Unvented Hot Water Systems (Megaflo)
Unvented water heating is the fastest growing sector of the UK market, led by Heatrae Sadia's Megaflo eco. Unvented systems are fed directly from the cold water mains supply and offer a number of benefits compared to conventional systems. Higher pressure and flow rates at all hot taps, balanced hot and cold water supplies, no special taps required.
An unvented system requires many safety devices to accommodate the greater pressure and expansion of water. If these safety devices are not correctly installed, the system will be unsafe and could be extremely dangerous to use. The installation of an unvented hot water system must be installed by a properly qualified plumber, who has an unvented hot water certificate.
While unvented cylinders are frequently called Megaflos, a Megaflo is actually a particular brand of unvented cylinder. Similar to a Hoover being synonymous with a Vacuum Cleaner! Megaflo is the market leader with a proven track record, backed-up with a lifetime warranty!
Today most new homes have unvented systems installed as standard and all major manufacturers now offer unvented cylinders, such as Megaflo (Heatrae Sadia), Telford Stainless Steel, Ariston, MODUS, etc
There are major advantages to be gained with an unvented hot water system - powerful and invigorating showers (without the need for noisy pumps), balanced hot and cold water delivering superb flow rates to modern mixer taps.
How Does It Work?
Unvented or high pressure hot water cylinders are powered by mains pressure water, rather than the head of pressure created by a water cistern in the loft. This means that in most cases you will benefit from stronger hot and cold water from your bathroom taps and showers, as well as no longer needing a large water tank in the loft.
Typically, the kitchen cold tap will be supplied directly from the mains and therefore usually has good water pressure. With an unvented hot water cylinder, you will achieve similar pressures from all taps - both hot and cold.
Hot water is stored in the cylinder at mains pressure. In other words, the cold water mains is connected directly to the unvented cylinder. When a hot tap is opened, hot water is forced out by the incoming cold water which replaces the hot water being pushed out. There are no cold water storage cisterns, vent pipes or expansion tanks, but instead, cold water is supplied at mains pressure into the cylinder, thereby supplying hot and cold water to the entire property at mains pressure. A pressure vessel allows for expansion as the water is heated, via a flexible diaphragm.
Without getting too technical, an unvented cylinder relies on the incoming mains pressure water and flow rates. There are no moving parts and if correctly installed, provides a reliable and efficient hot water system. There are a number of safety devices which are essential to ensure safe operation.
Will It Work For Me?
This is the important bit!
The first consideration is the water pressure and flow rate at your property. Mains pressure varies from area to area it is essential that we measure the available pressure at your property and discuss your requirements before you have an unvented cylinder fitted. If the pressure is 1.0 bar and above, then you should be okay, but there other factors to take into consideration.
Pros and cons associated with unvented hot water
systems:
| Pros | Cons |
|---|---|
| High pressure supply to all hot and cold outlets allow for more flexible system design. | If your house is supplied with a water main that has poor pressure and water-flow it may not perform correctly. |
| Balanced hot and cold water supply pressures throughout the system. | There is no back-up water to fill the cistern once emptied if the water main fails. |
| Cylinder can be sited almost anywhere within the property. | The space an unvented system and its components take up is generally larger than that of a conventional cylinder. |
| Flexibility allowing a wider choice of taps and mixers. | The initial installation cost of the unvented cylinder can be higher than a conventional system. |
| High performance showers without the need for pumps. | |
| No cistern in the loft (no risk of water stagnation, no risk of frost damage to pipework, no noise of filling cisterns). |
Apex Plumbing and Heating are fully qualified to install and commission unvented hot water systems.
Please contact us for further details or to arrange a no obligation written quotation.