Vented Hot Water Cylinders

Vented Hot Water Cylinders (Traditional)

What Is A Vented Hot Water Cylinder?

Vented hot water cylinders are considered the traditional, and probably most common form of providing hot water to domestic properties.

They are fed by a cold water storage tank, most commonly sited within a properties loft space. The cold water storage tank replaces the water within the cylinder as it's drawn off. The hot water system is under atmospheric pressure (the natural pressure around us), as the tank is open to the atmosphere. This means that the water within the system is free to expand, by use of an 'open vent' pipe, that runs up to and above the cold water storage tank, hence the term 'vented cylinder'. Therefore, the water is delivered under the natural, 'gravitational' pressure available, which is determined by the positioning (height in relation to draw off point -(head)) of the cold water storage tank.

Due to their simplicity,- and that they are able to expand when heated,- they are one of the more simple systems to install, of the systems available. There are many forms of vented cylinders, some of which are listed below.

Positives Of Vented Cylinders

So the positive aspects of vented cylinders are that 1. They are open to the atmosphere and therefore naturally very safe, because they are not pressurised. 2. There is little requirement for safety devices to ensure safety. 3. There is no need for an expansion vessel to take up the expansion of the water, as it is open to the atmosphere. 4. If the tank is high within the property and pressure therefore good, then several draw off points can be used at once, with little effect on each other (if pipe work has been sized correctly).

Negatives Of Vented Cylinders

The negative aspects are 1. Performance is largely dependent upon the fitting of the cold water storage tank, and it's height in relation to draw off points (taps). 2. Showers fitted in bathrooms located just below the water level in a tank which is located in the loft just above, often have poor performance (pressure & flow rates). 3. This gives rise to the need for a booster pump/(s), to be fitted to shower supplies, to give adequate performance. 4. Vented cylinders in flats often suffer from poor pressure especially, often with no loft space available (see the combination cylinders below, often used in flats with no loft space).

Below is a diagram of a complete open

vented hot water and heating system (indirect),

(the cylinder hot water is heated indirectly

by a separate open vented boiler).

Below is a diagram of a direct combination unit.

(Electric immersion heaters would be fitted into

the two bosses shown at the front of the

cylinder, and heat the water directly).

- Very commonly fitted in flats with no loft space.

Gledhill - Cylinder Manufacturer

Our most commonly used manufacturer for open vented cylinders is Gledhill. They manufacture the complete range of open vented cylinders in both copper and stainless steel, be it direct, indirect, cylinder only, or combination units, plus many more,..they can all be manufactured to specific requirements, if required.. This includes a full range of options available with each type of cylinder, such as high recovery heat exchanger coils (reheat times in as little as 15 minutes), compression or female thread tappings as required, tappings in specific places etc.

Click Here To Download the Gledhill P.D.F Vented Cylinder Brochure

Below is a picture of a standard, Gledhill,

'Envirofoam' lagged, indirect, copper, vented hot water cylinder

(our most commonly fitted cylinder).