It's a tricky age isn't it? There are loads of problems you can canounter at this age, but as they are still learning so much, it's difficult to find a strategy that works.
Do you know for what reasons he wakes?
Break them down into possibilities and deal with them one at a time. Get the heating in the room right, with the appropariate clothing. Once you are sure this is solved then start on the other things.
I am almost certain (obviously only almost, because we can only ever comment on similar behaviour with our own) that sleeping through is something all children CAN do, and it is a question of training them to do it.
His waking seems a) habitual and b) something that's been going on for some time now?
Get your daytime structure sorted and consistent. Even if he doesn't nap always - put him in his room "for a nap" at the same time every day. I think that even at this age, daytime sleep can still balance out nightime sleep. Try and do it every day (I know this is hard, because you have to be at home etc.) D the exhausting things in the mornings, and have quieter afternoons.
Then start to deal with night wakings. Decide on a strategy, and then (hard bit) stick to it rigidly. No matter what.
Even if he wakes up completely, I think that the message has to get through eventually, that he has to go back to sleep himself. I do believe they pick up on the fact that you will come and see them if they shout loud enough. They can seem to have very "sound" reasons for your help (cup of water, dummy etc) but I think you need to stop giving him whatever he asks for, because he will just know then, that he can keep getting you up for this help.
I think (I say a lot of I think, because again - only you know your own child best) that you can always go in once. But do not talk, or make eye contact, or work in the dark / with minimal lighting. Once it's established that he is not ill / been sick, or whatever, simply say "It's bedtime now" and "time for sleeping". Tuck up and leave the room. Then either don't go back in, or do it in a CC fashion (wait 5 mins, then leave it 10 mins, then leave it 15 mins etc). TRY not to get cross, talk, shout, reason, give into demands. Sooner than you think, he should pick up on the fact that mummy (or daddy) is VERY borning at night, and there's no point in waking up at all.
I do know this. EVERY difficult nighttime sleeper (who has no other "issues" like excma / SN or whatever) I have ever come accross in r/l (or on teevee!!) can be persuaded by a consistent strategy to give up nighttime waking. But once you start emplying your strategy, you will find the first few nights hellish, and that's why it's so hard to be consistent.
Anyway - sorry for rambling. Hope you get a good nights sleep soon!