Following the advice of most nappy providers we always pre-wash our nappies, new or pre-loved, before wearing for the first time.
We do this for two reasons:
To remove any residue from manufacture
To help the fibres reach full absorbency capacity
Different fibres need different amounts of pre-washes to reach full absorbency. Generally we find microfibre only needs 2-3 pre-washes, whereas natural fibres such as cotton, hemp or bamboo require 8-10 pre-washes in order to reach their maximum capacity.
Most advice states that there is no need for your nappies to dry between each wash and they can be washed at 30° so could go in with your regular loads as well as nappy loads.
I am too impatient to get a new nappy on the bum to wait for all of the pre-washes, so will use it after around two pre-washes but have to remember that they will have lower absorbency levels so change them sooner than I normally would.
Usually for pre-loved nappies I will just wash them once with my usual load (unless they haven’t actually been used). Some people advise to strip was pre-loved nappies but I guess you can use your judgement with this, if they smell I would, otherwise I feel a 60° wash is sufficient.
Recently, I learnt a very handy hack for inserts, boosters and shaped nappies, when soaked for 24 hours first, they only need pre-washing once to reach full absorbency. Although I wouldn’t do this with All-in-One nappies because I’ve heard that soaking can damage the PUL.
As wraps don’t have any absorbent elements and are covering a shaped nappy we don’t pre-wash these at all and will use them straight away.