But the underground water supply are inside pipes so even if fertilizers seep from above ground to underground, they won't contaminate the water because water is shielded by metal or PVC pipes. What am I missing?
It is possible for contaminants to be backsiphoned into the potable water system through cross connections. A common example would be a watermain break causing a massive drop in pressure. This drop in pressure can cause the water in a nearby home to reverse direction. If the end of a garden hose is in a bucket of paint, that buckets contents will be siphoned into the water supply.
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But the underground water supply are inside pipes so even if fertilizers seep from above ground to underground, they won't contaminate the water because water is shielded by metal or PVC pipes. What am I missing?
Obama
It is possible for contaminants to be backsiphoned into the potable water system through cross connections. A common example would be a watermain break causing a massive drop in pressure. This drop in pressure can cause the water in a nearby home to reverse direction. If the end of a garden hose is in a bucket of paint, that buckets contents will be siphoned into the water supply.