Home
Up

A guide to different plumbing system types
The Shower Right guide to product and system compatibility
Before making any decisions, or indeed a purchase, it is wise to familiarise yourself with the type of system to which you will be adding components. Whilst we are always at the end of a telephone to provide help www.showerright.co.uk respect your desire to quietly research the subject. For this reason the following guide will provide you with a grounding in the various types of water system and the appropriate products for connection. Remember, this is a guide an not intended to be a definitive instruction manual.

 

How to identify your system

When you are considering installing, upgrading or revamping a shower room or bathroom it is important you understand what type of water system you have and what equipment you may use (or need to use) as a consequence.

Over the years as the technology behind heating and storing water has developed so have the various components and ancillary controls required to allow the system work correctly.

To be able to select the correct type of product for your installation it is essential you understand the type of water system to which you intend to connect.

In the UK there are two basic methods of supplying water to outlets in the average household scenario (these examples assume the property is supplied from a water main rather than a borehole, well or water storage tower).

Method 1: A Gravity System - Probably the most common hot water system in the UK. This type of system requires incoming mains pressure water to be delivered to a holding tank, often situated in the loft of a house. Water from this tank (commonly known as a header tank) is fed down to a storage cylinder (sometimes referred to has the hot water cylinder) which is often sited in a small cupboard which many of us know as the airing cupboard. The contents of the hot water cylinder may be heated by an external heat source such as a boiler, or by an internal heat source such as an immersion heater. No matter which method is employed to heat this configuration of hot water system it remains open vented, relying only on the height of the water in the header tank above the outlet point to create pressure.

 Visit our sister website www.gasapplianceguide.co.uk for a comprehensive range of discounted heating products, including vented and unvented hot water cylinders.

Cold water may also be delivered to various outlets in a property from the header tank in a loft, although there are various practical and operational reasons why this is not always a good idea. It is more common to have cold water delivered to outlets by the following method even if the hot water is a gravity system.

Method 2: A Mains Pressure System - The most obvious way to feed incoming cold mains water directly to the outlet point will be to pipe it straight to a tap for example. This is fine if you only want cold water on tap, but what about hot water? It is the method by which you heat and store hot water that becomes an issue.

If you wish to heat, store or deliver hot water at mains pressure you are deemed to have a 'high pressure', 'mains pressure' or 'pressurised' hot water system. Whilst this type of system may offer better performance in terms of pressure and flow there are serious issues with safety and types of outlet (showers for example) that must be addressed.

Mains fed hot water systems can be broken down into two basic categories

  1. A system that heats hot water on demand, requiring no storage vessel, or

  2. A system that stores a volume of hot water in much the same way as a gravity system but keeps it under mains pressure.

The first type of system is usually referred to as a Combi Boiler (which has central heating capabilities) or a Multipoint (that tends to only heat hot water on demand for bathing purposes). Both types heat water as it passes through the unit.

The second type of system, whilst vaguely resembling a gravity system at a glance is a very different animal.  Water stored within the unit is still heated by internal or external heat sources but is kept at mains pressure by a direct connection to the rising cold water main. The storage vessel (or cylinder) required to withstand the forces exerted on it by water under mains pressure is very different to a gravity cylinder.

Note: NEVER connect a mains pressure cold water supply to a cylinder specifically designed for connection in a gravity supply system (one with a header tank). The results can be catastrophic and may result in severe injury and/or death.

Mains pressure hot water systems are invariably more expensive to install that a gravity system, but generally provide greater performance (where the hot water becomes as good as the cold water supply).

Using the guidance notes below, select the system in your house or, if you are still unsure what you have, select the options for more information or consult a professional plumber.
Gravity Hot Water system
  • Cold water tank in the roof
  • Lagged hot water cylinder in airing cupboard
  • Mains pressure flow only from cold kitchen tap

 
High Pressure sysytem
  • No water storage tank in the roof
  • High flow and pressure of water from all taps
  • system installed since 1986 (these systems were not used before this date)

 
Combination Boiler system
  • No hot or cold water storage in the house at all
  • Commonly used in 1-2 bedroom houses and flats
  • Boiler operates on demand
 

 

 More Information about Gravity Hot Water Systems

What it is and how it works A gravity system takes water from the mains and stores it in a tank at the top of a building. The water is then fed in to the plumbing system under gravity. This cylinder will commonly have foam lagging round it and is commonly located in the airing cupboard. A vast number of houses in the UK have this type of system.

