In this article, we will focus on the installation of a magnetic separator, i.e. a device that protects the central heating system from contaminants of metallic or post-corrosion origin. It is often simply referred to as a magnetic filter. How should it be installed and what mistakes should be avoided?
Our guide is based on contaminant separators by the Nordic Tec brand – however, most of the recommendations will be very similar and applicable to products from other manufacturers.
A magnetic separator is very effective in cleaning water-based systems (most often central heating systems), operating on the principle of a magnet. Inside the separator there is a magnetic rod (magnetic insert) that generates a strong field attracting fine particles of ferromagnetic contaminants – that is, metallic particles.
When water flows through the separator, all iron filings or metallic parts contained in it, detached fragments of rust, damaged micro-fragments of the system are pulled in by the magnet and deposited on a special filter-sediment trap. In this way, they do not reach the most sensitive elements of the central heating system – such as plate heat exchangers, circulation pumps, underfloor heating manifolds – as well as the most important and most expensive components: modern boilers and heat pumps. Moreover, many manufacturers of heat pumps require magnetic separators to maintain the warranty.
In this way, metallic micro-fragments or scale micro-particles detached due to the action of hard water will also not settle on the walls of the installation – in underfloor heating pipes or in radiators. This will have a definite impact on heating efficiency and energy consumption. The operating principle of magnetic separators is therefore very simple.
Before installation, check that all components that should be included in the set are indeed present. Most people consider this obvious and indeed most ordered sets are complete, but it is worth checking – especially before cutting pipes and shutting down the central heating system. If a gasket or some basic element is missing, we may end up with an inoperative central heating system.
Most separators should include the elements shown in the graphic below:
✅ Often a separate key for operating the air vent and the drain valve is also required. It is not shown in the set overview and not every magnetic filter requires it.
✅ Finally, also check whether threaded elements are equipped with gaskets. This applies to valves as well as O-ring seals connecting individual elements of the magnetic separator chamber. If everything is correct – proceed with installation.
As for where exactly it is best to install a magnetic separator, there are of course different schools of thought, but most practitioners agree that it should be installed on the return pipe, before the device that we want to protect the most. Therefore, it is worth installing it, for example, before a heat pump or before a gas boiler if it is due to having these devices that we decided to install it.
Another school says that the location is not that important, because in a circulating system ferromagnetic particles will eventually be captured anyway if a magnetic filter is present. This is justified only to a certain extent and does not really stand up to real-world conditions.
✅ Absolutely, the magnetic separator must be installed in a place with open access for later servicing.
If we install the magnetic separator at the stage of building the entire central heating system, the matter is simple. However, when installing it in an existing system, we must start by draining the water from it – or at least from the section where the installation will take place (if it can be isolated by valves).
A section of pipe of the required length should be cut out. This length should be specified in the instructions for the specific filter – or, as a last resort, the separator together with the shut-off valves can be measured.
✅ Important – proceed with this step carefully; a common mistake made by amateurs is cutting out too large a gap. It is better if it is too small, as it can be enlarged later, than if it is too large.
After completing this step – install the valves on the outlet and inlet.
The fitting (magnetic filter adapter) should be inserted between the valves and connected in a tight manner.
✅ At this stage, it is important that the direction of water flow matches the direction of the arrow marked on the fitting. Only in this way will the filter operate correctly without placing excessive hydraulic resistance on the system.
Next, using the wrench, tighten the remaining part of the magnetic filter, i.e. the chamber and its cover. Pay attention to the gasket, which is responsible for sealing the thread between the fitting and the rest of the separator. Tighten firmly, but with care.
Once the filter is installed, open the shut-off valves and refill the central heating system with water. Then vent the filter using the air vent.
When the magnetic separator has been vented, check for any signs of leaks, mainly at the connections. Checking for tightness should not be a one-time action – it is recommended to check the tightness again after 6 to 24 hours. Then, even if there are any micro-leaks, you will be able to notice them. You can safely return to this the next day.
✅ A properly installed separator must be in a vertical position, regardless of the position of the pipe on which it is installed.
If there are no leaks, it can be assumed that the magnetic separator has been installed correctly and is operating.
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