Dry through the night, when?

[TyMinisterForMagic]

Ds is potty trained except for the odd accident, he tends to wet himself when he has trousers on at home, only at home never anywhere else [hhmm]
How do I know when he is ready to go through the night? Any tips or advice would be welcomed please.

I started to potty train my lo 7 weeks ago and 5 days after being in pants he was waking up every morning with a dry nappy so bought a waterproof sheet for his bed and put him in pants for bed never had an accident

I waited till my lo's had dry night nappies before stopping using them. DD had just turned 3 and ds was 2 1/2 when they were dry at night.

Thanks for the replies, ds turned 3 last month, he still has very wet nappies but he drinks alot after 6pm, so was thinking of cutting drinks out after 6pm and seeing how it went, but was worried he was too young. Thanks i will give it a go tomorrow as he is with inlaws atm and they wont know the new rules :)