I&I 101: Stop Draining Your Budget

Here's an uncomfortable truth about most collection systems: you're probably paying to treat a lot of water that was never supposed to be in your pipes. That's inflow and infiltration, and for many utilities it's one of the biggest hidden line items in the budget.

Let's break down what it actually is.

Infiltration vs. inflow

They get lumped together as "I&I," but they're two different problems:

• Infiltration is groundwater seeping in through cracks, bad joints, and deteriorated pipe walls. It's a slow, steady leak that gets worse as your system ages.

• Inflow is stormwater rushing in through direct connections: things like illegal downspout connections, leaky manhole covers, and cross-connections with storm drains. It spikes hard during rain events.

One is a chronic drip. The other is a flash flood. Both end up at your treatment plant.

Why it costs you

Every gallon of clear water in your sanitary system is a gallon you're paying to convey and treat for no reason. Worse, I&I steals capacity. During a heavy storm, all that extra water can overwhelm your lines and contribute to sanitary sewer overflows, which carry real regulatory and public health consequences. In effect, I&I makes your system act smaller than it actually is.

How you find it

There's no single magic tool, but the usual toolkit includes flow monitoring (watching for flows that don't match the population), night-flow analysis, smoke testing to reveal inflow connections, and CCTV inspection to physically see infiltration points like cracked joints and failing laterals.

That last one is where condition data earns its keep. When your inspection footage is coded consistently, infiltration defects get flagged, graded, and placed on a map. Instead of knowing you have an I&I problem, you know where it is, which is the only way to fix it cost-effectively.

From symptom to source

Chasing I&I without good condition data is like bailing a boat without looking for the hole. Once you can see the cracked joints and compromised segments on a map, you can target rehabilitation where it'll actually reduce flow, rather than spreading the budget thin and hoping.

Want to turn your inspection videos into a map of where water is getting in? Schedule a demo.