How long without water is reasonable?

[GnomeDePlume]

Looking for some advice please?

Water in the offices (and whole local area) was off so no water for toilets/hand washing/drinks.

How long should staff wait for information from senior managers to find out what they are supposed to do ie whether to stay or go?

What is considered reasonable in exceptional circumstances please?

An hour or so ? Depends on circumstances

Depends. You say the area is like this, so there's an external issue that the water board will be dealing with. Trying to get info from them is hard at times because the people on the phone dont have the full info, because the people dealing with it are busy rectifying the issue to give constant updates. Which would increase the time to fix.
So at the moment the managers might not know themselves what is happening, or they are being told should be sorted soon.

Water was off all night but there was no information on arrival at 8am. Most of the people who were able to do so went off to work from home.

HR are kicking off a bit saying that people shouldnt have left. Problem is that people had been in the office for a while without information. In the end people made decisions for themselves - no one was sure how cross legged they needed to get before leaving.

I dont think that this is going to turn into a disciplinary thing just really trying to work out how to play this on Monday!

Pretty sure that you have to have functioning toilets, handwashing facilities and drinking water available as standard.

You do have to have toilets and hot water at all times - but sensible approach needed if the whole area is out and it's an office. May take an hour to get info.
Depends on type of workplace too e.g a kids nursery would be higher risk due to kitchens needing water, kids needing drinks and nappies being changed etc