To thecarotidpulse - I hate to contradict fellow posters but Durulz is wrong. Yes in lowland areas and the more populated areas or more intensively farmed areas you wouldn't want to drink the water. That leaves a lot of the country where you can drink water. The very fact that I have reached the age of 38 and haven't had any stomach upsets or illnesses of any kind that could even possibly be attributed to drinkin water from streams and even lakes. I have drunk water from streams in England, Ireland, Scotland and Wales. From the north and south, west and east of our country without negative effects. I think to condemn the whole country is wrong. You do have to remember that Britain is densely populated but by far the majority of the population is in the centres of population indeed I am sure the southest makes up a huge percentage of our population. I live in the north west of England near the north Lancs / South cumbria border and it is not so densely populated on top of that there are areas where there isn't the intensive agriculture. Indeed even the livestock peeing and defecating in the fields isn't a problem as any water will filter throught the ground and I am quite confident that the micro-organisms in the soil have their effect. The main advice in hilly areas is to check upstream for a short distance for the usual indicators of potential illness such as dead and rotting sheep or a farm yard / building upstream (unlikely). Drink water from water courses that are freely flowing for about 50m or feet (I can't remember which but never really worry because if it is flowing above you it is ok IMHO). Also courses that are flowing into tarns or lakes not out of it as the tarn fed water can have time for pathogens to multiply enough to reach potentially harmful levels. There are many sensible preventions you can make to keep safe and still drink water directly from natural waterways.
I think Durulz could be thinking too southern. Down there the areas that it is safe to drink water straight from water courses are probably low. I very much doubt there are too many chemicals in upland watercourses in Lakes, Scottish highlands, Scottish Uplands (such as Glentrool hills), Northumberland, Brecon Beacons, Snowdownia, high parts of Exmoor and Dartmoor, high parts of Peak District, High fells of the Pennines (remote areas above farm yards and away from former mining areas), etc, etc., etc.
I am sure you wouldn't drink water from a river flowing through say Cambridge, Ontario where there are centres of population and industry but you might from say Algonquin Provincial Park (sorry done business with companies in Cambridge and areas around there so know it has industry there then google mapped for the nearest national parkk type place to provide a comparison). There is too much made of Britain being polluted. Thames is the cleanest major waterway in Europe. Certainly the main rivers of Europe flowing through cities as big as London or even smaller is as clean. Certainly in some areas at least. Still I wouldn't drink it. I doubt anyone would for hundreds of years. It has been cleaned up and now has seen the re-colonisation of some species that only survive in clean water. It is a major fishery for young fish for many species including endangered species. It really is a sucess story. There are some areas where they never got polluted in the first place.
Anyway I am here, posting this comment and as a kid we went for walks without taking any water or even any means of holding water. If we wanted a drink we used our hands and scooped the water up from streams. If the country's waterways were as polluted as made out I am sure I wouldnt have made it past the age of about 5 or even younger! Having said that there is a bug that enters thee waterways via the urine of rats. It causes Leptospriosis and Weil's Disease. This collects in stagnent pools on rivers when low and gets washed down from farms when there is a lot of rain. It is well known to canoeists and whitewater kayakers. I know at least two people who caught it while paddling and that was in farming areas albeit more remote areas. Of course they were rivers and not streams. I doubt anyone anywhere would take water from rivers unless in really wilderness areas.
If you want to come to Britain and drink our water for yourself please do just observe some common sense precautions.
