon is able to remove from water sources. Activated carbon can also designed to include limescale control with the addition of phosphate.


What is a Pleated filter?

A pleated filter utilises a single sheet of filter media, this type of filtration is also known as surface filtration. The sheet of media is tightly pleated to increase the surface area of the physical barrier compared to a flat sheet. Surface filtration works by incoming particulate of a certain micron size being blocked by the filter media.

The blocked particles form a cake on the surface of the filter media, the caking effect increases the efficiency of filter. There are several different types of media that can be pleated which are suitable for different filtration requirements, please contact Fileder for our expert advice on which media best suits.


What is a spun filter?

Spun filters are named because of the manufacturing process where a spinning mandrel (metal bar) has polypropylene fired at it through jets. This creates a tightly packed fibrous matrix which is wider spaced on the outside of the filter than the inside, this is known as graded density. The graded density allows for depth filtration.

Depth filtration as the name suggests is the process of filtering through a depth of media, of which there are two different particle retention methods. Mechanical retention is where particulate is physically caught by the fibrous media preventing them from continuing downstream. Adsorptive retention is where particles are attracted to the media via an electrostatic force called Van der Waals. The positively charged polypropylene media attached negatively charged particulate.


What is Bag Filtration?

Bag filters (also known as sock filters) are designed for use in high flow rate applications or for use with gelatinous liquids. A system of a stainless-steel housing (or for smaller flows, a polypropylene housing) and a bag filter will trap a large amount of particulate making bag filtration an economic choice for bulk solids removal. They are simple and quick to change, minimise process downtime, limit operator exposure to the process liquid whilst reducing maintenance downtime and expense.

Ranges offered include, micron ratings from 0.5 to 1000µm, various media types (for applications involving aggressive liquids or where washing and re-using the bag is preferred), various grades of efficiency and extended life.


How do I remove Cryptosporidium from water?

This worm-like parasite, encased in a shell, is called Cryptosporidium (or Crypto™ for short). Its a very small (3-6µm) and very nasty waterborne contaminant that can be hard to detect, yet poses a significant health risk. It often prompts water authorities to send out boil water notices.

It is commonly found in water supplies that have been contaminated with cattle manure. Drinking this tiny monster could give you a disease called Cryptosporidiosis, an infection of the bowels which can lead to diarrhoea and vomiting. Physical filtration is the best way to remove Crypto from water using absolute rated cartridges. UV can be used to dissociate the cells of the parasite but the exposure levels need to be incredibly high for effectiveness that Surface filtration is more commonly used to effectively remove the parasite from the feed flow.

How do I remove Legionella from water?

Legionella is a waterborne bacteria which, if inhaled via a mist (such as shower or tap spray), can cause Legionnaire’s disease, a potentially fatal form of pneumonia. Unlike most microorganisms found in untreated water, Legionella bacteria are found to attack the respiratory tract which can worsen if the infected person is suffering from chronic lung disease or other high-risk illnesses.

Physical removal of bacteria at the point-of-entry (POE) to a building or at the point-of-use (POU) in an application is the only method that removes legionella from the water. These bacteria flourish in warm waters therefore typically a certified 0.2µm absolute rated filter will retain bacteria, fungi and particulate and protects from risk of waterborne infection.

Absolute Cartridges

What is an 'absolute rated' cartridge?

The term absolute is used in filtration to describe the removal efficiency of a filter cartridge.

If a cartridge is stated to be absolute at a specific micron size, it means that the filter will remove at least 99.98% of the particles, from the feed solution, at the stated micron size or above.

Beta ratios are commonly used to show the absolute rating of filter. Beta ratio testing involves adding specified contaminate of known sizes to a fluid being pumped through a filter. The particles are counted upstream and downstream to determine an efficiency called the Beta Ratio. For example: 10,000 particles counted in the feed stream 2 particles counted downstream of the filter.

Filters with a higher beta ratio retain more particles at their stated micron rating and therefore have a higher efficiency. The table below shows common Beta ratios and their corresponding filter removal efficiency.

Due to their high removal efficiencies at specific micron sizes, absolute filters are commonly used in critical applications such as, hospitals and breweries whereby the control and/or removal of microorganisms is fundamental.

Filter Housings

How to select the correct filter housing?

The wide range of filter housings and filters Fileder stock and supply offers a wide choice to select from. Choosing the most suitable housing for your application and specifications is important to achieve the result desired.

To determine which filter housing will suitable for your application you would ideally know the following:

  • Liquid type – aggressive chemical, water…
  • Maximum flow rate
  • Maximum pressure
  • Operating and peak temperatures
  • Location – indoors, outside…
  • Filter type – cartridge, bag…
  • Cleaning regime
  • Pipework size
  • Budget
  • Quality assurance requirements
  • Maintenance and filter change timing – duty / standby, parallel housings, side-stream filtration…

With this information, it is easier to choose which housing is required. The selection guide below will help you determine the most appropriate cartridge filter housing for the application, note that each housing has port size options and for information regarding the bag filter housings options or further clarification, please contact Fileder and we’ll be happy to assist.