ozoneted water taste is sour

Hi Folks this is my first time to post so please be patiant wih me.
I have a $60 e.bay generator. known as New 600mg Ozone Generator Water Air Sterilizer Ozonizer
and a 10g/hour double air cooled ceramic generator as follows:

w.dgozoneltdcom/PdShow.asp?ID=180

Ambient air is used on both:
when i ozoneate water i can certainly smell ozone from both, however, after ozonating for about 15-20 minutes i get a sour lemony taste. rather like an oxygen product called Cell Food. the ppm goes up to about 500. particularly on the 10/h machine. it is quite acidic. can someone please let me know if they experience the same or what is happening. Is htis normal? bad? Thankyou. NiRob