Signs Your Water Cylinder Needs Replacing 

We all need a hot water supply to our homes; typically, we take this for granted until something goes wrong. So it’s a good idea to keep an eye on your boiler and hot water cylinder, taking the time to perform regular maintenance and visual checks. 

But what are the signs your hot water cylinder needs replacing? Let’s take a look at some of the potential issues you could be faced with. 

Types of hot water cylinders 

First, we need to differentiate between vented and unvented hot water cylinders so you can determine which you have in your home. The primary difference between them is where the cold water is fed from. 

Vented cylinder 

A vented cylinder gets its cold water supply from a storage tank, usually found in the loft of your home. The water is fed to the vented cylinder by gravity which is why the cold water tank needs to be above the vented cylinder. The higher the storage tank the greater the water pressure will be. 

Unvented cylinder

An unvented cylinder is fed directly by water from the mains and does not require a cold water storage tank. These hot water cylinders will provide better water pressure than a vented cylinder.

Inside these two types of cylinders, there is either a coil which carries hot water supplied from the boiler and heats the cold water in the cylinder or a pair of immersion heaters. Some cylinders will have both where the immersion heater acts as a backup. 

Potential problems with hot water cylinders 

When your hot water cylinder reaches a certain age, usually between 10-12 years it is more likely to develop problems that may mean it’s time to replace it. 

No hot water

One of the signs that your water cylinder needs replacing is a lack of hot water. However, before you assume that this is a problem with the heating elements it’s a good idea to check the thermostat to see if it‘s set to the correct temperature. 

If the thermostat is working properly then there may be a failure within the cylinder’s heating system. Direct cylinders with immersion heaters at the top and bottom are prone to limescale buildup on these elements which can cause them to fail. 


Leaks are never a good sign so if you find water around the cylinder it is an indication that there is potentially a serious issue such as cracks in the tank, too much pressure or some corrosion. However, it could be something less drastic such as a failed or loose valve so get a certified plumber to check and diagnose the problem. 

Odd sounds

All cylinders will make noise as they heat the water inside. The most common is a popping sound which is caused by a build-up of debris in the tank. This is more likely in hard water areas where limescale will accumulate inside the tank. If you know you live in an area with hard water it is important to have an engineer flush out your system once a year. 

A high-pitched noise can be worrying but may be due to an inlet control valve not being fully open. Once it is opened, the sound should stop. 

Discoloured or smelly water from the tap

Perhaps the most obvious sign that your hot water cylinder needs to be replaced is if you get discoloured or smelly hot water coming out of your taps. 

Inside the cylinder is an anode rod designed to prevent corrosion in the hot water cylinder by attracting sediment and minerals. These rods are usually made of aluminium or magnesium but can fail over time as the minerals and sediment eat away at them. A sign that the anode rod needs to be replaced is cloudy and foul-smelling water coming from your hot water taps. 

If you suspect that there is a problem with your hot water cylinder you should get a certified plumber to take a look at it as soon as possible. Issues left unchecked can develop into much larger problems which may be expensive to rectify. When a repair is not possible or the hot water cylinder is no longer functioning efficiently it’s time to replace it. 

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