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Around the House · Orlando · Winter Springs · Sanford
Your Water Heater and Our Hard Aquifer Water
Hard water leaves lime and sediment in a water heater, so set it to 120°F, drain or flush it on the schedule in its manual, and never block the relief valve. Replacement in Seminole County needs a permit.
Water heaters north of Orlando work with hard water from the Floridan aquifer, and that shows up as scale and sediment over the years. One maker's manual puts it plainly: how much lime and sediment builds up depends on the hardness of your tap water. The two local suppliers that publish a hardness figure both land in the "hard" range, so a little routine care pays off.
Why does hard water matter for a water heater?
Calcium and magnesium drop out of hot water and settle in the tank or coat electric heating elements. The A. O. Smith manual says sediment forms in the bottom of the tank and lime forms on elements, and that in very hard water you should check the elements whenever you drain the tank.
How hard is the water here? OUC reports an average of about 129 mg/L, roughly 7.5 grains per gallon (OUC rounds it to 7). Winter Springs has stated 150 mg/L, about 8.8 grains per gallon (the city rounds it to 8). The USGS calls 121 to 180 mg/L "hard". Most other local suppliers don't publish a number; our hard water story explains how to ask or test.
Published hardness for local suppliers
| Supplier | Published average hardness | USGS class |
|---|---|---|
| OUC (Orlando) | About 129 mg/L, roughly 7.5 gpg (OUC says 7) | Hard |
| City of Winter Springs | 150 mg/L, about 8.8 gpg (city says 8) | Hard |
| Seminole County Utilities, Sanford, Lake Mary, Longwood, Altamonte Springs, Oviedo, Casselberry, Orange County Utilities | Not published | Ask the utility or test at home |
What temperature should the water heater be set to?
Set it to 120°F. The U.S. Department of Energy calls that a temperature considered safe for most of the population, and the Consumer Product Safety Commission urges everyone to lower their heaters to 120°F. The CPSC numbers are sobering: most adults suffer third-degree burns after 2 seconds in 150°F water, 6 seconds in 140°F water and 30 seconds in 130°F water. Even at 120°F, five minutes of exposure can do it. Young children and older adults are hurt most often.
Consumer Product Safety Commission, Publication 5098
Source: CPSC
There is one trade-off. Sanford's water FAQ notes that a rotten-egg smell can come from harmless bacteria multiplying in water heaters set below 120°F. If your hot water smells and the cold doesn't, read our rotten-egg smell story before changing anything.
How often should I drain or flush the tank?
Follow the manual for your heater. As a general energy tip, DOE suggests draining a quart from the tank every 3 months to clear sediment. A. O. Smith's own schedule for one of its electric models is to drain and flush the tank and inspect the anode rod after the first six months, then at least once a year.
Homeowner work here means shutting off the water supply, switching off the heater's breaker for an electric unit, and draining the way the maker describes. Anode rod checks and replacements go by your heater's maker; the anode protects the tank, so it should never simply be pulled out and left out. Burner, gas valve and wiring work is for a licensed pro.
What should I know about the relief valve?
Never cap, plug or block the temperature and pressure relief valve or the pipe that runs from it. The A. O. Smith manual warns that an explosion could occur if the valve or its discharge pipe is blocked. The same manual says to operate the valve once a year and have it inspected every 2 to 4 years; the water that comes out is scalding, so many owners ask their plumber to do the yearly test at a service visit. If it drips or won't reseat, call a licensed plumber rather than stopping the flow.
Do tankless water heaters handle hard water?
They need extra care. Rinnai's manual for one outdoor model says that in hard-water areas the water must be treated and/or the heat exchanger flushed regularly, that scale shows up as an "LC#" code, and that heat exchanger damage from water quality isn't covered by the warranty. That manual lists a maximum total hardness of 200 mg/L. Its flush procedure circulates 4 gallons of white vinegar for at least 1 hour; other models differ, so use your own heater's manual. Our water softeners story covers treatment choices.
How long does a water heater last?
DOE says most tank water heaters last 10 to 15 years, and tankless models can last more than 20. Water heating is about 18% of a home's energy use, which is one more reason the 120°F setting and a clean tank matter. A heater that refills itself can also hide a leak; the meter checks in our high water bill story will catch it.
Do I need a permit to replace a water heater?
In Seminole County, yes. The Building Division lists replacement of a water heater as work that requires a permit, and the county works under the Florida Building Code, 8th Edition (2023). A licensed plumber normally pulls the permit; our hiring a plumber story shows how to check one.
A. O. Smith lists a drain pan, a thermal expansion tank, a pressure-reducing valve and a leak-detection shutoff as recommended accessories. Whether the code requires any of them for your house is a question for the building department.
Readers often ask
Can I turn my water heater up to 140°F to get more hot water?
CPSC and DOE both point to 120°F. At 140°F, CPSC says most adults get third-degree burns in about 6 seconds. Ask a plumber about a larger tank or other options instead.
My relief valve pipe drips. Can I cap it until the plumber comes?
No. Never cap, plug or block it. Put a bucket under the end of the pipe if needed and call a licensed plumber.
Does a softener help my water heater?
Less hardness means less scale, which is the reason Rinnai tells hard-water owners to treat or flush. Test your water first so you know what you are treating.
How do I drain a quart without making a mess?
Follow your heater's manual; it shows where the drain valve is and what to shut off first. A garden hose to a floor drain or outside keeps the sediment off the floor, and keeps hands away from water that may be scalding.
Why does my tankless heater show an LC code?
On Rinnai units, an "LC#" code signals scale building up in the heat exchanger. The manual says to flush it to prevent damage.
Where this came from
- A. O. Smith — Residential Electric Water Heater Installation Instructions and Use & Care manual — lime and sediment, maintenance schedule, relief valve warning, recommended accessories
- U.S. Department of Energy — Energy Saver (2022) — 120°F, quart drain every 3 months, lifespans, 18% of energy use
- U.S. Consumer Product Safety Commission — Avoiding Tap Water Scalds (Pub. 5098) — 120°F advice, burn times
- Rinnai — V53e tankless installation and operation manual — hard water, LC# code, warranty, vinegar flush, 200 mg/L
- OUC — Water quality reports and FAQ — average hardness 129 ppm
- City of Winter Springs — Potable (Drinking) Water (archived 2024) — average hardness 150 mg/L
- USGS — Hardness of Water — hardness classes
- City of Sanford — Drinking Water FAQ — odor from heaters set below 120°F
- Seminole County Building Division (archived 2026) — water heater replacement permit, Florida Building Code 8th Edition