Indirect Cylinders
Used with central heating systems, these cylinders utilise a coil to seperate the domestic hot water and central heating water
Direct Cylinders
These cylinders do not posses a coil for water seperation and are only suitable for back boiler or electrical immersion heating
Vented Cylinders
If you have a gravity feed plumbing system your hot water cylinder will be open vented to prevent an pressure increase when heated
Sealed Cylinders
Sealed or Unvented cylinders are designed for use on pressurised plumbing systems and incorporate an expansion vessel
96 Litre (30"x18")
120 Litre (36"x18")
140 Litre (42"x18")
160 Litre (48"x18")
What size cylinder do you need?
The Hot water cylinder need to be correctly sized to meet both the demand and the heat source. For example a gas or oil boiler will heat the hot water cylinder quite quickly so the volume of stored hot water can be quite small (80 – 120 Litres).
Where a solar panel system will heat a quite a large volume of water for free in a short space of time dependent of course on the outside weather, therefore a solar cylinder will be quite large in comparison, often with a storage capacity of 300 Litres.
If you are unsure about your size requirement contact us and we will be happy to assist you in your decision making.
Key Sizing Considerations
- The amount of occupants
- The number of bathrooms
- The number of showers
- Heat Source (Gas,Oil, Solar, Electricity)
Cylinder Sizing Guide
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|---|---|---|---|
| 2 Bedrooms | 1 Bathroom | 1 Shower | 96 Litre |
| 3 Bedrooms | 1 Bathroom | 1 Shower | 120 Litre |
| 4 Bedrooms | 1 Bathroom | 2 Showers | 140 Litre |
| 4 Bedrooms | 2 Bathrooms | 2 Showers | 160 - 300 Litre |
| Larger Properties | 2 Bathrooms | 3 Showers | 300 Litre |
No. Of Bedrooms
No. Of Bathrooms
No. Of Showers
Cylinder Size
Hot Water Cylinder Guide
Open Vented Hot Water Cylinders
Open vented cylinders are usually manufactured from copper but are now commonly available in stainless steel. They are available in almost any size, grade and arrangement and usually 
come pre insulated unless otherwise requested.
The Higher grade the cylinder the longer the expected life span and durability, additionally you can expect a more costly installation. An open vented hot water cylinder is used in property’s that have a gravity fed plumbing system.
In a gravity fed system a cold water storage tank is placed at the highest accessible point, usually in the attic space. The water stored in the cold water storage tank supplies the hot water cylinder. The supply to the cylinder is reliant on gravity and care must be taken to ensure sufficient head of water. The cold water contained in the cylinder can then be heated and stored for use.
An open vent cylinder will have an open ended pipe that is routed form the hot water take off on the cylinder to above the cold water storage tank, this pipe acts as a vent pipe but more importantly maintains the low water pressure within the cylinder.
The pipe size should be no less than 3/4 inch and be constructed from a material capable of withstanding very higher temperatures (such as copper). It should not be constructed of Pex or plastic piping as in the event of a thermostat failure the water temperature can exceed the safe design parameters of Pex piping.
Unvented Hot Water Cylinders
Unvented hot water cylinders are used on pressurised plumbing systems, where the system pressure far exceeds that of a gravity system. They are manufactured from high grade stainless steel and are capable of withstanding very high pressures. A pressurised system is basically a water system that has a pressure pump installed. These systems typically have an 
operational pressure of between 2 – 3 Bar and are capable of delivering a very high flow rate. This high flow rate makes for a very satisfying user experience particularly where showering is concerned. Unvented hot water cylinders are available in a range of sizes and can be installed in both horizontal and vertical positioning with vertical being the most popular. Being a closed hot water storage tank safety is of the upmost importance, for this reason temperature and pressure relief valves are preinstalled on the cylinder. Additionally a potable water expansion vessel is also required, this allows for the increased pressure that will naturally occur as the water stored inside the hot water cylinder is heated. An annual safety check should be carried out, this ensures the operational performance of temperature relief valves, pressure relief valves and ensures the correct pre-charge pressure of the expansion vessel. You can expect a minimum 25 Year warranty on a good quality unvented hot water cylinder when maintained and inspected annually.
