A magnetite filter is a filter with a strong magnet. The purpose of the magnetite filter is to filter out mainly iron oxide and magnetism but also other magnetic impurities in the heating system. Magnetite and iron oxide are formed in heating systems that are waterborne and this happens when the oxygen in the water reacts with metal in the heat pump or in the radiator system. The magnetite and impurities negatively affect the heating system by impairing its function and destroying the system from the inside. A common error is that the circulation pump breaks and needs to be replaced, which can cost from SEK 3 to 15,000 depending on the model and size.

Different brands of magnetite filters

There are many different brands that manufacture magnetite filters. The most common are Boilermag, Adey (largest in Europe), Flamco, Ahlsell and Nordicold (see picture below).

Differences between magnetite filters

What usually differentiates between different brands of magnetite filters is

• The material they are made of, either metal or plastic.
• If they have a regular filter to collect larger non-magnetic particles.
• Whether the magnet sits directly in the filter container or not. If it sits in the water, the magnetite sticks directly to it, which makes cleaning a little more awkward and dirty.
• Whether it can be mounted on vertical or horizontal pipes.
• If it has wifi and can notify when it needs cleaning.
• The strength of the magnet.

Magnetite filter, before and after

The picture below shows what a magnetite filter can look like after it has attracted magnetite in a heating system. The left picture is with magnetite and the other is after cleaning. It is also clear how the magnetic fields move.

This is how magnetite occurs in the water

Magnetite occurs when the oxygen in the water in the radiator system and the heat pump reacts with iron and metal. Most of the time, the water is "dead" in the radiator circuit, which means that it does not contain any air, but when you have filled up, new oxygen-rich water enters the radiator circuit and then the magnetite can increase.

Water quality affects heat pump wear

There are various things in the water that affect the magnetite and how much the water wears on the heat pump and its parts. Below are a couple of examples of things that affect how much the water wears on the heating system and radiator system.

Alkalinity - low alkalinity is bad and causes the water to attack metal to a greater degree.

pH value - if it is low, the water is acidic and wears more on the pipes and, in the worst case, leaks occur.

Aggressive carbonic acid - occurs when carbon dioxide is neutralized. This is negatively charged and then attacks what is positively charged, for example copper.

Conductivity - if your water has a high conductivity, it has a great ability to conduct electricity, which accelerates corrosion. 

 

The picture above shows the amount of magnetite in a circulation pump. The brown is magnetite and due to the amount the circulation pump has cut after the flow has gotten worse and worse over time.  

Magnetite filter in the bargain?

After reading all the negatives that magnetite filters can cause, it would be good if the magnetite filter came with or was installed in a new heat pump.