The Infrastructure System Replacement Surcharge (ISRS) is a program that increases Missouri American Water’s ability to perform water main replacement projects in St. Louis County. It is a small monthly fee paid by customers in the county that funds water main replacement projects in the county.

In the late 1990s, Missouri American Water was replacing an average of about 11 miles of aging water mains in St. Louis County each year and filing rate cases annually to recover those costs.Each rate case costs customers more than $1 million.

The industry’s suggested replacement rate for water mains is 1 percent (based on a 100-year lifespan), which means that every 100 years, all mains would be replaced.Most water systems in the country are averaging a replacement rate of 225 years, which is insufficient to cover the expected lifespan of the typical water main.In St. Louis County, the ISRS program has allowed Missouri American Water to accelerate its replacement rate among the county’s 4,200 miles of water main to 125 years. This is still short of our 100-year goal, but is a step in the right direction.

How much does ISRS add to my bill?

ISRS currently totals about $3.47 per quarter for a typical residential customer in St. Louis County.

How is the ISRS charge calculated?

The ISRS fee is calculated based on the cost of work performed by Missouri American Water that qualifies as ISRS-related (main replacement work), divided among St. Louis County customers. Work that is not related to main replacement projects is not covered by ISRS, but is instead collected via the traditional rate-setting process.

Following is a summary of the ISRS surcharges, by customer type, effective on or about December 15, 2017.


Rate per 100 gallons of water

Residential, Commercial or other Public Authority


Large Industrial


Resale Customers


ISRS is implemented pursuant to Sections 393.1000, 393.1003, 393.1006 RSMo; CSR 240-2.060 (1)and 4 CSR 240-3.650

Can’t Missouri American Water pay for main replacement without a separate fee?

American Water, the parent company of Missouri American Water, is going to invest its available capital into projects in which it can earn a timely return on its investment. Without ISRS, replacing mains in Missouri is a capital investment that is ongoing, but can only be recovered via rate cases. Because of that, the parent company generally chooses to invest its funds elsewhere, where the return comes more quickly.

Missouri American Water still replaces the oldest and most troublesome mains in our system, but at a much lower frequency than we can with ISRS. We simply don’t have the capital to replace them as quickly as needed. What this means is that many mains that are due for replacement will not be replaced in a timely fashion and as a result, main breaks will increase in frequency.

Missouri American Water has invested more than $550 million to replace 8.8 percent of its water main system in St. Louis County since ISRS began in 2003.

The company went from investing $7-$9 million a year for pipe replacement pre-ISRS to investing $50-$80 million in recent years with ISRS.

How old are our water pipes and why do they need to be replaced?

Some of the pipes in Missouri American Water’s distribution system are more than 120 years old!These pipes wear over time based on the pipe material, soil characteristics and temperatures, becoming susceptible to corrosion, leaks, and breaks. It is estimated that 2 trillion gallons of water is lost each year in the U.S. due mostly to aging, leaky pipes and water main breaks. This amounts to 14-18 percent of all treated water. In St. Louis County, about 24 percent of treated water is lost, or 50 percent more than the national average.

Replacing old pipe before it breaks again is important for several reasons:

  • Leaks and breaks are a potential source of water contamination, so we need to maintain our system to keep our customers safe.
  • It is 10 times more expensive to fix an emergency water main break than to perform ongoing upgrades.
  • Leaks waste a lot of water. As noted above, in St. Louis County, about 24 percent of treated water is lost, or 50 percent more than the national average.
  • Unlike main breaks, replacements can be scheduled to minimize disruption to schools, businesses and residents.

Do other states use ISRS?

At least 10 other states use an ISRS program.Most of these states are in the mid-west and northeast, where systems are older and in greater need of replacement (MO, IL, IN, OH, PA, NY, DE, NJ, CT, NH, CA).Most states refer to the mechanism as DSIC, or Distribution System Investment Charge.