Inhibitor and Heating System Water Treatment
Inhibitor is a chemical added to sealed heating systems to slow corrosion and limescale formation inside pipework and radiators.
Inhibitor is a chemical added to sealed heating systems to slow corrosion and limescale formation inside pipework and radiators. It's cheap, easy to top up, and one of the most neglected pieces of routine maintenance on an otherwise well-cared-for system.
What it does
It coats internal metal surfaces to reduce the electrochemical corrosion that produces black sludge, and helps limit scale formation in hard water areas.
How it fails
Concentration drops over years, gets diluted whenever the system is topped up with fresh mains water, or is simply never added after a flush or repair.
Repair or replace
There's nothing to repair — inhibitor is tested and topped up, or the system is fully drained, flushed and freshly dosed if levels have been low for a long time.
Check your system's inhibitor level
Tell us when your system was last flushed or dosed and we'll test the concentration at your next service.
Questions we get asked
Can I add inhibitor myself?
It's straightforward to add via a radiator or filling loop if you're comfortable doing so, though testing the correct concentration is best left to a service visit.
Does inhibitor stop a leak?
No, inhibitor protects against corrosion; it doesn't seal existing leaks, and we wouldn't use it as a substitute for finding and fixing one.
How do you test inhibitor levels?
With a simple dip-test kit during a service that reads the concentration remaining in the system water.