I see lots of posts with pictures on social media from installers proudly showing the magnetite collected on the filter they fitted, each year they show these pictures when the boiler is serviced, the installer feels proud and feels he has done the customer a good service, I would question that.
For magnetite to be present, then corossion is occurring within the system, corossion could be due to any of the following and possibly more
system leak, meaning regular topping up with fresh oxygenated water
incorrect pH for the system materials
Presence of Hydrogen
High electrical conductivity
High flow rates = poor system design
These are just some issues that can cause corossion in a heating system, but all these issues need to be diagnosed and rectified, but it seems now a days the solution is stick a magnetic filter on the boiler and all the problems will go away, well it does not quite work that way, I understand that the boiler is the most expensive part of the system and is why the focus is to protect it, but there is more to the heating system than just the boiler.
In my opinion it is just more dumbing down of our industry, we are dealing with H2O mixing with Cu, Fe, Al, we have gasses present , O2, H, CO2, we also have salts in the water, traces of other metals in the water, I am not trying to over complicate our job, but I am showing the chemical symbols because our industry involves chemistry, we need to approach our job with a slightly more scientific attitude, we don't need a degree in Chemistry, we just need to be aware of the chemical reactions that occur in heating systems and know how to address them, but we have been led down the road that all we need to do is pour in an inhibitor, fit a filter and we need not worry ourselves about anything else.
In my opinion if a heating system is suffering from corossion, the cause needs to be found and that cause needs to be addressed in what ever method best suits the situation, most installers who use chemical inhibitors have no idea of the water makeup, they do not know the pH of the heating water, they do not know the conductivity of the water, they do not know how much free oxygen is present, so how do they come to the conclusion that the system requires inhibitor, a lot don't even know what the inhibitor is supposed to do once in the system, the reason, because they are told that what is needed by the very people who sell the chemicals, of course there will be systems out there that will require chemicals and filters to be fitted, but this should be the exception, not the rule and any chemical dosing should be done by specialist contractors who can measure the correct dosing required, not simply pour in a bottle of whatever came free with the boiler, or was on special offer.
We now have a better choice of materials to work with and we can minimise mixed metal systems, a cause of corossion, my personal approach is MLCP with press joints, this is 100% oxygen barrier unlike other plastics which DO ingress some oxygen although they call themselves a barrier pipe, I now pipe right up to the boiler in MLCP and I only use boilers with 100% stainless steel heat exchangers, the less different materials we have in a system the better.
I think it is very important that new entrants to the industry are not simply taught filters and inhibitors are all you need to know, they need to understand the science behind corossion, why it happens and how it can be addressed without adding components that just mask the problem, standard of installers is dropping in my opinion and things will only get worse if we as an industry do not demand things change, don't get me wrong there are some fantastic installers out there and we see some great work on Social Media, but the good ones are starting to become the minority
The German VDI2035 which is the German standard for heating water as some may be aware, has a statement which says
"If a heating system is constructed with ideal materials and is set up as a closed system according to state of the art knowledge, and if this system is filled with correct water, operated, and maintained properly, then there is no corossion to be expected"
Even the rather basic BS7593:2006 states
"Chemicals should NOT be used as a substitute for correct system design, installation and maintenance"
There will be plenty of people out there who disagree with me and thats fine, but it is important that this matter is discussed and taken more seriously