Vented Hot Water System

Typical vented hot water cylinders (direct and indirect)

 

This is the standard solution many of us have in our homes, to provide hot water to taps and showers.

 

Water supply

The cold water is supplied to the vessel via a cold water storage tank, often located in the loft space directly above the hot water cylinder. A vent pipe runs from the top of the hot water cylinder and into the lid of the cold water tank above. This venting allows for the expansion of water in the cylinder via air bubbles and steam, and ensures the water is safely condensed to the cold water tank.

 

Water pressure

A standard vented system relies on gravity to supply hot water to the taps and shower(s), this means that the hot water cylinder must be located below the cold water storage tank, to generate the required ‘head’ of water pressure to adequately feed all outlets. To run a vented hot water system but supply higher pressure water to the taps and shower(s) will require the installation of a water pump into the plumbing system. Small twin-impeller pumps can be fitted to the water supply pipes for a single shower, or a larger pump can be used to provide high pressure water to an entire bathroom. Alternatively a centrifugal pump can be fitted which can provide high pressure water to the entire property.

Pros Can be fitted by a regular plumber or keen DIYer Cheaper than alternative storage systems Easier to maintain

Cons Requires a seperate cold water storage tank Gravity fed showers may require a pump if performance is unsatisfactory

 

Vented Combination Cylinders (vented and unvented)

These vessels are ideal for a small flat, or a property with a loft conversion where space is a premium in the loft area. Working to the same principle as standard hot water cylinders, combination hot water cylinders are a neat solution as they combine the hot water vessel and cold water storage tank into one unit.

combination cylinder

 

Water pressure

As with a standard vented system, a combination storage system relies on gravity to supply hot water to the taps and shower(s). As the cold water cylinder is located directly above the hot water cylinder, this means that the generated ‘head’ of water pressure is relatively low. To adequately feed all the draw off points (taps, showers), the combination system must be located above the level of the highest outlet, ie the water must flow down no matter how marginal the drop is. Be aware however that these combination cylinders are available in a limited number of sizes between 85 litres (19 gallons) and 210 litres (46 gallons) hot water capacity.

Pros Can be fitted by a regular plumber or keen DIYer Cheaper than alternative storage systems Easier to maintain

Cons Very low pressure/head which can cause problems for some showers Not very suitable for shower pumps as can empty too quickly