web site updated 28 January 2012 © Lovekin Ltd 2009-2012 registered in England & Wales No.3950749 2 Ashdene Crescent GU12 6TA 01252 334440
We're developing this Web site to provide a review of the types of shower available for domestic properties. We'll be looking at:
- Gravity showers, based on a cold water tank in the loft and a conventional hot water cylinder
- Pumped power showers, with the pump either integrated into a wall unit or located separately
- Electrically heated mains pressure showers, not the best power shower but cheap to install
- Power showers run from combination boilers or from multipoint water heaters
- Venturi power showers, using the power of the potential energy stored in mains cold water to draw in low pressure hot water
- Power showers run from unvented hot water cylinders like the Megaflo™
- Power showers run from thermal store cylinders like the Albion Mainsflow™
We'll also take a look at shower heads and riser rails, thermostatic shower mixing valves, shower enclosures, shower trays and wet rooms.
But before you start, please read our legal disclaimer
A guide to the different types of showers available
gravity showers, electric showers and power showers
The information provided in these pages is given in good faith and is only designed to provide an overview of the subject. We can accept no liability for any damage or injury sustained in connection with the installation or use of any shower system, nor any liability arising out of misleading, incomplete or incorrect information on this site.
Aside from starting this power shower guide, Lovekin Ltd service and repair domestic gas boilers in the UK in the area around Guildford, Camberley, Aldershot, Farnham, Wokingham, Godalming and Woking. We also carry out gas boiler installation and gas boiler replacement. For more about how and where we work, visit our lovekin boiler service web site
For more about us see our
lovekin boiler servicing web site
Power Shower Guide ~ Powershower Guide ~ Power-shower Guide ~ Power Shower Options Explained ~ Which Power-shower? ~ Domestic Powershowers
Though they're not power showers we've decided to include gravity showers partly to provide a benchmark against which to compare power showers and partly because they have significant plus points.
Taking the obvious negative point first, gravity showers generally lack power, providing low flow rates and a weak spray but this isn't always the case. If a gravity shower is sited on the ground floor of a house and the cold tank which supplies water for the shower is in the loft, good shower flow rates can be achieved, particularly if the right shower head, mixing valve and pipe sizes are used.
In hard water areas lime scale is a problem but that applies to power showers too and we'll look at lime scale later.
- gravity showers are simple, with no pump and less to go wrong
- gravity showers can be cheap to install and are cheap to run
- gravity showers are green. The lower flow rates mean they use less water and less energy to heat the water so the impact on the environment is limited. Environmental factors are inevitably going to become more important over the next few years.
Cold water in main storage tank
Ball valve
Mains cold water in
Shower head
Shower mixing valve
Stored water in the cylinder is heated by a boiler (gas, oil or solid fuel) or by an immersion heater
Hot water to taps
How Gravity Showers Work
When the shower mixing valve is opened cold water falls from the cold water storage tank in the loft, passing through the mixing valve and out of the shower head.
At the same time cold water falls from the loft tank into the bottom of the hot water cylinder. It pushes hot water stored there up and out, into the shower mixing valve and out of the shower head.
By adjusting the shower mixing valve you control the temperature and the flow rate or the water coming out of the shower head.
Gravity Shower Plus Points
The flow rate of a gravity shower depends on a number of factors. The bigger the distance vertically between the shower head and the level of water in the cold tank, the faster the shower will flow. Extra height adds far more than the extra resistance in the pipes but horizontal pipe runs just add resistance and should be kept as short as possible. In flats where the cold tank can't be sited in a loft, gravity showers give very poor flow rates and in flats where Fortic™ type cylinders are used (these have a
Flow Rate Factors
small cold tank built directly onto the top of the hot water cylinder) gravity showers are almost useless.
Flow rate also depends on pipe sizing, the bigger the pipes the better. Different pipe materials can be significant; some of the newer plastic pipes are very smooth bored and have low resistance to water flow. They can also be "cabled" through in continuous lengths with very few joints. All pipe joints add significant resistance and for best results with copper pipes the pipes should be fully de-burred.
The type of shower mixer valve and shower head is also important. Some manufacturers make shower equipment with low flow resistance specifically designed for gravity showers. If the shower spray head can be hand held you should ensure that the shower hose connected to the head has the largest bore possible. The bore of shower hoses varies enormously with some having a bore whose cross-sectional area is 4 or more times larger than others.
Bath/shower mixer taps are not ideal as the bore through them is generally very small so the resistance is high. Some bath/shower mixer taps now suggest a minimum pressure needed to operate the shower adequately. If the box says the mixer needs 1 bar head of pressure you need a water tank about 33 feet (10 metres) above the shower head. With significantly less water pressure, flow rates may not be the only problem; the diverter valve in the mixer taps is often held in the shower position by water pressure and with low pressure it may refuse to stay in the shower position.
