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Fernox F1 Central Heating Inhibitor & Protector Express 400ml

4.7 (166 reviews)
SKU: 260223155522009 EAN: 5014551582293

Compare 1 price for Fernox F1 Central Heating Inhibitor & Protector Express 400ml — from £24.99 across 1 UK seller including Toolstation.

£24.99 6h ago
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Customer Reviews 166

4.7
166 reviews
5 star
139
4 star
18
3 star
3
2 star
0
1 star
6
Great inhibitor
5.0
February 21, 2026
Madjonno Verified Purchase

One of the best inhibitors for easy dosing ! Also quality product

Good product
5.0
January 26, 2026
Camel 1 Verified Purchase

Good product to spray it in to a radiator was very easy and quick

Works perfectly
5.0
December 6, 2025
Nick 876 Verified Purchase

Very easy to add inhibitor via the Spirotech magnetic filter. After flushing the filter, just screw on and squirt. Couldn’t be simpler.

Good leak sealer
5.0
December 1, 2025
Mahony Verified Purchase

I was suffering from an unknown leak as there was no sign of any stains around the house. I injected this through a bleeder valve in a radiator and then ran the whole isystem with all radiators on fully. So far ,3 weeks ago. the system is working correctly. How well the inhibitor is working Ido not know as there is no way of measuring this. So from my point of view, the only way you know it works is if you have a leak, and it seals it. The manufactures say they give you a 12 month guarantee. How cpudyhey possible do this as you have no means of recording, in their system, that you have injected it in your system. How then do you measure how the inhibitor is working?

Quality product
4.0
November 26, 2025
Badman Verified Purchase

Express version is very easy to put into the central heating system via towel radiator or the filling loop

Good Inhibitor - Poor Instructions
4.0
November 12, 2025
PeterPic Verified Purchase

Easy to inject via a radiator once you discover how the trigger and bits fit together. Unfortunately the instructions don't actually mention you have to cut the flexible tube so it was difficult understand how it all joined up. Had to find alternative instruction via the internet - even Fernox website not clear.

Easy to use, but more expensive than plain bottle, so paying for convenience / speed
5.0
November 5, 2025
34cfbc91-e0a7-5905-a411-2c728fd54a64 Verified Purchase

Easy to use using filter connection. My system was pressurised to about 1/2 bar when used, and it pumped in about 440g of inhibitor. (Weight recorded before and after)

No lable
4.0
September 1, 2025
06f7b6a8-e42e-5b0a-b349-b8589da7967c Verified Purchase

Does exactly what it says on the can. Bit disappointed that there was no self adhesive label to stick on expansion tank to advise date product was applied. Had to make my own.

Trusted Reliable Inhibitor
5.0
July 24, 2025
Bruggen Verified Purchase

Fernox is a name that I know and trust. I have used their products over the years and in conjunction with their TF1 filter I have had no problems with dirt or magnetite building up in my system. The express version is easy to use, I have used it both into my filter and into the top of a new radiator using the included adaptors.

Fernox F1 a breeze to add
5.0
July 23, 2025
WINCO63 Verified Purchase

Made adding inhibitor a breeze it added via filling loop.

F1
5.0
May 27, 2025
JO40 Verified Purchase

This product is great. I always use it when doing maintenance on my ThermalStore Heating system. It keeps the the System very Happy!

Easy to use
5.0
May 22, 2025
J Harris Verified Purchase

Easy to dose into a radiator, worth the extra money to make it easy

Used for top up
5.0
May 5, 2025
CDrake Verified Purchase

The spout on the top is a little awkward, with a quick look at the online video it was easy to use though. Hard to say if it’s doing what it should be but we followed our instructions so hopefully it’s running around doing its job!

Didn’t work for me!!
1.0
April 15, 2025
Simon Butcher Verified Purchase

Im not a plumber but class myself as a very competent DIYer however i tried the various adapters in the kit in an attempt to top up my heating system. Followed the instructions carefully but both times the pipes blew off covering me and the surrounding area in Fernox! I ended up dropping water out of the system and topping up through an upstairs towel rad with the normal Fernox.

A DIY revelation
5.0
April 13, 2025
DIY NickF Verified Purchase

I bought this when the price was reduced, so it was the cheapest option. Using it was a revelation; very simple and easy to use into the radiator bleed valve port. I shan't be going back to the old style pour-it-into-a-funnel method.

Good product, limited instructions
3.0
April 11, 2025
Whattiols Verified Purchase

Product itself good but instructions left a bit to be desired

Easy way to dose with Fernox.
5.0
February 24, 2025
GreyOnTop Verified Purchase

I applied via Sigma magnetic filter with no problems, following instructions on the tin which included flushing the filter first. I was a bit intrigued by the trigger as I could not see how it worked but it did.

Using Fernox F1
5.0
February 21, 2025
Mo again Verified Purchase

Easy to connect via the TF1 Filter and takes 30 seconds. Result using fernox Express Inhibitor Test strips showing change from 0ppm to optimum 150ppm protection.

Inhibitor top up
5.0
February 15, 2025
Steve A c Verified Purchase

Picked this up from local store to top up heating system following some recent work involving a part drain down. Product was very easily inputed through Fernox filter just recently fitted which made it simple to use and all done in literally 5 minutes. Will use again for top ups, highly recommended.

All good 👍🏼
5.0
February 6, 2025
S_m Verified Purchase

Easy to use with the Fernox magnetic filter, followed the Fernox guidance video and went smoothly

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