Newb ginger beer questions

[protonoto]

I've just became interested in trying to brew some of my own ginger beer, I have tried doing a simple recipe in plastic bottles. However it seems after about 2 days the ginger becomes sour and isn't really drinkable.

I'd like to know what can be done to prevent it becoming sour, also if anyone has any better methods of brewing it. At the moment I am using sugar, ginger water and yeast. I usually have to open the bottle cap every few hours to prevent it exploding, was wondering if anyone had any tips/advice.

Thanks in advance.