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Water Usage and Waste

Water Usage, Waste and Water Pump Size

How much water do we use and how much do we waste for everyday needs such as showering, toilets, cleaning teeth, cooking, drinking, washing dishes and clothes, washing the car and watering the garden? Water shortages are getting more serious across the world, how much water will we need, how much can we save and how large should our water pumps be?

A Looming World Water Shortage

saving water

In spite of havy rains and storm all over the globe shortage is becoming a worldwide problem. The UN estimates that by 2025 75% of the world's population will not have access to safe water.

The situation is rapidly deteriorating due, of course, to two reasons.

Firstly the increasing world population, 5.3 billion in 1990 and projected to be 8.3 billion by 2025 (perhaps we should cancel 2025, it doesn't sound like it's going to be a good year does it?). We appear to be breeding ourselves to oblivion don't we?

Secondly people are becoming more affluent and wasteful. Back in the 17th century British people used 2 to 3 bull's scrotums of water a day (that's the equivalent of 10 to 20 litres). These days they use about 155 litres per person per day. In Europe people use 200 to 300 litres per day while in developing countries the figure is 5 to 50 litres per person per day.

Of course much of the increase in water usage is due to the ready access to water running from taps in our houses and is used for those ever so essential items in our modern lifestyle such as washing the car, topping up the pool and giving the pooch a ginseng and ass's milk shampoo (doggy wellness is very important you know). Sadly we tend to waste much of the water we consume, straight down the plug 'ole and off to the sea bypassing that very essential water table.

Water Shortage in Bali

In Bali the predicted water crisis is starting to bite and 12 of the island's major rivers have dried up. PDAM, the water supply company, have released figures stating that the normal average water usage has reached 158 litres of clean water per person per day. This is a lot of water. PDAM does not have enough capacity being able to deliver 1,100 litres per second while demand has reached 1,200 litres per second resulting in significant pressure drops during peak usage periods in the morning and afternoon. PDAM have 5,000 people on their waiting list for water supply.

The Balinese provincial government has recently announced that they will increase the charge for water drawn from wells and bore by 1,000%, yes you heard that right 1,000%. The reason is simple, our groundwater tables are falling and salinity caused by the ingress of seawater is now said to be reaching 5 kilometres inland in some places. Soon our wells will be too polluted to use and drastic action is needed. The majority of hotels on the island are using groundwater from their own wells and bores.

How big a water pump do you need?

Last week we started looking at water pumps. There are 2 essential questions when deciding the size of pump you need, first the quantity of water you will need to pump and secondly the pressure of water you need.

We will look at water pressure another time but perhaps this is a good time to have a look at just how much water we use and this will help us to 'size' our pump.

How much water do we use each day and how to save it?

The following table provides a list of expected water usage items in everyday life. Yes it is based on averages that may or may not be accurate for you. It anticipates a water flow of 8 litres per minute through a normal water tap but this will vary of course. On the website at: you will find a water usage calculator that may help you.

Expected Water Usage



in mins
per occasion
Alternative Volume
per occasion
Brush teeth
water running
8 2 16 Brush teeth
water not running
water running
8 2 16 Shave
water not running
Flush toilet
standard toilet
    6 Fush toilet
dual flush
high pressure or
rain head
8 10 80 Shower
efficient head
Bath 8 10 80    
Wash dishes
    25 Wash dishes
by hand
Wash clothes
old washing machine
    100 Wash clothes
efficient washer
Wash car
with hose
8 20 160 Wash car
with bucket
Water garden
sprinklers and 2 taps
16 60 960 Water garden
with handheld hose
Top up swimming pool 8 120 960    
Running toilet 1 1,440 1,440 litres
per day
Dripping tap
1 drip per second
    50 litres
per week

It can immediately be seen from the table that there are easy ways of saving water.

Note there are some items that really do use a lot of water particularly watering the garden and topping up the swimming pool. Also note how much water a running toilet can use.

If you are really serious about saving water you can always head for the riverbank and a couple of big rocks to wash your clothes.

Flow rate and how to size a water pump

When sizing a water pump we need to consider the maximum flow of water we will need at any one time.

If there are 4 adults in your household you will probably be using around 600 litres per day.

If you don't have a water storage tank (and surprisingly an increasing number of people don't these days) then the pump will probably be pumping straight from the bore to your taps. The busiest time may well be in the morning.

  • We might have as many as 4 people trying to shower at the same time - 32 litres per minute
  • We've got 2 taps watering the garden - 16 litres per minute.
  • 2 toilets are refilling - 6 litres per minute
  • 1 hose is topping up the pool - 8 litres per minute
  • We'll ask James to wash the car later.

The maximum flow we need from our pump is 62 litres per minute

A tank and several small pumps can improve efficiency

Now if you use a water tank you can use a much smaller well or bore pump which will be considerably cheaper to buy and will be a much lighter load your electricity circuits.

If you have a 1,000 litre tank you will need to pump 600 litres over the course of the day and you can use a small pump for your well or bore and let it run for a long time.

In many cases people who have a large house with several bathrooms think they need a single large pump to deliver the water from the tank to the taps and showers. This has a distinct disadvantage that at times when only one shower is running the pump is too large, it switches on and off continuously and you can get problems of "pulsing" in the supply.

I suggest that it is better to use several smaller pumps to deliver the water from the tank. Better still have a tank up on a tank stand or your roof where gravity can feed the water. A nice constant pressure, no pump needed, cheaper to install and no electricity consumption.

Copyright © Phil Wilson September 2010
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