More on Flow Rates - Gravity Showers
To get a good gravity shower everything must be done to maximise flow. A high flow shower head should be used. It may be possible to enlarge the holes in the shower head.
Thermostatic mixer valves limit temperature fluctuations in the shower but they may significantly reduce flow. This poses problems for gravity showers and it's worth considering a manual (non-thermostatic) mixer valve.
The risk is that someone draws off cold water while you're using the shower (eg flushes a loo) and cold to the shower is reduced, scalding you. One way round this is to run an independent cold pipe directly from the cold tank; if someone uses the hot water you may be chilled but not scalded.
Independent hot pipework can be run to prevent this but the hot flow rate also depends on the size of the cold pipe from the cold tank to the bottom of the hot water cylinder. If a large bore pipe is used here, and an independent hot pipe from cylinder to shower, temperature variations can be minimised.
Finally, if flow matters more than looks, use two full-bore lever valves in place of a mixing valve, one on the hot and one on the cold. Tee them together and use a fixed shower head with enlarged holes. It may not be pretty but it will be quiet, reliable, have good flow rates and be much less susceptible to lime scale problems. Back to the Top
Electric showers use mains pressure cold water and don't need a stored hot water supply. The heating unit is contained within a small packaged shower unit attached to the wall. The heating element is several times more powerful than an electric kettle, allowing the water to be heated from cold as it passes over the element.
None of the electric showers currently available can produce flow rates comparable to the other power showers but they can be cheap to install.
Electrical Requirements
A heavy duty electrical cable is required and if an existing electric shower is replaced with a higher powered one (for instance a 10kW shower replacing an 8kW shower) a larger cable may be required. The size of the cable needed also depends on length and where the cable is run; it should not be run in, or under, loft insulation. Specific isolation switches are required and the circuit should be fitted with a trip which senses any leakage of electrical current to earth, either an RCD or an RCBO. The electrical rules are strict and crucial to your safety. You will need to consult an electrician who is qualified under Part P of the Building Regulations.
Electric Shower Flow Rates
With electric showers, flow rate is almost always limited by the rate at which the water can be heated. Some showers have a low setting which is hardly ever used (not many of us are looking for cool or cold showers). The setting is left on high and the temperature is controlled by reducing or increasing the amount of water passing through the shower. The shower can only heat at a set rate and the amount of hot water reduces in Winter. This is because the incoming mains cold water is much colder in Winter; it needs more heat to reach the same temperature so you slow the flow rate down to keep it in contact with the heating element for longer.
Electric Shower Running Costs
As a form of energy electricity tends to be more expensive than gas (at least in the UK). Even with gas prices increasing, electricity is generally more than twice the price of gas. This would appear to make electric showers much more expensive to run but the lower flow rate evens things out. Pumped power showers, usually heated by gas, pass much more water. The flow rate of a pumped power shower may be 2 or 3 times higher giving much better showers but may be no cheaper to run if they're used on full.
And the benefits of electric showers? They are often cheaper to install and, not having a pump, they can be much quieter than a pumped power shower. If you don't have an alternative choice of energy they're the only choice anyway. Finally, if you love cold showers you can get brilliant flow rates for almost no cost! Back to the Top
Combination boilers (often called combi boilers or combies) provide hot tap water on demand. They heat the central heating water in much the same way as regular boilers but when a hot tap is opened they switch over to providing hot tap water. With combi boilers there is generally no hot water cylinder. Some larger combination boilers store a limited amount of hot water within the boiler provide a "head-start".
Multipoint water heaters are similar to combination boilers in that they also provide instantaneous hot water. They don't, however, provide heating for the house.
Combination Boiler Shower Flow Rates
Most combination boilers now fall in the range of 28kW output to 35kW output. They can heat tap water 3-4 times faster than electric showers and much higher flow rates can be achieved, giving much more powerful showers.
Because showers run from combi boilers can have much higher flow rates, running costs can be higher than electric showers even though gas (in the UK) is much cheaper than daytime electricity. Showers run from multipoint water heaters usually cost less than electrically heated showers and the flow rates are much better.
Higher flow rate showers are, however, much more pleasurable and as the water is constantly being heated it never runs out. This can lead to much longer shower times and can be more expensive than running a bath. Back to the Top
Combination Boiler Shower Running Costs
In nearly all geographical areas in the UK mains water is at much higher pressure than low pressure water supplied from a loft tank in a house. In most areas mains pressure is around 2-3 bar though it may be much higher. Three bar is enough to push water to the top of a pipe 30 metres high (100 feet). The stored energy which generates this pressure is called potential energy.
Venturi power showers use the potential energy in mains cold water in a simple and really clever way to draw in low pressure hot water and mix it with the mains cold water. No pump is used to deliver the water to the shower head.
Venturi power showers do not heat the water. They are clever because they can deliver a high flow shower using low pressure hot water stored in a standard hot water cylinder.
