That makes perfect sense if you are under the care of urinary system specialists, and I quoted 1.2 litres for individuals with normal physiology. I’m not suggesting your physiology isn’t normal, if course, but your consultants are better informed about your particulars than I. 
Without boring the socks off everyone, a large adult in high summer can lose a large amount of water by transpiration and sweating, so extra input is necessary to keep urinary output at a level to wash out metabolites from the bloodstream, and to maintain sweating as a core temperature control mechanism.
And 1.5 litres is more realistic than the 3 litres often cited as “essential”, Graham.
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Thanks Peter. I have complete faith in my medical team practitioners 
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So…
The normal physiological need for fluid for someone without a fever is classically said to be 42ml per kg of body weight per 24 hours in a temperate environment - about 3l for an average 70kg individual.
As Peter quite rightly says it doesn’t matter what form this fluid takes, the water content of food counts towards the total and we even get a little from metabolising food - for carbohydrate approx 6ml of water is produced for each 10g of carbohydrate.
So, if you are a 50kg woman you don’t need 3l of water per day - requirements also vary by age, ambient temperature and effort. Sweating can get through a lot of water as we are able to produce a maximal volume of 3-4l per hour so if the environment is warm and/or you are working hard requirements can shoot up quickly.
Increased body temperature due to illness ups the need for water as well - again the classic figure is 2.5ml per °C of fever per 24 hours.
Symptoms of dehydration such as thirst appear at 1% dehydration (just 700mls for a 70kg adult) Difficulty concentrating, headache, and sleepiness are observed at 5%. Tingling and numbness of extremities can be seen at 6%, and collapse can occur at around 7% dehydration. A 10% loss of body water through dehydration is life-threatening.
More than you ever wanted to know here → http://www.who.int/water_sanitation_health/dwq/nutrientschap3.pdf
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Fascinating info Paul.
Had no idea my headache was possibly due to 5% dehydration.
All in all - I think I’ll stick with my habit of having a “standby” supply with me, just in case I need it.
I think you’d really notice 5% dehydration - a deficit of about 3.5l - so probably not the cause of most “ordinary” headaches 
Paul… I don’t get headaches such as most would describe - as I have said, I get a niggle front left of forehead/side temple - only when I have not drunk anything for several hours.
These days, it probably only happens a couple of times a year and if I catch it quick enough (swigging from my trusty bottle) - the niggle goes away -
If we are out in the car - I try to have a gentle swig every hour - it’s a good habit. in fact we have got into the habit of breaking any journey every couple of hours at the most, so one way or another we get respite and a drink.
John, it was always the good advice with water softeners, to leave a drinking water tap un softened for exactly the reasons you mentioned.
Thanks Stella, damb automatic correct ion
Impossible! I have a large G&T on the go.
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I’ve just worked out how many (half-pint) mugs of tea my bodyweight demands - now I’ll figure out how many glasses of wine would do the same job - hic 
You’re right stella - bloody reformed drinkers 
But hey, with a name like stella…
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Sadly I have never tried the beverage which bears my name… although I am sure it must be magnificent ! 
Sorry, Stella, it’s the very worst kind of corporate catspiss. 
. Edit: that’s just a personal opinion, I’m sure no tomcats were involved in its production, but many could disagree.
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I’ll happily cock a leg to that! 
Ian and John, thanks for you responses. Both softened and hard water is piped to a distribution point in the garage which has more pipes and levers than the engine room of the Titanic. You could well be right and the kitchen sink cold tap is unsoftened. The feed to the icemaker in the fridge too perhaps. I’ll have to trace them and see. The builder that renovated this place back in 2004 was conscientious so I’d expect him to have done the right thing. I wonder how many unnecessary bottles of water I may have dragged here over the years