 

Selecting a shower for this system

  • Choose a mixer shower with a high flow rate to ensure a powerful flow.
  • A thermostatic shower is strongly recommended to avoid the risk of scalding if a toilet is flushed or a tap turned on.
  • You can use a pump to improve the flow rate of this kind of system (Note: A pump may only be installed to a gravity system. You may not, under Water Bye Laws, install a pump on a Mains Pressure system).

 Common pitfalls to watch out for

  • Selecting a cheap imported shower which is only designed to work on mains pressure. Choose only showers designed for the UK water system.
  • Selecting too large a showerhead or multiple outlets without a pump to achieve the necessary water pressure to make these items work properly.

 More Information about Mains Hot Water Systems

What it is and how it works A mains pressure system takes water directly from the mains and supplies it to both the hot and cold systems. Heated water is stored in a special hot water storage cylinder built to withstand the pressures of mains hot water. These systems were introducted into the UK relatively recently. A typical cylinder is called a "Megaflow", made by Heatrae Sadia.

Modern technology has developed a Vented Cylinder which can now provide Mains Pressure Hot Water - Known as a Thermal Store (such as The Torrent and Torrent RE).

 

Selecting a shower for this system

  • Because the water is at mains pressure already, the system requires no pump to achieve power shower performance
  • Shower valves will give a reasonable performance as the mains pressure will ensure a forceful flow of water
  • We recommend you use a thermostatic valve, but you may wish to consider a Pressure Balancing Valve to achieve the same safe showering

Common pitfalls to watch out for

  • You cannot fit a pump to this system (it is illegal in the UK)
  • Check that the valve you use is rated for use up to the mains pressure and fit a pressure reducing valve if needed.

 

 

 More Information about Combination Boiler Systems

What it is and how it works

A Mains pressure system takes water directly from the mains and supplies it to both the hot and cold systems. The hot water is heated as it is used by the boiler and therefore there is little or no stored hot water in the system. This can limit the flow available but is arguably economical to run. This type of system is common in flats or small houses where the low flow rate is not an issue or where space and/or a loft mounted header tank is a problem. Multipoint water heaters are similar to combination boilers but only provide water to taps and showers not radiators.


Selecting a shower for this system

  • Because the water is at mains pressure already, the system requires no pump to achieve power shower performance.
  • Most showers give a reasonable performance, but some cheap combi boilers have such a low flow rate that there can be problems.
  • We recommend you use a thermostatic valve, but you may wish to consider a Pressure Balancing Valve to achieve the same safe showering.


Common pitfalls to watch out for

  • You cannot fit a pump to this sytem (it is illegal in the UK).
  • Some valves are not compatible with some types of combination boilers, particularly those with step modulating burners. If in doubt call us or consult a qualified plumber to check the compatibility.

 

 Electric Shower versus Mixer Shower

Before you commit to an electric shower, you should consider the pros and cons of mixers and electric showers. Electric showers have advantages but they are not as cheap to install or run as they may appear at first glance.

Use the guidance notes and then choose which option you want to opt for.

 Mixer Showers

 Electric Showers

Advantages

A much more powerful flow rate, especially if pumped

Neat, stylish appearance

Uses your existing hot water system, which can be more economical than using electricity to heat the water

More reliable, with a longer guarantee

No need for a dedicated high capacity electrical supply

Advantages

Heats the water continuously, so you never run out of hot water

Inexpensive to buy

Disadvantages

Could run out of hot water if there is heavy demand on the system

More expensive to buy, though often cheaper to install.

A mixer shower is the best system to have unless cost or water usage is an issue.

Disadvantages

Flow rate is generally much lower than a mixer shower, especially in winter when the incoming water supply is cold

More bulky in the shower than a mixer

Requires installation of a high capacity electrical supply direct from your fuse box on its own dedicated circuit. This can be costly.

A good option if you want something economical or for a second bathroom that is used at peak times only