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Fernox F4 Express Leak Sealer 265ml (61837)

Internal leak sealer, stops small leaks. Treats up to 10 radiators. Quick and convenient, doses in only 30 seconds. Ideal for reducing pressure loss from sealed systems. Seeks out and seals most weeps and leaks.

  • Treats up to 10 Radiators

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£25.99INC VAT (£98.08/Ltr)

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Rated 4.7 out of 5 by 3 reviewers.
  • 2016-08-27 T10:34:12.666-05:00
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Rated 4 out of 5 by Weeping Joints My central heating had developed a number of annoying leaks over the summer, that didn't want to seal up. If you've got assistance injecting into an ordinary radiator might be possible but I found you need too many hands as injector doesn't stay in under pressure! I injected into a towel rail radiator that let me use the large screw in adaptor. This worked great with just two hands, useful when alone :) Had some green leaks first night but seems to have the job perfectly. If you know where leaks are put something underneath to catch anything as the green is a bit messy. It found one I didn't know I had which resulted in a pool of green on the tiles, it cleaned up OK but carpet might not so beware!! 1 Oct 2015
Rated 5 out of 5 by Easy to use The product was very easy to use, connected straight on to the filling loop. Just hope it does what it is supposed to now it's in the water 14 Jan 2015
Rated 5 out of 5 by Leak fix Used 2 cans of this as we have well over 20 rads on our system to fix a internal leak in our oil fired boiler and it worked perfect.. Within two days there was no leak at all and the leak was more than a tiny one. With it been winter we did not want to be without a boiler so thought this product was great and easy to inject into the system. 14 Jan 2015
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1 Question  1 Answer

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We have 11 radiators, but some of those are large, so I was wondering whether 2 bottles would be far too much. Thanks.
22 Jul 2016
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The Fernox F range of products are designed to treat 10 single panelled radiators, always count any double panels as 2 and always round up to the next complete bottle. So in your case you would need 2 cans (assuming that your 11 are all single panel?). After application ensure that the system is left circulating as the product reacts faster with warmth and needs to circulate to get to the source of the leak.
25 Jul 2016
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Brand Fernox
Colour Green / Blue
Manufacturer Guarantee 1 Year Manufacturer's Guarantee
Model No F4 Express
Pack Size 1
Pieces in Pack/Case 1
Product Depth 50 mm
Product Height 210 mm
Product Type Leak Sealer
Product Width 50 mm
Sealant Adhesive Volume 265 ml
Total Product Weight 389 kg

pH (concentrate): 5.0-7.0.

Hazardous - Delivery unavailable for any offshore location.

Product contents

Radiator and filling loop adaptors.


Safety Data Sheet (COSHH)