Indianapolis hard water is very hard. Citizens Energy Group reports an average of 317 parts per million, about 19 grains per gallon, for its Indianapolis system, well into the U.S. Geological Survey’s “very hard” range. That hardness leaves scale in water heaters, valves, aerators and showerheads. For copper and PEX pipe it is mostly a fixture and appliance problem; in old galvanized it adds to the corrosion already narrowing the pipe.
Circle City Repipe offers repiping and pipe repair across Indianapolis and nearby communities, carried out by licensed and insured contractors. Water chemistry matters to a repipe because it bears on material choice, on what the old pipe looks like inside and on whether to plan for a softener. This guide uses the utilities’ own published figures. The whole-house repiping page covers the work.
How hard the water is, by utility
Hardness depends on the utility and, within a large system, on which treatment plant serves the address. Citizens’ Indianapolis system draws on the White River and Fall Creek surface plants and six groundwater plants, and its hardness at a given address varies with the plant serving it.
| Utility | Average hardness | Range or note | Source |
|---|---|---|---|
| Citizens Water, Indianapolis | 317 ppm, about 19 grains per gallon | 148 to 460 ppm, about 8.7 to 27 grains | Citizens Energy Group water quality |
| Citizens Water, Westfield | 360 ppm, about 22 grains per gallon | 270 to 470 ppm, about 16 to 29 grains; groundwater plus purchased Indianapolis water | Citizens water quality report |
| Carmel Water Department | Softened at the plant to about 8 grains, which Carmel calls moderately hard | Reported tap range is wide; softening may be reduced in extreme summer demand | Carmel water quality report |
| City of Lawrence Utilities | 20 grains per gallon, as last stated | Groundwater from nine wells; recent reports do not restate hardness | Lawrence consumer confidence report |
| Speedway Water Works | Not stated in its report | Wells plus surface water from Big Eagle Creek | Speedway’s annual water quality report |
| Greenwood, Noblesville and other suburbs | Check the utility’s own report | Not verified here | Each utility’s annual water quality report |
For scale, the U.S. Geological Survey classes water above 180 mg/L as very hard; parts per million and milligrams per liter are the same thing for this purpose. Citizens’ Indianapolis average is well past that line, and its Westfield system is harder still. Homeowners describe Indy water as hard all over town, and the utility numbers back them up.
What hardness does inside a house
Hardness is dissolved calcium and magnesium. It stays in solution in cold water and comes out as scale when water is heated or evaporates. So the damage concentrates on the hot side and at the ends of the system:
- Water heaters. Scale settles in the bottom of a tank water heater and coats the elements of an electric one. A tankless heater’s heat exchanger is more sensitive still, which is why makers call for regular descaling in hard water.
- Valves and fixtures. Shower mixing valves, faucet cartridges, toilet fill valves and aerators collect scale and start to stick, drip or lose flow.
- Appliances. Dishwashers and washing machines build scale in their valves and heaters.
- Pressure and expansion parts. A pressure-reducing valve or the expansion tank at the water heater can foul and stop regulating properly.
Inside copper and PEX supply pipe at normal temperatures, hardness builds up slowly if at all. Galvanized is different. Its zinc coating wears away and the steel underneath rusts, growing lumps inside the pipe, and hard water adds mineral to those lumps. Together they narrow the pipe until upstairs fixtures lose flow. One homeowner in a renovated Fountain Square house reported that same pairing of weak pressure and mineral deposits, and the plumber pointed to half-inch pipe near the main, which is a restriction problem rather than a hardness one. The low water pressure page explains how restriction is told apart from supply pressure, and the brown water guide covers the rust side.
Water chemistry and pipe life
Hardness is only one part of water chemistry, and it is not the part that usually decides how long pipe lasts. Corrosion depends on pH, alkalinity, chloride, dissolved oxygen and the disinfectant, working together. Low-pH, low-alkalinity water can attack copper and galvanized; hard, alkaline water tends to lay down a protective mineral film instead. That is why utilities treat for corrosion control rather than leaving it to chance.
Citizens’ own figures for its Indianapolis system show how that is managed. The pH averages 7.7. Citizens adds orthophosphate, averaging 1.94 ppm, which it describes as an additive to prevent lead and copper leaching from plumbing. The disinfectant is chloramine, averaging about 2.0 ppm total chlorine, and chloride averages 72 ppm. In Citizens’ tap sampling, the 90th percentile for copper was 0.097 ppm, with none of the 106 sites above the action level, and the 90th percentile for lead was 4.7 ppb, with 2 of 106 sites above 15 ppb.
Those are system figures, not a diagnosis. They do not show that Indianapolis water is aggressive, and they cannot explain a pinhole in one house’s copper. Pinholes have several possible causes, including water velocity, workmanship, stray current and local chemistry, and the copper pinhole leaks guide goes through them.
Scale, rust or something else?
A first visit checks the pipe, the pressure and the flow at fixtures upstairs and down before anyone names a cause.
Copper, PEX and hard water
Neither material is the answer to hard water on its own. Indiana’s plumbing code allows both inside the house, and the house usually decides which fits better. A few points do touch on water:
- Copper in hard, alkaline water usually develops a stable film inside. Hardness is not a reason to avoid it.
- PEX does not corrode. Because Citizens disinfects with chloramine, it is worth choosing tubing whose chlorine resistance rating suits continuous hot water use, which is marked on listed products.
- Fittings and valves are where scale sticks in either system, so accessible shutoffs matter more than material.
The PEX vs copper guide covers the full comparison, and the is PEX safe guide covers drinking water standards for plastic pipe.
Planning a softener during a repipe
A water softener is water treatment rather than piping, but a repipe is the easiest time to prepare for one. While the main is being replaced, a softener loop can be left at the point where the main enters, with a bypass valve so the softener can be serviced without shutting the house off. It is also the moment to decide what stays unsoftened: many owners keep the kitchen cold tap and outside hose bibbs on hard water, which takes a separate line.
Softened water raises sodium slightly and does not remove the need for corrosion control. A softener also does nothing for galvanized pipe that is already narrowed; only replacing that pipe restores the flow. If the old pipe is galvanized, galvanized pipe replacement is the job to look at first.
To see what your water has done to your pipe, call Circle City Repipe to set up a first visit, or read the complete guide to repiping for the wider picture.