Venturi Power Shower Flow Rates
It's very hard to find published flow rate figures for venturi power showers, mainly because their flow rates depend on so many variables. Hot water may need to be stored at 65°C and mains cold pressure must be adequate (but not excessive); then it seems that flow rates will vary from 10 litres per minute to maybe 20 litres per minute, depending on the installation. A major factor will be the flow rates of hot water from the storage cylinder. Low resistance check valves should be used (swing check valves) and larger pipes with fewer tight bends. Then, the higher the cold tank (which feeds the hot water cylinder) is above the shower head, the better.
Packaged pumped power showers
Separate power shower pumps
Single impeller shower pumps (can be fitted to pump either hot water or cold water or blended water)
Twin impeller shower pumps (one impeller pumps hot water, one pumps cold but both impellers operate at the same time)
Flow switches
Positive head shower pumps
Negative head shower pumps (shower pumps which can be fitted where the pump is located at or above the level of the shower head)
Venturi Shower Running Costs
With all showers, the main running cost involved is the cost of heating the water so the higher the flow rates, the more you pay. Venturi power showers can achieve high flow rates under optimum conditions and, when they do, the running costs will be higher. Remember, it depends on what fuel you use to heat the water in the first place. Daytime electric rates are high! Back to the Top
Pumped Power Shower Flow Rates
Pumped power shower flow rates vary widely. The type of shower head and shower hose make some difference but the big difference is in the power of the shower pump. These range from small, relatively cheap pumps bought from DIY outlets, to powerful pumps from specialist manufacturers.
Really powerful shower pumps are capable of emptying the loft tank of cold water faster than it can fill, so beware!
Pumped Power Shower Running Costs
The running costs of pumped power showers varies with the power of the shower pump and the amount of water the pump can deliver through the shower head. The faster the flow rates, the more expensive to run. The other variable is the cost of the fuel used to heat the water for the power shower. Back to the Top
Megaflo™ hot water cylinders
Minimum 22mm equivalent incoming cold water main is recommended
Power Shower Flow Rates from Unvented Cylinders
A power shower run from an unvented hot water cylinder can produce phenomenal flow rates many times higher than electric showers or most gravity showers. The high flow rates make it possible to run several jets at the same time (shower head and body jets), depending on the shower equipment used.
Power Shower Running Costs from Unvented Cylinders
Power showers run from unvented hot water cylinders are capable of delivering so much water that they rapidly become more expensive to run than using a bath. In the UK, gas prices are currently about one third of daytime electricity prices but unvented hot water cylinders are rarely heated by electricity. Even so, a power shower run from an unvented hot water cylinder can be expensive to run if you use its full potential!
This web site is only in the first stages of development. If you have problems with the site or you can see ways to improve it please email us. We'd to be happy to hear about simple mistakes in spelling, punctuation or layout so that we can correct them. Ideas about content for the web site are also welcome.
Albion Mainsflow™ hot water cylinders and thermal stores
Power Shower Flow Rates from Thermal Store Cylinders
Like showers from unvented hot water cylinders, a power shower run from a thermal store cylinder is capable of giving amazing flow rates and capable of running body jets as well as the shower head.
Power Shower Running Costs from Thermal Store Cylinders
Power showers run from thermal stores or from unvented hot water cylinders, showers run from combi boilers and pumped power showers all have similar running costs for similar flow rates (assuming the same fuel is used to heat the water). The faster the shower flow rate, the more it costs per minute to run.
All power showers can be expensive to run but a power shower run from a thermal store cylinders can deliver hot water so fast that it is easy to make showering more expensive than running a bath.
Environmentally too, the cost of running very high flow rate showers may become unacceptable over the next few years.
Unvented Hot Water Storage Safety Regulations
Stringent safety regulations apply to pressurized hot water storage of over 15 litres. These storage cylinders and their controls must not be modified in any way not specified by the manufacturers. See Approved Document G, G3
Besides putting together information about power showers, we're starting a new web site recording information about central heating problems and fault-finding of gas boilers and central heating controls. You can find it at www.lovekin.net
And in his spare time Paul is working on a web site about Lake Garda in Italy, particularly Limone sul Garda, Riva del Garda, Malcesine, Lazise, Bardolino and the town of Garda itself. He's hoping to earn money by carrying advertising on the site from hotels and tour operators, travel companies and other companies linked to the hotel, travel, leisure and tourism sector. The site is PictureLakeGarda.com
Multipoint water heaters are less powerful with an output of up to 24kW so the shower flow rates you can achieve are lower but they are still 2-3 times better than electric showers.
With showers run from combination boilers or multipoint water heaters however, temperature fluctuations can occur if hot water is drawn off from another point served by the appliance. This effect is limited by fitting a thermostatic shower mixing valve and this is recommended.