Magnetic Filter or Chemical Inhibitor
These aren't really alternatives — a magnetic filter traps debris physically and an inhibitor treats the water chemically to slow corrosion — but homeowners often ask which one they need, so here's how each actually works..
These aren't really alternatives — a magnetic filter traps debris physically and an inhibitor treats the water chemically to slow corrosion — but homeowners often ask which one they need, so here's how each actually works.
What the filter does on its own
Captures magnetite and debris circulating in the system before it reaches the boiler's heat exchanger, protecting the most expensive component from wear.
What the inhibitor does on its own
Slows the corrosion process that produces the debris in the first place, but does nothing to remove sludge already present in an unflushed system.
Which wins when
Neither replaces the other. A filter without inhibitor still lets corrosion happen in the water; inhibitor without a filter lets any debris that does form circulate freely. Both together, after a proper flush, is what actually protects a system.
Get your system protection checked
Ask us to check your filter and inhibitor level at your next service — it's a quick check with a real payoff for boiler life.
Questions we get asked
Do I need both if my system is new?
Yes — a magnetic filter and correctly dosed inhibitor should be part of every new boiler installation, not an optional extra.
How often should the filter be cleaned?
It should be checked at each annual service; how much debris it holds tells us a lot about the health of the wider system.
Can inhibitor be topped up without draining the system?
Often yes, through the filter's dosing point if it has one, which avoids a full drain-down for routine maintenance.