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Product Details

Ideal for sealing small leaks or weeping joints on all types of indirect central heating systems. Easy-to-administer solution and will not cause blockages within the system.

Technical Specification
Brand Sentinel
Safety Data Sheet click here
Volume (L) 1
Delivery details
Order value: Under £10 £10 & over
Express usually Next Business Day before 6pm £5 Free
Turbo usually Next Business Day before 12 noon £10 £5
Remote areas standard delivery (2-4 days) £5 Free
Order Value: Under £25 Over £25 but less than £75 £75 & Over
£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
If you are using our Click & Collect service please note the following:
  • Order online or over the phone and collect in branch from 5 minutes later.
  • Ensure you check stock is available for collection at your chosen branch.
  • Check branch opening hours to ensure you have sufficient time to collect.
  • For items not available for same day collection, place order before 8pm Mon-Sat (4pm Sun) and you can collect Next Business Day (Mon-Fri) after 3pm.
  • If we have your mobile number, we’ll send you a text when your order is ready to collect.
Sentinel Leak Sealer 1L is rated 4.9 out of 5 by 11.
Rated 5 out of 5 by from Very Happy Did the job just fine..quality
Date published: 2019-12-05
Rated 5 out of 5 by from Stop that Leak This is very good stuff. Had a leak in my central heating after changing some TVRs (valves). Could not stop some leakage after fitting one of them without draining down the system (again!). Purchased Sentinel after reading some reviews and thought I’d try it. Switched off the boiler and drained down one radiator which could be isolated and topped back up using this plus the system water that I collected. Fired the boiler back up and left for a few hours, checked for leaks and nothing. Note : If using this Leak sealer, fill system very slowly as it is thicker than water and can overflow easily, apart from that I really recommend it.
Date published: 2019-11-24
Rated 5 out of 5 by from Sealer Bought this as tried everything else works great.
Date published: 2019-11-22
Rated 4 out of 5 by from Appears to work I tried Toolstation for the first time, as this product was out of stock at several other similar suppliers. It is easy to apply, once you have gone online and read the instructions, as only limited instructions on the bottle. The tricky bit, if adding to a radiator, is removal of the application tube. Even though the radiator valves have been closed, there is enough residual pressure to squirt a little of the additive about 5ft or so, so you need to be dexterous with a wet cloth and fast when replacing the bleed valve. Best also to get the little black sealing bullet in the back of the tube to the bottle end at the start, as it can stick slightly in the tube. You will also need to cut the tube nozzle to be a precise fit to the bleed valve, otherwise any slight misfit under pressure causes leaks. The instructions on line could be a little better as the text is numbered but the related images are not.
Date published: 2019-11-21
Rated 5 out of 5 by from Amazing product This stuff is incredible but don’t expect an instant fix. I applied this directly to a cold radiator and then set the heating to come on. The boiler was still losing pressure and so I kept topping up to 1.5bar every time it dropped. The product needs time to cure but needs circulation so keep the pressure topped and then all of a sudden it took. The pressure jumped and has stayed constant
Date published: 2019-11-18
Rated 5 out of 5 by from Leak in central heating system Good product resolved the leak
Date published: 2019-11-14
Rated 5 out of 5 by from Does exactly what it promises !! A little sceptical as to wether it would work to cure pressure drop on my boiler but added to my system and now no pressure drop. 5*
Date published: 2019-11-01
Rated 5 out of 5 by from Does the job Had a leak on my heating tried anouther make didn't work this one did good very good product
Date published: 2019-10-28
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