[smsm42]

That should be not so hard to check - some companies bottle water both in plastic and glass, levels can be compared. Others use specific sorts of plastics, so one could check if the particles in their water match the chemical composition of bottle plastic or contain other plastics that are not part of the bottle. Also, many companies supply water coolers which use big bottles made of different kind of plastics than retail water - but likely the water itself, from the same company, comes from the same manufacturing process. The profile of these can be compared and one can see if the bottles are the likely source.