---
product_id: 207930694
title: "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"
brand: "coswarm"
price: "€ 200.58"
currency: EUR
in_stock: true
reviews_count: 13
category: "Cos Warm"
url: https://www.desertcart.hr/products/207930694-cw4-central-heating-leak-sealer-treats-up-to-18-radiators
store_origin: HR
region: Croatia
---

# Non-toxic & biodegradable formula Treats up to 18 radiators Stops minor leaks & pressure loss 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

**Brand:** coswarm
**Price:** € 200.58
**Availability:** ✅ In Stock

## Summary

> 💧 Stop leaks before they stop you — the smart fix for flawless heating

## Quick Answers

- **What is this?** 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 by coswarm
- **How much does it cost?** € 200.58 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.hr](https://www.desertcart.hr/products/207930694-cw4-central-heating-leak-sealer-treats-up-to-18-radiators)

## Best For

- coswarm enthusiasts

## Why This Product

- Trusted coswarm brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Eco & User Safe:** Non-toxic, biodegradable, and allergy-conscious for peace of mind
- • **Powerful Leak Sealing:** Seals small, hard-to-reach leaks without draining your system
- • **Metal-Friendly Chemistry:** Safe for steel, copper, aluminium & all central heating metals
- • **Super Concentrated Formula:** One 500ml bottle treats up to 150L or 18 radiators—max efficiency
- • **Effortless Use & Convenience:** No system shutdown needed; just pour and forget

## Overview

The CW4 Central Heating Leak Sealer is a super concentrated, metal-safe, and eco-friendly solution designed to seal minor leaks and fix pressure loss in central heating systems. Treating up to 18 radiators or 150 litres, it works without system shutdown and remains permanently in the system, saving costly repairs and downtime while protecting your boiler and the environment.

## Description

Free delivery and returns on all eligible orders. Shop 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.

Review: 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.
Review: Works well - Kept losing boiler pressure due to small leak under floor. A few days after treatment the pressure is fine.

## Features

- Contains benzisothiazolone. May produce an allergic reaction.
- Safety data sheet available on request.
- STOPS SMALL LEAKS & FIXES PRESSURE LOSS: CW4 Leak Sealer seals all the small and inaccessible leaks, thus saving time and money in draining down and repairing cost. Our boiler leak sealant also helps in fixing pressure loss due to minor leaks from central heating systems.
- SUPER CONCENTRATED FORMULA: Our boiler and central heating system leak stopper can treat up to 18 single radiators, i.e., a 150-litre system. It is easy to use, just pour it in the system according to the instructions and let it work.
- HARMLESS FOR METALS: There are many leak sealant chemicals that are not friendly when they come into contact with metals. CW4 Leak Sealer liquid is suitable for use with all the metals and materials, including steel, ferrous metals, copper and aluminium.
- CONVENIENCE AT ITS BEST: Our leak sealer and stopper makes minor repairs in the boiler a breeze. It does not interfere with the working of your central heating systems and you won’t have to shut down the systems before or while using it. The product can be left in the system permanently.
- SAFE FOR YOU, THE BOILERS & THE ENVIRONMENT: Our non-toxic radiator leak sealer is a safer alternative compared to other toxic, chemical formulas. As it is biodegradable, it won’t harm Mother Nature either. Safe to use around people, the environment and your heating systems.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| 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 |

## Images

![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 - Image 1](https://m.media-amazon.com/images/I/71zDWDxQPuL.jpg)

## Customer Reviews

### ⭐⭐⭐⭐⭐ Did the job!
*by R***M on 5 April 2022*

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.

### ⭐⭐⭐⭐⭐ Works well
*by K***. on 22 December 2021*

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

### ⭐⭐⭐⭐ OK for small pressure loss,but sadly no help for me.
*by A***R on 20 March 2023*

Leak on garage radiator tap.

## Frequently Bought Together

- 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
- QuickFill - SEL9260: Central Heating Dosing Tool - Add Chemicals Like Fernox Central Heating Inhibitor, Sludge Remover, Leak Sealer & Sentinel X100 to Your Central Heating System

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**Shop now:** [https://www.desertcart.hr/products/207930694-cw4-central-heating-leak-sealer-treats-up-to-18-radiators](https://www.desertcart.hr/products/207930694-cw4-central-heating-leak-sealer-treats-up-to-18-radiators)

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*Product available on Desertcart Croatia*
*Store origin: HR*
*Last updated: 2026-03-10*