Fernox F4 Central Heating Leak Sealer Express 265ml

By Fernox Product code: 14453 Pack size: Each

£12.98 Exc. VAT £10.82

Delivery Address
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Collection Address
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Product Details

Seals small leaks and weeps which may cause pressure loss and boiler breakdown.

Technical Specification
Brand Fernox
Safety Data Sheet click here
Volume (L) 0.265
Delivery details

Covid-19 Update

  • FREE Next Business Day delivery is available for orders over £25 for orders placed before 9pm Mon-Thur and before 6pm Sunday
  • Saturday and Sunday delivery is available for orders placed before 6pm on Friday for Saturday Delivery and 4pm Saturday for Sunday delivery. Items over 30kg can only be delivered next Business Day Mon-Fri. Orders placed after 9pm Thursday will be delivered the following Monday see here for details
  • Pre-12 delivery service is now available for weekday deliveries. Place your order before 9pm Mon-Thur for next business day delivery by 12pm. Orders placed after 9pm Thur and before 6pm Sunday will be delivered by 12pm Monday. UK mainland only
  • Once your order has been dispatched you will receive an invoice email with the courier details and your tracking number
  • Alternatively go to MyAccount, click on your Order History, click on the TRACK icon to link through to the carrier website and the tracking details for your delivery
  • Delivery direct from suppliers is available and specific delivery times will be displayed on the product page
Order Value: Under £25 Over £25 but less than £75 £75 & Over
Next Business Day Mon-Fri (order by 9pm Mon-Thur & Sun by 6pm) delivered before 6pm £5 Free Free
Pre-12 Delivery Mon-Fri (order by 9pm Mon-Thur & Sun by 6pm) delivered before 12pm next day £10 £5 £5
Remote areas standard delivery (2-4 days) £5 Free Free
Saturday Delivery (order by 6pm Friday) delivered before 6pm £10 £5 Free
Sunday Delivery (order by 4pm Saturday) delivered before 6pm £10 £5 Free

Please note items delivered by our suppliers are not available for the options above. Delivery times may vary.

More about Delivery & Returns
Click & Collect details

Covid 19 Update

Click & Collect

We are fully open and delighted to welcome our customers into our branches.

Our opening times are 7am-8pm Monday-Friday, 7am-7pm Saturday and 9-4pm Sunday

Our speedy 5 min Click and Collect service remains one of the safest ways to buy from us and minimises your time in store. Place your order at toolstation.com 7 days a week, and travel to store once your collection confirmation is received by email or text message.

Don’t forget your mobile number – Please ensure that your mobile number is added so that we can text you when your order is ready to collect.

Your items will be held at your selected Toolstation branch for 14 days, after which point your order will be put back to stock and refunded automatically.

Fernox F4 Central Heating Leak Sealer Express 265ml is rated 4.3 out of 5 by 9.
Rated 5 out of 5 by from Discounted price - couldn't go wrong! Fernox additives are excellent value and with this being discounted you couldn't go wrong. Easy to use and put into the system. Great value.
Date published: 2020-06-02
Rated 1 out of 5 by from Fernox F4 Express Although i cant see a leak in system anywhere this did not work for me--pressure still drops,although i will say it was very easy to get into the system.
Date published: 2020-03-02
Rated 5 out of 5 by from Central heating leak stop Easy to use, comes with several Connectors did the job.
Date published: 2020-01-31
Rated 5 out of 5 by from It Works Had a small leak in the central heating system somewhere & the boiler pressure kept dropping. Was unable to find the leak so decided to use Fernox F4 sealer express.Turned off in & out valves on an upstairs rad,removed bleed valve & fired in the Fernox. 2 weeks later & still have no problems.Would recommend.
Date published: 2019-12-28
Rated 3 out of 5 by from leak sealant hard to get into radiator, bought another type
Date published: 2019-12-12
Rated 5 out of 5 by from Absolutely brilliant product and a great price. Following a radiator removal/replacement we had a small pressure drop of about 1 bar over 5/6 days which required regular top up from filling loop. Careful investigation of visible joints, connections and valves etc failed to identify any perceptible leaks and the fear was that maybe an inaccessible joint had possibly loosened below a newly tiled floor, of course there was no way of being sure without pulling the whole floor up! I decided to give Fernox F4 a try as I had nothing to lose. It was very easy to use, adding it to the system via a radiator bleed valve without even having to drain down or depressurise. I am pleased to say that it has been 100% successful and the pressure has now remained stable and constant with no loss over several weeks. As a bonus, we have since found that a small amount of the product residue has hardened just below the nut on one of the rad valves thus indicating where the seepage was occurring so I will be able to carry out a permanent repair in the future if need be, though I may just leave it alone all the time it remains leak free. All in all this is a brilliant product which does exactly what it claims, is very easy to use and was a very good price from Toolstation. Highly recommended.
Date published: 2019-12-02
Rated 5 out of 5 by from Works ! Had a slow leak somewhere in my heating system, losing pressure, used Fernox and everything is now fine !
Date published: 2019-11-02
Rated 5 out of 5 by from Easy to use. Excellent product, Fernox speaks for itself. Like the adaptor, makes it so much easier to use.
Date published: 2019-05-19
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