"I'd be in the loo all day"

This is the objection people don't say and act on, and it deserves a straight answer, because it's true for a while.

If you go from three cups a day to six, you'll pee more, and for the first week or so you'll notice. In a meeting, on a train, at the cinema, the extra visits are a real cost, and nobody's wrong to weigh it. In Erica Perrier and colleagues' pooled analysis of 238 adults, lightening 24-hour pee colour by two shades on the standard eight-shade chart went with about a litre more fluid a day and about a litre more pee. The fluid you add comes out. There's no version where it doesn't.

Two things soften it. The first is timing. Most of the extra visits come from fluid drunk in the two or three hours before, so the pair, which puts the water at breakfast, mid-morning, lunch and mid-afternoon, produces visits during the working day, when there's a loo, and not at night. If the night is your worry, stop the pair after the evening meal, and have the last glass with dinner rather than at ten. I think that's the one adjustment most people need and the one they don't make, and it's why they give up.

The second is that the body adjusts, a little. I'm giving you my observation here and not a finding. People who move from a dry day to a paired one usually report that the frequency in the first week is the worst it gets and that it settles somewhat, though not to where it was, because it can't. The visits in week three are more than in the dry days and fewer than in week one.

The honest objection is that some people have jobs where a visit to the loo isn't easy, teachers, drivers, people on tills, and for them the timing matters more than for someone at a desk. For those jobs the pair moves to the breaks that exist, and the working stretch stays as it is. A glass at each break is still more than nothing after eleven.

What I'd ask is that you weigh the visits against the headache. Both are costs. One of them is a minute in a room with a door. The other is the afternoon.