When should the cartridges of a water filter be replaced?

This is a question we receive frequently. We have also come across people who have not replaced their cartridges in over 3-4 years, yet continued to drink water from the filter. Periodically replacing the cartridges is very important in order to always have clean and healthy water.

Filter cartridges are practically the most important part of a water filter. Depending on the model of filter you have, these cartridges need to be replaced more or less frequently. The most important factors are water quality and the size of the filter cartridges.

Each manufacturer recommends replacing the cartridges after a certain volume of filtered water or after a set period of time, whichever comes first.

The information in this article applies universally to most filtration systems. On average, the maximum filtration capacity of cartridges is 4000 litres, with a lifespan of 6–9 months. This quantity and lifespan are calculated by manufacturers for situations where the incoming water is of average quality. If water quality is very poor, these figures decrease considerably.

In most cases, a family of 3-4 people does not consume 4000 litres of water within the cartridge lifespan. In this case, you do not need to worry about how much water you have consumed — simply remember when you last replaced the cartridges and track the time elapsed since then.

Depending on water quality, sometimes only certain cartridges need to be replaced more quickly. The most common water-related issues are as follows:

1. Sand, rust, sediment, etc.
If your water is visibly dirty, you need to replace the first cartridge of the system more often (every 3-6 months). This cartridge is the most exposed and collects debris quickly. If you have a transparent housing, you will be able to see the level of contamination and the colour of the cartridge. When it has turned dark brown, it needs to be replaced. However, keep in mind that most cartridges filter from the outside inward. This means that if the outside is only slightly dirty, the inside may still be fine and the cartridge can be kept a little longer.

2. Very high hardness
If you notice white marks on sanitary fixtures, glasses or dishes, it means you have a high concentration of calcium and magnesium (hard water). This means you need to replace the softening cartridge every 3-6 months.

3. Excess chlorine
If unfiltered water has a whitish appearance and contains a lot of chlorine, all cartridges containing activated carbon need to be replaced more frequently. Activated carbon is an excellent absorbent, but it has a maximum absorption capacity and must be replaced every 3-6 months.

4. Strange taste or odour
If the water has a strange taste or odour before filtration, all cartridges must be replaced as soon as this taste or odour appears in the filtered water as well. This indicates that the cartridges no longer have absorption capacity.

5. Bacteria in the water
Although bacteria should not be present in tap water, they sometimes exist due to very old pipe networks. Your filter must include a special cartridge for bacteria. This cartridge should be replaced as soon as green formations (such as slime) are observed inside it. Bacteria in water can be eliminated using an ultrafiltration cartridge, reverse osmosis, or UV lamp sterilisation.

Regardless of your water type, to always have good-quality water, I recommend checking the condition of your cartridges every 2-3 months. In practice, this means opening the first housing and inspecting the cartridge. Additionally, the best sign that cartridges need replacing is a changed taste or odour in the filtered water. If it has become noticeable and unpleasant, I recommend replacing at least the pre-filters (usually 1, 2, 3).

We recommend that everyone purchase only filtration systems that use standard-size cartridges. This way, the cost of consumables is much lower.

On FILTRO.ro you will find complete filter sets ranging from 45 lei to 300 lei. Check here for the list of replacement cartridges.

Frequently Asked Questions

Why is it important to replace filter cartridges on time?
Periodically replacing the cartridges is essential to maintain clean and healthy water. Cartridges are the main component of the filtration system, and if they are not replaced on time, filtration efficiency drops and you may end up consuming inadequately treated water.

How often should water filter cartridges generally be replaced?
Manufacturers recommend replacing cartridges either after a certain volume of filtered water or after a set period of time, whichever condition occurs first. On average, the maximum capacity is approximately 4000 litres, with a lifespan of 6–9 months for average-quality water.

What factors affect the lifespan of cartridges?
Lifespan depends mainly on the quality of the incoming water and the size of the cartridges. If the water is heavily loaded with impurities, the filtration capacity and usage period are significantly reduced.

Should I track the volume of water consumed or just the time elapsed?
In most cases, a family of 3–4 people does not consume 4000 litres in 6–9 months. Therefore, it is sufficient to track the time elapsed since the last replacement and follow the recommended interval.

If the water contains sand, rust or other visible impurities, what should I do?
In this case, the first cartridge (sediment pre-filter) needs to be replaced more frequently, typically every 3–6 months. If you have a transparent housing, you can monitor the level of contamination. When the cartridge turns dark brown, it is time to replace it.

What should I do if my water is very hard?
If white marks appear on sanitary fixtures or glasses, the water has a high hardness level. In this case, the softening cartridge may need to be replaced every 3–6 months, depending on the level of calcium and magnesium in the water.

What happens if the water contains a lot of chlorine?
If unfiltered water contains a lot of chlorine, activated carbon cartridges will be consumed more quickly. Activated carbon has a limited absorption capacity, and under these conditions replacement every 3–6 months may be necessary.

How do I know when filters are exhausted based on taste or odour?
If the filtered water starts to have an unpleasant taste or odour, it is a sign that the cartridges have lost their absorption capacity. In this case, replacing them is recommended — at least the pre-filters.

Does the filter remove bacteria?
Not all filters remove bacteria. For this purpose, a special cartridge for microorganisms is required, or technologies such as ultrafiltration, reverse osmosis or UV lamp sterilisation. The antibacterial cartridge should be replaced when visible formations appear or according to the manufacturer's recommendation.

How often should I check the condition of the cartridges?
It is recommended to check the condition of the cartridges every 2–3 months. A simple method is to inspect the first cartridge. Additionally, any noticeable change in the taste or odour of the filtered water indicates the need for replacement.