I would have thought that pure water flushes out the system but any additives (lemon, lime and so on) still make the kidneys have to do extra work and thus defeat the object.
6 pints equates to 3.3 litres approx. which seems you may be drinking too much water. The British Dietetic Association says that a guideline amount is approx. 2.5 litres per day depending on weight, height, etc. Here is a link http://www.blurtit.com/q910753.html
These cordials do have a lot of sugar in them but I can't stand the taste of tap water so I have lemon in mine ...but a fresh lemon ..squeezed . That won't do any harm and is good for you. Or I sometimes add just a dash of Robinsons orange Barley water to take the metallic taste of our water away.I drink about three pints of water like this a day and added to that several cups of black tea with lemon.
Quite adequate for me for my fluid intake.
Six pints sounds like a lot but then look at the amount of pints of beer some people can quaff in one sitting !
I would also say that just water is better purely from a dental perspective. Six pints of cordial a day means a lot of acid attacks for your nashers to cope with!!
six pints a day is far to much you will spend most of the day in the loo. every thing you eat & drink gives you liquid so adding six pints to that will do you no good what so ever. your body will tell you when you need to drink so drink when your thirsty. this six pint lark is put about by miner water companies to sell their over priced rubbish water