CosWarm CW4 Central Heating Leak Sealer - Treats Up to 18 Radiators - Stops Leak - Boiler Leak Repair & Sealant - Stops Minor Leaks & Weeps, Fixes Pressure Loss & Leaking Pipes - Underfloor Heating

Used for a very small leak on bathroom radiator union pipe. Worked first time. Pour in, run heating, seal leak. What’s not to love?

Kept losing boiler pressure due to small leak under floor. A few days after treatment the pressure is fine.

Leak on garage radiator tap.

My husband was very pleased with this item.

I had one small leak from one radiator out of six.I put the full bottle into the tank.It did not stop the leak.I have left it in for over a week nowand the radiator is still leaking.Will not buy again do not wast your money.Will now buy a new radiator.

I bought this as the water pressure kept dropping in my boiler and I could not find the reason. This was suggested for treating small leaks in hard to find places. However, the day after I ordered it I found the leak and after speaking to a plumber this was not going to help. One thing I would say is that it is only the bottle is supplied and I couldn't work out how to get this into the heating system. Looking else where you are probably going to need some sort specialised funnel.

We had a very small leak on a radiator valve and bought this to see if it would stop the leak rather than draining the system and replacing the valve. It worked a treat and no more leak.

This product really works, had a small leak in boiler and had to top up every 2 days. it sealed the leak within 2 hours.