Water Contamination

During a very hot summer a health inspector visited Pat's farm because he was worried about the fact that his family used water from a well for domestic uses. The conversation went thus:
Inspector: 'What precautions do you take against your water being contaminated?'
Farmer: 'We boils it. Then we filters it. We keeps it in spotless buckets.'
Inspector: 'Very good and then?'
Farmer: "Then we drinks porter.'