Unvented Water Cylinder Engineers
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Electric Hot Water Heater & Unvented Hot Water Cylinder Installation
New Pipes
Connecting new Cyclinder
Installation
Hot water systems explained
Traditionally the delivery of hot water to appliances in domestic properties relied on gravity. The pressure delivered at the tap or appliance relies on the height of the cold water tank above the highest outlet. This is usually the shower on the top floor of the property. With gravity systems you can notice the increase in water pressure if the shower head is held low down close to the shower tray.
Components of systems designed for use in gravity systems are not suitable for use in mains pressure systems. For example in addition to changing the hot water storage cylinder you may have to change the shower cartridge to enable it to cope with the increase in pressure, the valves on the toilets in the case of balanced pressure and possibly other the cartridges in other outlets.
There are two types of mains pressure hot water system
- Unvented Mains Pressure
- Vented Mains Pressure (Thermal Stores)
The term vented refers to whether the system is vented to atmosphere or closed to the atmosphere and therefore pressurised. It is because unvented systems are closed that special safety precautions have to be taken. Without these precautions the water within the system could become over heated and over pressured with disastrous results
The Positives of each type of hot water system
Unvented Mains Pressure
- Mains pressure hot water to all taps
- No tanks required, saving space in loft
Thermal Store (vented mains pressure)
- Mains pressure hot water to all taps
- No specialist installation requirements
- Does not require an annual service
- Building control does not need to be notified
- No tanks required, saving space in loft
The Negatives of each type of hot water system
Unvented Mains Pressure
- Requires specialist installation
- Annual service required
- External discharge pipework required
- Installation requires notification to Building Control
Thermal Store (vented mains pressure)
The negative aspects of thermal stores also apply to all mains pressure water heaters
When the valve was inspected the EasyFlow engineer noticed that the original installation was incorrect. If you look at the photo titled ‘Faulty and Incorrectly Installed Valve’. The single check valve installed (and partially hidden by the cylinder) should not have been installed after the expansion valve.
General information about water pressure
Properties with mains pressure water systems will have mains pressure at all hot taps and water appliances. This can also apply to cold water. This is achieved by first taking the supply for the hot water directly from the incoming water supply and then taking a branch pipe off this for the cold supply. From this point on there are two sets of pipes in the property; one for hot water and one for cold. Both sets of pipes are directly connected to the main supply and both rely on the main supply for their pressure and flow. The cold pipework provides the supply to the cold water outlets, the other passes through the hot water cylinder and from there to the hot side of the system. A balanced system, where the hot and cold water are delivered at the same pressure, have the hot and cold water branches at or just after the pressure reduction valve. An unbalanced system will have the cold water supply branched off before the pressure reduction valve.
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