Sentinel Internal Leak Sealer 1Ltr Product Code: 99730

Internal Leak Sealer for small inaccessible leaks and weeping joints in all types of indirect heating systems including those containing aluminium components. Compatible with elastomers.


  • 1 Year Guarantee
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Safety Data Sheet
Additional Information
Technical Specification
  • Brand : Sentinel
  • Sealant Adhesive Volume : 1 Ltr
  • Product Type : Internal Leak Sealer
  • Volume : 1 Ltr
  • Pack Size : 1
  • Manufacturer Guarantee : 1 Year Guarantee
  • Pieces in Pack/Case : 1
Product Contents
Delivery & Returns


Standard delivery service up to 3 working days: €8.95

Free delivery on all orders over €70.00

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Hopefully you won't need to return an item, however, if you do, it is our aim to make this as simple as possible. By following the guidance below you can help us to help you when a product is not what you expected, or is faulty. Your statutory rights are not affected by this guidance.


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€17.45 Incl. 23% VAT

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Sentinel Internal Leak Sealer 1Ltr is rated 4.7 out of 5 by 40.
Rated 5 out of 5 by from Miracle product Had this problem on my boiler where I had to top up couple times a week for a year. In that time I had replaced the pressure relief valve and a leaky diverter valve but no change. I then came across this ‘miracle’ product after reading a few reviews. Bought the product on the Sunday - I found it easy to pour it into an empty magna-clean (had to fill it twice if pouring all 1 litre of the product). Topped up the pressure and left it around 1 bar. Instructions does state that it can take 24 hours for it work around the system. Well it’s now Wednesday and the needle on the gauge has not moved. I can now honestly say that product does work.
Date published: 2017-11-01
Rated 5 out of 5 by from Great product Used this product the cure a underfloor leak in a sealed heating system via a towel rad advised customer to leave heating on for 4 hours after no pressure drop i would recommend this product along with inhibitor cheers
Date published: 2017-09-13
Rated 5 out of 5 by from Great product Great product works well.Easy to use.Was a bit reluctant to try it but happy I did stopped leaks instantly
Date published: 2017-07-30
Rated 1 out of 5 by from Did not work for me I have had an ongoing issue with a slow loss of pressure in my sealed heating system. Having spent hours checking every accessible joint, i could not find a leak and thought i would give this a try. Sealer was added as per the instructions but to no avail. I also noted a change in the tone of my boiler for a couple of days as it passed around the circuit. A friend suggested i tried Fernox F4 instead and it worked a treat. I guess you get what you pay for?
Date published: 2017-04-07
Rated 5 out of 5 by from Save on digging up the floors Had a tiny leak somewhere under the ground floor, so that the pressure kept dropping. No weep from the pressure valve, so I thought that I would try this stuff. 48 hours later it all looks good. Did a complete drain and flush before adding it using the simple filling kit into a radiator, together with the Sentinel inhibitor (which I had already bought). Can't give meaningful ratings for performance or reliability, as only 2 days into service.
Date published: 2016-12-20
Rated 5 out of 5 by from Sentinels little helper Great way to seal leaking push fit couplings when pipe is scratched.
Date published: 2016-12-11
Rated 5 out of 5 by from Well worth trying My 15 year old Worcester 24i combination boiler was losing pressure daily resulting in the overheat sensor tripping out. Told by heating engineer that must have a leak in system as nothing wrong with boiler. Assumed not in upstairs pipework or radiators as no sign of water damage. Did not fancy having to lift carpets and flooring down stairs to try and find leak. Bought Sentinel leak sealer to give it ago although a little sceptical it would work. BUT IT DID WORK. Boiler pressure now stable for last ten days. Only thing to be aware of is that it does not flow easily as is like thick PVA glue. So make sure if using tubing and funnel that it is large enough to flow easily. I drained system down enough to take off valve from upstairs radiator and fed tube into pipe. Worked for me. Better than lifting all the downstairs flooring! Happy days.
Date published: 2016-11-21
Rated 5 out of 5 by from Well worth the money I purchased this to sort out a small leak I had on my towel radiator, I removed the non bleed valve plug and used a length of tubing to remove a ltr of water, I then poured in Sentinel leak sealer, replaced the plug, turned on the system bled the radiator, hey presto no more leak. I would highly recommend this product to anyone who has the same problem.
Date published: 2016-11-08
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