Water with a bit of bite

On one of our terraces is a tank we collect the overflow - if we are thus blessed - from a small citerne - to water things. Today the tank had caught this wee beastie which eventually I released using a very long pole.  Not an expert on things herpetological but I think this is probably an Asp Viper, whose bite fortuitously is only fatal 4% of the time if untreated. Remind me to visit a doctor if I get bitten. If anyone knows any different, I'd be interested to hear.
DS#2 eventually arrived at about 10 pm and so it was a late barbecue for him and his seven mates.