Since many years Chester`s elephants are no longer chained at night, not even in the old house. And certainly not in the new house. The females and calves spend all nights together in the big indoor yards with sand floor and when the weather allows, the doors stay open so that the eles can choose whether sleeping indoors or outdoors. Plus they have lots of space for socialising, playing ect. which is important since elephants don`t sleep more then 4-6 hours each night. I think Chester was one of the first zoos in europe to realize how bad it is for elephants to lock them into small stalls during the night, or chain them which is even worse.
Some zoos (not sure about Chester) chain the elephants in the morning for an hour or so to give them a bath, footcare ect. YOu may have seen/heard that.
There is not even a SINGLE zoo left in the UK which chains the elephants overnight - the last may have been Woburn in the old house, but I am not sure about this and it is certainly no longer necessary in the new, very big house! Nowadays you have to search long and hard to find a zoo which still chains elephants overnight - in Germany, at least a dozend of zoos have stopped overnight chaining in the last years and now there are very few - maybe 5 or less!) left who still do that over here.