How to Insulate Your Hot Water Tank: Step By Step

This step-by-step guide explains how to insulate your hot water tank. I recommend materials, provide safety tips, and highlight energy-saving benefits of fitting a cylinder jacket to your hot water cylinder.

What Tools and Materials Do You Need to Insulate Your Hot Water Tank?

To insulate your hot water tank effectively, you will need a British Standard (BS 5615) compliant hot water cylinder jacket with at least 80mm thick mineral wool or glass fibre insulation in a PVC cover, a flexible tape measure, strong string, cable ties or plastic straps, scissors or a sharp knife for trimming, protective gloves, and optionally pipe insulation foam lagging for exposed hot water pipes.

How Do You Prepare Your Hot Water Tank for Insulation?

Preparing your hot water tank for insulation starts by turning off the immersion heater at the wall switch or isolator and shutting off the boiler’s hot water supply, then allowing the cylinder to cool completely for at least 1–2 hours. 

Clear space around the airing cupboard or loft location, wipe the cylinder surface clean and dry, measure the height and circumference accurately to select the correct jacket size, and note any labels, thermostats, or controls that must remain accessible.

Step-by-Step Instructions for Insulating Your Hot Water Tank?

Insulating your hot water tank follows these straightforward steps for optimal thermal performance. 

Step 1: Position the jacket sections around the cooled cylinder starting from the back, ensuring full coverage without gaps while leaving clear access to the immersion heater boss, thermostat pocket, expansion vessel (on unvented cylinders), and pipe connections. 

Step 2: Secure the jacket snugly with the supplied ties or additional string, trim excess material neatly, and apply pipe lagging to any exposed primary flow and return pipes near the cylinder. 

Step 3: Finally, label the jacket with any important cylinder specifications and test the system by running hot water after restart.

What Safety Precautions Must You Observe When Insulating Your Hot Water Tank?

Safety precautions when insulating your hot water tank include never working on a hot cylinder to avoid burns or steam hazards, isolating all electrical supplies to immersion heaters or controls, avoiding coverage of pressure relief valves, temperature/pressure relief valves, or expansion vessels on unvented cylinders, and ensuring good ventilation in the cupboard or loft space.

Do not compress the insulation excessively, which reduces its effectiveness, and check for any signs of leaks or corrosion before fitting.

How Do You Check if Your Hot Water Tank Insulation Is Working Effectively?

Checking if your hot water tank insulation is working effectively involves feeling the outer surface of the jacket after the system has been running—it should feel only slightly warm rather than hot to the touch. 

Monitor your hot water recovery time and energy bills for improvements, and periodically inspect for gaps, sagging, or damage to the jacket that could compromise thermal performance.

When Should You Call a Professional Plumber to Insulate Your Hot Water Tank?

Calling a professional plumber to insulate your hot water tank is advisable if your cylinder is an unvented pressurised model, located in a difficult-to-access loft space, shows signs of corrosion or leaks, or if you are unsure about accessing electrical components and safety valves. 

Landlords may prefer certified installers to document the work for EPC assessments and tenant safety records.

Why YOu Should Invest in Boiler Cover Plans from Boilers 2 Go?

Boiler cover plans and boiler service plans from Boilers 2 Go deliver valuable protection for UK homeowners and landlords by covering annual servicing, breakdown repairs, parts and labour costs, and rapid engineer response for your boiler and hot water cylinder system. 

These plans help maintain efficient operation of your central heating and domestic hot water supply, extend equipment lifespan, ensure ongoing Gas Safe compliance for rental properties, and provide peace of mind against unexpected faults in immersion heaters, indirect coils, or cylinder-related issues.

FAQs

Why Should You Insulate Your Hot Water Tank?

Insulating your hot water tank significantly reduces standby heat loss from the cylinder, keeping water hotter for longer, lowering your gas or electricity bills, and improving overall home energy efficiency. UK households can save £40–£200 annually depending on usage, cylinder size, and existing insulation, with payback often in under a year. 

For landlords, better cylinder insulation supports compliance with Minimum Energy Efficiency Standards (MEES), helps achieve a higher EPC rating, and enhances tenant comfort in rented properties.

Before proceeding with DIY insulation, consider boiler cover plans and boiler service plans from Boilers 2 Go. These plans provide expert maintenance support for your heating system and hot water setup.

How much can I realistically save each year by fitting a cylinder jacket?

Most UK households save between £40 and £200 per year on heating bills after insulating their hot water cylinder, depending on household size, fuel type, and whether the cylinder was previously uninsulated or had only thin factory foam.

Does adding insulation affect the warranty on my hot water cylinder?

Adding a compliant external insulation jacket typically does not void manufacturer warranties on modern cylinders, but always check your specific model’s instructions or contact the maker, as some recommend against additional layers over factory foam.

Can I insulate pipes connected to my hot water cylinder myself?

Yes, insulating the first 1–2 metres of hot water pipes with 13–19mm foam lagging is a simple DIY task that complements cylinder insulation and further reduces heat loss.

How thick should hot water cylinder insulation be for best results?

The current UK recommendation is at least 80mm thick for loose-fit jackets to achieve maximum energy savings and compliance with best-practice standards.

Is cylinder insulation required for rental properties in the UK?

While not always mandatory, adequate hot water cylinder insulation (minimum 80mm) is strongly encouraged under energy efficiency standards and can help landlords meet or improve EPC ratings required by MEES regulations.

This comprehensive guide helps UK homeowners and landlords insulate their hot water tank efficiently while highlighting the advantages of professional boiler support. Explore boiler cover and service plans from Boilers 2 Go for reliable long-term protection of your home heating and hot water system. Always follow your cylinder manufacturer’s instructions and prioritise safety.