Environmental Engineering Reference
In-Depth Information
is roughly proportional to time. Advice, from industry, government and NGO
sources, used to recommend 5 min under the shower as enough, and now there is
more talk of reducing from fi ve to four. In recent years, 4-min hourglass shower
timers have been available. See, for example, Save Water Save Money (
undated
)
and Welsh Water (
undated
).
My own conclusions on showering duration are:
Many people do indeed spend longer than the environmentally recommended
amount of time under the shower, but this is hardly surprising in view of the great
mismatch between our culture and what would be sustainable. According to
Welsh Water (
undated
), 'In Wales most people spend around 10 minutes in the
shower every day'.
Many people with a 'hectic lifestyle' rush into and out of the shower, and indeed
get from bed to work, very quickly.
The time for showering can vary greatly. A thorough wash, including proper foot
care and washing of long hair, might need 10 min (or less with a fast water fl ow).
A quick rinse, with hair protected by a shower cap and minimal foot care and
little or no soap, needs only a minute or two but is still effective if alternated with
more thorough washes.
A cold gentle shower in hot weather is wonderfully refreshing and makes all the
difference between enjoying and suffering the heat. It takes only a minute and
uses no energy and only a few litres of water. It is a continual astonishment to me
that so many people suffer real discomfort and even threat to health in hot
weather, but when this remedy is suggested, they cannot even engage with the
idea. In very hot and humid weather, several such quick cool-offs are effective
and still use little water.
Mixer Shower with Combi Boiler
This is a common type in modern use as it
combines the advantages of using cheaper fuel than electricity with the ability to
offer a high fl ow rate. If it is a power shower, that is, it pumps the water through the
rose, the fl ow rate can be higher again, up to 20 l/min or even more for multi-spray
showers. Like other designs, the products available are subject to formal and infor-
mal industry norms. The industry claims that its norms refl ect what the public wants,
which is surely true, but omits to say that what the public wants is in part created by
advertising aimed at creating new markets. The disadvantage of this design, or at
least of the existing industry norms, from a serious sustainability point of view, is
that 6 l/min is generally considered a minimum fl ow rate, although some equipment,
including fl ow limiters, do specify a somewhat lower minimum fl ow rate.
Minimum Hot Water Flow Rate of Combi Boiler and Implication for
Shower
The gas combi boiler I use cuts out if the fl ow at the kitchen hot tap is less
than 1.3 l/min and is defi nitely above the cut-in/cut-out point with a fl ow rate of
1.7 l/min. The shower needs a greater fl ow, because the shower mixes cold and hot
water to achieve the desired comfortable and safe showering temperature. This fl ow
is greater in summer, when the cold water is less cold. For an approximation to the
temperature of the hot supply to the mixer, I assume a temperature equal to that of
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