Welcome to the forum
The amount an individual piggy drinks will vary quite widely - some barely drink anything, others lots. It’s also worth noting that they more fluid they take via their food then the less they are likely to drink from a bottle.
Generally speaking, as long as his intake is normal for him then there isn’t usually a concern. It is if there is a change from normal habits that you would definitely become concerned.
The need to drink comes before the need to eat so this means that if a piggy is eating normally (and is either gaining weight at each weekly weight check (if young) or maintaining their weight at each check (once stopped growing)) then they are drinking.
If you are worried though then we would advise you see a vet.
Equally we do advise that new piggies do have a vet check done so if you haven’t already had them seen since you got them, then do arrange an appointment and speak to them about his urine and drinking habits.
I’ve added a few guides below which can help further
All About Drinking, Bottles and Dehydration
Wiebke's Guide to Pees and Stones
https://www.theguineapigforum.co.uk/threads/weight-monitoring-and-management.171577/