I thought you had stopped taking the Forxaga (spelling)?
That is far too much water. It will put a strain on your kidneys. It isn't a good idea to glug it down quickly. Small sips, little and often. Too much water is very dangerous. Have a Google about it. I suggest you aren't thirsty, just have a dry mouth or similar. In this heat you need extra salt.
I drank a 2 litre bottle of water working at the block yesterday afternoon, the temp was around 26° celcius, so a warm winters day. Sweating a fair bit as well so needed the drink over a period of time,
I would also have had 3 x 600 ml bottles at home over a period of time yesterday as well, although there is still a half bottle by my bedside.