62454 265ml Super Concentrated F1 Protector - 100 litres Treats

Fernox is, of course, known for being oi oi oi very effective at preventing corrosion in your central heating system and the concentrated version is the best choice for filling into magnetic filters when you service them as the filter cups on the smaller filters don't hold much liquid. Because it's concentrated you can get more into the system in one hit.

Good price and service.

Works well

Good product

This is an essential protector to add to radiator systems to prevent rust and protect. Being concentrated, it's easy to add to the system. I'm using a dosing tool to do so. Add it in and it'll circulate and mix in the system fairly quickly. This is good value for a concentrate and easy to use. I also like the smell of it. The function of it is really good and we've been using it for years. It does also help quieten the system a little, from my experience and keeps ethi gs working as they should. Definitely recommended.

Treats the same size system, just a more concentrated form of the full-size product (I tend to buy whichever version is cheaper each year). Smaller amount to be added to the system means having to take less water out of the system to make room. You might even get away with not removing any if your system needs a lot of air bleeding out of it and you add this first (though I've never actually tried that, my system gets very little air in it).. As for effectiveness, I started with a clean system and the water has stayed clear for years with no hint of the black sludge that many systems have. This won't fix an already sludge-filled system - clean it first (or have it done for you), then top up with this every year and that should be the last clean your system needs for a very long time.

Always used Fernox, never a problem. Very good price, but near the end of its printed shelf life. Shouldn't be a problem though, as it is sealed and would be in the system for years anyway.

I use Fernox inhibitor every 18 to 24 months for filling my heating system after a thorough clean. The last two runs were pretty much redundant, as the water was almost colourless, with very little sludge. Unless anything happens, I'll probably keep doing the same thing in the future -- it's better to do a bit extra work every hear or two rather than spending much more time (and money) on trying to clean the blockage.