What's the amount of psi a 5 gallon water bottle can hold? My 5 gallon is filled with beer and a compressor is used to maintain a pressure. I do not want my bottle explodes!
I use a 5 gallon of water because I don't have a normal 5 gallon keg.
Given that these are not designed to take pressure, I'd say the maximum safe pressure is zero. Any more than that, and you're taking chances.
If that's a chance you're willing to take, then the best way to know the maximum pressure is to get several of these and pressurize to breaking point. The maximum safe pressure is then half of this breaking pressure.
I'm assuming you want to hold pressure to carbonate. Even if you do successfully carbonate without exploding the bottle, further danger comes if you knock the bottle or drop something in it that causes the CO2 to quickly come out of solution. Then you may get a quick buildup of pressure in the neck of the bottle, more than the bottle will tolerate.
You're far better off saving up for a keg, or using beer bottles, or plastic soda bottles - all of these are designed to take pressure.