Hard Water in Phoenix Homes: Scale, Softeners and Fixtures

How hard is the water where you live?

Hardness is mostly dissolved calcium and magnesium picked up as water moves through soil and rock before it reaches a treatment plant. Phoenix draws almost all of its supply from the Salt, Verde and Colorado rivers, with a small share from City wells, and its annual water quality report puts total hardness at 172 to 302 ppm. Labs and softener makers usually quote the same thing in grains per gallon (gpg), where one grain is about 17 ppm.

North Dakota State University Extension groups water this way: below 1 gpg is soft, 1 to 3.5 slightly hard, 3.5 to 7 moderately hard, 7 to 10.5 hard, and anything above 10.5 very hard. It also notes that most people start to notice problems somewhere above 6 or 7 gpg. By that scale most metro Phoenix taps sit in the hard to very hard range.

The spread inside a single city is real. Blends of river water and well water change by zone and by season, so the number on your own utility's report is a better guide than a metro average. If you live in Mesa or Sun City, look up the zone or system name printed on your bill.

Is hard water a health problem?

No. Phoenix Water Services says hardness, taste and odor are not regulated under drinking water health standards, and that its water meets or surpasses those standards. The City's position is that a softener or filter is generally not necessary unless a doctor recommends one or you simply prefer it. Treat a softener as a decision about plumbing and appliances, not about safety.

Where scale does the damage

Tank water heaters

When water is heated, calcium carbonate drops out of solution. In a tank heater it settles on the bottom as a layer of grit and flakes. On a gas unit that layer sits between the burner and the water, and you may hear popping or rumbling as water trapped under it boils. On an electric unit the lower element can crust over and fail early. Energy Trust of Oregon's maintenance guidance says plumbers recommend draining and flushing a tank at least once a year, and sooner if it is already making those noises. If a heater is noisy, short on hot water, or slow to recover, a water heater repair visit can tell you whether a flush will help or the tank is near the end. Our guide on whether to repair or replace an aging heater walks through that call.

Tankless units

A tankless heater pushes water through narrow passages in a heat exchanger, so scale narrows the path and flow drops. Writing for Green Building Advisor, Martin Holladay describes the standard advice as descaling once a year and notes his own unit's flow had dropped noticeably after seven years without it. In water as hard as most of the Valley, annual descaling is a reasonable plan. If you are still choosing equipment, factor that chore into the tank versus tankless comparison, and a plumber who services tankless water heaters in Phoenix can set up isolation valves so flushing is a short job.

Faucets, showers and toilets

White crust on aerators and shower heads is the visible part. Inside, scale builds on cartridges and valve seats, so handles get stiff and faucets begin to drip even when shut. Pressure-balancing and thermostatic shower valves are especially sensitive because their small moving parts can stick. Fill valves and flappers in toilets wear the same way, which can leave a tank running quietly for weeks. When a shower temperature drifts or a handle will not turn smoothly, shower valve work often means replacing a cartridge rather than the whole valve.

What a water softener actually does

A conventional softener uses ion exchange. Water passes through a tank of resin beads; calcium and magnesium cling to the beads and sodium is released in their place. When the resin is loaded, the unit regenerates by flushing itself with salt brine from a second tank, then rinses that brine down a drain. NDSU Extension lists retail prices of roughly $400 to $2,700 for softeners, with salt around $5 to $10 per 40-pound bag.

A few points that matter in practice:

• Sodium. NDSU estimates about 8 mg/L of sodium is added for every grain of hardness removed. At 15 gpg that is roughly 120 mg/L. Potassium chloride can replace salt but costs more and works a little less efficiently.
• A drinking tap. Many households leave one kitchen tap on unsoftened water for drinking and cooking, or add a small filter there.
• Landscape water. Softened water is not recommended for lawns, gardens or house plants because of the sodium, so hose bibs and irrigation should stay on the hard side of the system.
• Evaporative coolers. NDSU also advises against softened water in evaporative coolers, which matters in older Phoenix houses that still run them.
• Upkeep. Keep the salt stocked, check the brine tank and float now and then, and follow the maker's schedule. The City's own advice is simply to follow manufacturer maintenance instructions.

Sizing is based on how many grains the unit can remove before it regenerates, which depends on your hardness and daily water use. A plumber who handles water softener installation in Phoenix can size the unit, put in a loop so outdoor lines bypass it, and route the regeneration discharge to an approved drain.

Salt-free conditioners and other options

Salt-free "conditioners" are sold widely in the Valley. They are meant to change how minerals form scale rather than remove them, so a test strip will still read hard after one is installed. Results are mixed, and this guide does not have a reliable public source to quote on how well they work in Phoenix water. If you are considering one, ask the seller what independent certification it carries and what the warranty covers if scale keeps forming. Reverse osmosis under the sink is a separate tool: it filters drinking water at one tap and does nothing for the water heater.

Is a softener worth it in your house?

It tends to pay off when several of these are true:

• Your utility lists hardness well above 10 gpg.
• You have a tankless heater, or a tank heater you would like to keep past its usual life.
• Fixture cartridges, toilet fill valves and shower valves have needed replacing every few years.
• You are spending real time scrubbing glass, tile and dishes.

It makes less sense in a rental you will leave soon, in a home with very little plumbing, or where your provider's number is near the lower end of the range. Some Chandler softener installs, for example, are in neighborhoods with very different hardness from others across town.

Low-cost habits that slow scale down

1. Soak aerators and shower heads in white vinegar for an hour or two, then rinse. Do this every few months.
2. Flush a tank heater once a year, or have it done. Turn off the gas or power first and let the tank cool before you open the drain.
3. Keep the water heater at a moderate setting. Scale forms faster at higher temperatures.
4. Replace a dripping cartridge early instead of cranking the handle tighter, which can damage the seat. A plumber who does faucet repair can match the cartridge to the brand.
5. If water pressure has faded over the years, scale in old galvanized pipe or clogged aerators may be the reason; see our low water pressure guide for how to narrow it down.

Hard water is part of living in the Valley. The goal is not to make it soft at any cost, but to keep scale from quietly shortening the life of the equipment you paid for.