Technical guides
What we know about hot water storage, written down: how to choose a cylinder, how to design safe and efficient storage, and the regulations and standards that apply. Each guide answers one question, for the people who ask it.
Choosing a cylinder
For homeowners and installers deciding what to fit, and what to fit in place of a range that has gone.
Designing hot water storage
For specifiers, M&E consultants and commercial installers: getting the stored water hot, safe and efficient.
- Stratification in thermal stores, buffer vessels and calorifiersHow do diffusers, sparge pipes and baffle plates keep the hot and cold layers apart?For specifiers and M&E consultants
- Legionella and safe hot water storageWhat temperatures and design details keep stored hot water safe under HSE L8 and HSG274?For specifiers, installers and building managers
- Cylinder and calorifier insulationWhich insulation and finishes are available, and what difference do they make to heat loss?For specifiers and procurement
Regulations and standards
The rules a cylinder or calorifier has to meet, and how ours are built to them.
- Building regulations for cylinders and heat pumpsWhat do Part L, Part G and Part P ask of a hot water cylinder, and what changes in 2026?For installers, specifiers and homeowners
- Calorifier manufacturing standardsWhat do BS 853, PD 5500 and the Pressure Equipment Regulations mean for a calorifier?For specifiers and procurement
Short answers
Quick explainers from our product pages, one question each. There are more, including our TechTalk series, in Insights: technical advice.
- Choosing the right domestic hot water cylinderWhat size and type of hot water cylinder does my home need?
- The advantages of unvented hot water systemsWhy choose an unvented hot water cylinder?
- When a vented cylinder is the right choiceWhen is a vented cylinder better than an unvented one?
- What a thermal store doesWhat is a thermal store and how does it work?
- Horizontal cylinders for restricted heightCan I fit an unvented cylinder where there isn’t the height for an upright one?
- Cylinders engineered for heat pumpsWhy does a heat pump need a special hot water cylinder?
- Twin coil cylinders for two heat sourcesHow do I connect a boiler and solar or a heat pump to one cylinder?
- Why install a buffer vesselDo I need a buffer vessel with my heat pump or boiler?
- Why use a low loss headerWhat does a low loss header do?
- What’s in an unvented cylinder kitWhat safety components come with an unvented cylinder?
- Why approved unvented components matterCan I use non-approved parts on an unvented cylinder?
- Calorifier manufacturing standardsWhich standards should a calorifier be built to?
- Gasketed vs brazed plate heat exchangersShould I choose a gasketed or a brazed plate heat exchanger?
- Cylinder and calorifier insulation optionsHow should a cylinder or calorifier be insulated?
Tools and documents
- Design toolsSizing, heat loss, will-it-fit and replacement finders
- Manuals & datasheetsWhat we publish for each product, no login
- Resources for specifiersDatasheets, certificates and specification text
A question none of these answers? Email sales@whcylinders.co.uk or call 0161 343 8610 and our technical team will talk it through.
Need a cylinder built to your specification?
From 10 litres to 10,000 litres, our Manchester team designs, manufactures and tests every vessel in-house. We confirm and respond to every bespoke enquiry within 48 hours, and standard range enquiries immediately. If you need a price on a standard product, don’t hesitate to call and speak to one of our team on 0161 343 8610.We confirm and respond to every bespoke enquiry within 48 hours, and standard range enquiries immediately. If you need a price on a standard product, don’t hesitate to call and speak to one of our team on 0161 343 8610.We confirm and respond to every bespoke enquiry within 48 hours, and standard range enquiries immediately. If you need a price on a standard product, don’t hesitate to call and speak to one of our team on 0161 343 8610.