Most Brits think that they can take water for granted, especially the sort of water that falls through the air and ruins outdoor outings.  If anything, it’s fine weather that can’t be taken for granted.  But in spite of the notorious climate, we shouldn’t take our water for granted, especially the water coming through our taps.
You need good, clean water for drinking, cooking, and washing hands, clothes, dishes and bodies.  And we’re lucky to have this water coming through our taps into our homes.  You just have to read a bit about rural areas in third world countries to realise how lucky you are. Even urban centres in developing countries don’t have safe water on tap, even if they do have plumbing; rural areas would consider themselves lucky if they have a pump that works near their home.  And with all the people living in the metropolitan areas of Britain, sometimes the supply of good water can get a bit stretched. 

 
Water is essential for cleaning, as it is the closest we have to a universal solvent.  Many stains, spills and other nasties can be dealt with and cleaned away by giving the grubby item a good soaking.  Incidentally, all that many cleaning products do is to increase the “wetting power” of water so it can lift away more dirt.  Soap is the classic one, which is why soap and water do such a good job of cleaning things.

 
Hard water can be a problem in some areas, as the mineral content in the water can build up and leave deposits all over the place where you don’t want it to.  Hard water also disagrees with soap and reacts with it to make a whitish scum that can get left on places; this is limescale.  You can remove limescale with natural methods: vinegar is your best bet, as the acid reacts with the deposit and helps remove it – you will need some elbow grease as well.  You can also prevent the build up of limescale in dishwashers and washing machines (where they can really do damage) by using a magnetic water softener – these can be large or small.  

 
You don’t need to worry about drinking hard water.  The minerals in them are beneficial – calcium and magnesium – and some people pay large amounts to buy it in bottles.  Consider this a bonus, even if you’re cursing that *($%@# limescale in your teapot making the tea taste funny (fill the teapot with a strong solution of vinegar and leave overnight before scrubbing it out).

 
Once you’ve used clean water for washing, still don’t take it for granted.  Water that is only a little bit soapy (plus the odd bit of grime, hair and dirt) still has its uses, so don’t waste it by pulling the plug.  Don’t throw the baby out with the bathwater – in fact, don’t throw out the bathwater at all.  You may not want to keep a large barrel full of water and use this for flushing the toilet, even though this is an excellent use for greywater.  But you may be able to use the greywater in the garden.  Plants don’t mind mild soap too much, and soapy water makes an excellent natural aphid spray.  Take it out in buckets, siphon it out via a hose from the bath into the garden, or (if you’re serious about sustainability and conserving water) get your house plumbed with a greywater system that takes water from the kitchen, laundry and bathroom sinks (and the bath) and puts it into a tank or some other system for watering the garden.

 
As an aside regarding water and sustainability, don’t buy bottled water if you can help it.  These create a waste monster and are expensive, even if you recycle the bottles like you ought to.  Tap water is perfectly drinkable.  If you don’t like the chlorine or minerals in the water, then use the money you would have spent on oodles of bottles of water and buy a filtering system instead.  The most natural forms of water purifier work by distilling the water, which means that all the bits you don’t want in the water are left behind.