3 I & I Warnings

3 Warning Signs of Inflow & Infiltration (I&I)

Did you know? When clear water (rainwater or groundwater) leaks into the sewer system, it gets treated just like wastewater. This may sound harmless — but it can strain the system, cause backups, and drive up infrastructure costs for the community.

Here are three signs that a property or neighborhood may be experiencing I&I:

1. Sewer Pumps Running Constantly After Rain

If lift station pumps run continuously — or start/stop rapidly — after a storm, rainwater may be entering the sewer system where it shouldn’t. This adds extra stress to the system and can reduce capacity for real wastewater.

2. Backed-Up Pipes & Flooding During Storms

Signs may include:

• Manholes overflowing during heavy rain
  
• Stormwater not draining properly
  
• Basements or low areas flooding

These can point to sewer pipes being overwhelmed by stormwater entering the system.

3. Sudden Spikes in Flow at Treatment Facilities

• Big jumps in flow during rain or high groundwater periods often indicate groundwater or stormwater leaking into cracked pipes or faulty connections.

Why it matters
One cracked pipe in a recent case was leaking 8 gallons of groundwater per minute. If left untreated, that would equal:

• 4.2 million gallons per year
• $8,400–$21,000 in treatment costs

Fixing I&I issues protects our environment and our community’s budget.