Fernox F4 Central Heating Leak Sealer Express 400ml

By Fernox Product code: 83815 Pack size: Each

£20.98 Exc. VAT £17.48

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.

Suitable to be used throughout a central heating system to seal small leaks and weeps which may cause pressure loss and boiler breakdown. Once dispersed within the system it will be effective 1-24 hours after application. The unique sealing efficiency of this proven product has been specifically developed to prevent blockages or restrictions within the boiler or vulnerable system components such as pumps and safety devices.

• Seeks out and seals inaccessible, internal microscopic leaks fast
• Quick and convenient – doses in 30 seconds - no need to drain down the system
• Non-toxic, environmentally friendly formulation, compressed air propellant and 100% recyclable can
• One 400m canister treats up to 130 litres of system water (16 radiators) and the equivalent of 250m2 of underfloor systems.

Technical Specification
Brand Fernox
Manufacturer ID 62422
Volume (L) 0.4
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 400ml is rated 4.6 out of 5 by 31.
Rated 5 out of 5 by from Does what it says in the label Worked a treat, weeping radiator valve fixed with this stuff, thank you Fernox
Date published: 2021-04-13
Rated 5 out of 5 by from Stops leaks fast Great product, easy to use, came with all the attachments needed, stopped the small leak I couldn’t find. Saved a lot of time lifting the floor/ cost of finding the fault. I highly recommend before more drastic action, and for the cost, it’s hard to beat.
Date published: 2021-04-05
Rated 4 out of 5 by from Good product but may need 2 cans for bigger house Nice product easy to use. Cannot say for certain it has worked but the boiler is now losing pressure less than before. I have some long pipe runs so Might need another can of Fernox to do the trick.
Date published: 2021-03-29
Rated 2 out of 5 by from Not brilliant Cap supplied too big so had to change to male connector and then even after a minute there was a fair bit left in the can. Will give it a ferw days and if not fixed I'll have to use the filter. Any suggestions pls?
Date published: 2021-03-12
Rated 5 out of 5 by from Worth a try before costly repairs. Quick and mess free. Need two cans for a ten radiator system rather than the one as stated but that’s still way cheaper than pulling up floorboards to find a weepy joint. Worth a go if your boiler is losing pressure.
Date published: 2021-03-06
Rated 5 out of 5 by from It really does work! Our central heating (combi boiler) was losing pressure and needing topping every couple of days. I looked everywhere and couldn't find any obvious leaks, so I thought I'd give this a go. It's now been two weeks and I haven't had to top it up! I used the filling loop on the boiler and the whole job took less than five minutes. This is one of the few products that actually does deserve it's five star reviews.
Date published: 2021-02-13
Rated 5 out of 5 by from Would recomen this product. Had a pinhole leak in one radiator, I was unable to replace the rad without taking up a newly fitted floor. It says you don't need to release the pressure, but I used the pressure release at the boiler. Anyway this product sorted my problem and I'm very happy I didn't need to lift the floor.
Date published: 2021-02-12
Rated 5 out of 5 by from Appears to have done the trick! Appears to have done the trick!
Date published: 2021-02-09
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