






🔥 Seal leaks, save time, and stay warm—effortless heating peace of mind!
CW4 Central Heating Leak Sealer is a super concentrated, non-toxic formula designed to seal minor leaks and fix pressure loss in central heating systems. Treating up to 18 radiators (150 litres), it works without system shutdown and is safe for all metals and the environment, offering a hassle-free, eco-friendly solution to common boiler leaks.







| ASIN | B088JYB6JZ |
| Batteries Required? | No |
| Batteries included? | No |
| Best Sellers Rank | 326,032 in DIY & Tools ( See Top 100 in DIY & Tools ) 3,167 in Sealers |
| Customer Reviews | 4.0 4.0 out of 5 stars (531) |
| Date First Available | 12 May 2020 |
| Item Weight | 453 g |
| Manufacturer | CosWarm |
| Manufacturer reference | CosWarmCW4 |
| Package Dimensions | 18.2 x 8.6 x 5.8 cm; 453.59 g |
| Part Number | CosWarmCW4 |
| Size | 500ml |
R**M
Did the job!
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.
K**.
Works well
Kept losing boiler pressure due to small leak under floor. A few days after treatment the pressure is fine.
A**R
OK for small pressure loss,but sadly no help for me.
Leak on garage radiator tap.
A**A
Central Heating fluid.
My husband was very pleased with this item.
A**R
Leak sealant- stopped the leak
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?
A**S
Unfortunately this did not work for me,
Still losing pressure over the space of a week, have a large heating system added two bottles
A**.
Didn't use it
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.
D**R
Really works
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.
V**E
Produit pour colmater un trou
Excellent produit Ça a fonctionné du premier coup Pour un trou dans un radiateur en acier Super je recommande
T**O
Geen drukverlies meer in CV
Mijn vloerverwarming had een lekkage, wist niet of dit ook geschikt was voor vloerverwarmingsslangen maar daar lijkt het wel op. Na dit middel te hebben toegevoegd hebben wij geen drukverlies meer. He wel voor de zekerheid de slangen goed doorgespoeld met schoon water voordat ik het erin deed.
R**A
Heizung
Ein Leck in der Heizung, kein Problem nehmen Sie CosWarm CW4 LeakSealer und alles ist gut. 👍 Sehr zu empfehlen.
F**.
Funciona
Escribo esta reseña tres meses después de comprarlo y usarlo. Tenía una fuga en el circuito de calefacción en la parte baja de la casa que daba la cara. Después de venir técnicos con cámara de calor térmico, técnicos de la caldera cambiándole múltiples piezas incluido vaso de expansión porque la presión bajaba 0.7 cada 12 horas, vamos todo el invierno metiendo presión dos veces a la caldera. He gastado mucho dinero, como he dicho anteriormente, ya que la fuga no daba la cara y podía ser de múltiples sitios. Al final me decidí comprar este producto, el cual he echado con una jeringuilla por un lado del purgador del radiador, siguiendo las instrucciones que había puesto en un comentario por aquí alguno y poco a poco la caldera ha ido corrigiéndose y he de decir que al principio tuve que meterle agua a la semana después le metí agua a los 10 días y no he vuelto a meterle agua inclusive ahora en verano la presión permanece estable . Ojalá dure, pero llevando ya tres meses con el producto echado solucionado el problema. No he querido compartirlo antes, ya que supongo que toda la gente que buscamos este tipo de productos queremos saber si funciona realmente y yo hasta que no he comprobado que era así no he querido escribirla.
W**G
good , worked!
I have a 24 rooms motel with a 20 years old boiler, add few bottles cw4 and cw1 , no more leaking. Thanks a lot. from Alberta canada.
Trustpilot
1 week ago
1 month ago