earlier I peeled 4 potatoes

[RattleAndRoll]

I didn't use them in the end tonight.
Tomorrow we're not home for dinner. Will they last til Saturday for dinner for mash or something?
They're currently in a bowl of water.

[thenumberseven]

Yes, keep in a bowl of water in fridge. If keeping more than a few hours take out of bowl, wash under running water and put back in bowl with fresh water.
Repeat until ready to use. Important to keep in fridge

[RJnomore]

Why not cook and mash now, that will definitely keep until saturdaynin the fridge.

[RattleAndRoll]

Thanks both. At the mo doing as suggested - in water and keep changing it.

I've never pre-made mash. How do I reheat it? When do I add butter etc?
Does it taste just as good?

[4merlyknownasSHD]

Pre-made mash does not taste as good. Not too bad either, just not quite as good as fresh. The addition of something like chives or mustard helps.