exsessive drinking

Hi, I have got a boar who is 18mnths old and has started drinking a lot of water, he is drinking 150ml in a day then filled up he drinks the same over night, He has dried food in morning with veg's at lunch time and there is always hay available, does anyone know how much a pig should drink?

I would expect them to get through 50ml per pig in 24 hrs. (Depending on how much water is in their diet) So yes, your pig is drinking a lot. Did he drink less before? I would be worried he has a kidney problem, although some pigs will drink loads to flush out their system if they have a urinary tract infection or bladder sludge.

.. and some finds it highly amusing to either play with the bottle and spill the water, or to just drink it.

Is the bedding right under the bottle soaked or 'normal'? If soaked, then he is just playing with the bottle... I have those too.
Does he have access to one of them saltstones or something, and if so, is it hanging near the bottle? Some animals get into a bad habit of licking the salty thing, drinking, licking, drinking, licking, drinking.. well you get the picture. You can either move the stone to the other end of the cage, or remove it completely.
Have you tried checking if he is really 'needing' the water? Exchange the bottle with a bowl.. preferably one that won't tip over easily. If he has a medical condition that forces him to excessive drinking - it won't matter if the water is in a bottle or a bowl, he will still drink lots. But if he is finding that the bottle is a fun toy, then a bowl isn't nearly as fun... and he will drink considerably less.

Is he defo drinking it rather than a leeky bottle?

The bottle is not leaking as the bedding underneath is quite dry, i will try a little dish now and see what happens, H e didnt used to drink this amount before, and no he doesn't have any salt lick's.
But going with stella's note i think it migt be kidney infection, i weighed him this morning and he has lost weight since last weighing him 2wks ago, he was 800g now he is 700g?.
any idea's before i visit the vet.

Sorry forgot to say He is quite lively and eating all food etc,

try with the bowl, just to make sure.
If he is playing 'I can drink lots of water' then it won't be fun anymore. And you can tell the vet that you tried checking if he needed it. And if it is playing, and he's filling the belly with water - then no wonder he's loosing weight, cause his stomach will feel full all the time.
I am definitely not ruling out that there is a good chance of it being kidneys or something - I just like to rule all other possibilities out as well.

Thanks i am on way to do the bowl,

Have you started feeding anything different recently?

My pigs started drinking more when I feed them dry bran...

Don't want to worry you, but it could be something else... I have suffered with damn leaky bottles and have lost 3 litres of water a day having to clean out constantly (nightmare... damn 1.1litre classic bottles!) Not had prob since replacing. HOWEVER, I very recently lost a 9 month sow to kidney failure. Heartbreaking. She only ever showed the signs by drinking lots. I knew pretty soon this was what it was. She was happy and healthy right until the end. With kidney failure they are meant to start losing weight (wasting) but she never did. I came down in the morning and she had collapsed and appeared to be very uncomfortable. I booked appointment with vet but she had gone before I got there I kept appointment anyway and she said she was full of leaked fluid from her organs and also cancer (she found internal lump). IF this proves to be the case with your boar there is no treatment so no need for a vet. In my pigs case she was perfectly happy and 'healthy' until the end, so no reason to PTS either. Because my girl lived indoors I was aware of her excessive water consumption. She lived with other sows, so had she have been outside I would never havd known she was 'sick.' I don't want to worry you though, it may just be a pesky bottle! But you should be aware incase it is this. 9 months my poor girl was and she started drinking excessively from the day I bought her She was so sweet, we miss her I hope that this is not the case for your boar. Good luck x