Inflow and infiltration is a risk in any waste system. Yet in regions with older infrastructure, groundwater and stormwater that enter a sewer system can account for as much as 50% of flow. The cost of this disruption should not be underestimated; in 2014 the EPA reported that wastewater collection and treatment expenses ranged from $2 to $5 per thousand gallons. An annual I/I volume of 150 million gallons would cost between $300,000 and $750,000 per year to transport and treat. Given that even small amounts translate into substantial costs, where should you draw the line on I/I? How much is too much?