Mm, the difficulty is that it can be medicalised too early, when it isn't a medical problem or concern at six.
So, you can make sure they are drinking enough, but at six it isn't really necessary to intervene too much - two of mine went through the whole peeing in a jug to measure output so that professionals various could determine bladder capacity, ultrasounds on full and then emptied bladder to check for residual urine and emptying, blah, blah. Kidney scans etc etc. Quite alarming for a six yo, and certainly enough to convince them they have a medical problem. something 'wrong' with them. At six, as long as they are getting enough to drink, it's important not to view this as a medical problem.
Because it just isn't. It's entirely normal to bed wet at 6. It's also entirely normal not to. Luck of the draw. Two of mine wet way past six, and one was dry day and night at two. We did nothing differently.
Try and hold off on 'professionals' until 7, if you can. You really don't want to make your child think there is any issue with this. You can offer more drinks if you think this might be a complicating factor, but no need to suggest he needs to drink more...