Hello Angela
I have my little routine for weigh in days, because I think that as long as you do the same thing each week then the weight loss between weeks will be accurate.
For me, I have 1 pack at around 11am, and drink 4 litres of water up to 4pm. I have nothing then until weigh-in. I get weighed at 6.30pm, and have my other 2 packs and 2 - 3 more litres of water after weigh-in.
At my evening weigh-ins I am generally 2 or 3 pounds heavier than I am at home in the mornings before I've drunk anything, so the water really has an effect. But as long as the effect is constant each week, then my 'lost pounds' should be accurate.