1. [Home](/) 2. [Guides](/guides/) 3. [Water heaters in Dayton area homes](/guides/water-heater-guide/) 4. Why and how often to flush a water heater # Why and how often to flush a water heater Hard water leaves minerals behind every time a water heater runs. Flushing clears them out before they shorten the heater's life. ## Key takeaways - Sediment from hard water makes a tank louder, less efficient, and shorter-lived. - A yearly flush is a common starting point, and hard water can justify more. - Turn off the gas or power first, and never run an electric heater empty. - An old heater that has never been flushed is often better left to a plumber. ## Why sediment builds up in Dayton area water heaters Water across much of the Dayton area comes from groundwater and tends to be hard. It carries dissolved calcium and magnesium. When that water is heated, some of the minerals drop out and settle at the bottom of the tank as sediment and scale. Over time, that layer insulates the water from a gas burner, so the heater runs longer. It traps water that boils and pops. It overheats the tank bottom. In electric heaters, it can bury the lower element. Flushing removes loose sediment before it hardens. A [water treatment](/services/water-treatment/) system can slow the buildup in the first place. ## How often to flush Once a year is a common starting point for a tank heater. Homes with very hard water, or with a well, may benefit from flushing more often. Your heater's manual gives the maker's recommendation, and it is worth following. If you are not sure how much sediment you have, drain a few gallons into a bucket. Grit or white flakes in the bucket mean a flush is overdue. Regular flushing works best when it starts while the heater is new. A tank that has gone years without one is a different situation, covered below. ## How a tank flush works The basic steps for a tank heater: 1. **Turn off the heat.** On a gas heater, set the control to off or vacation. On an electric heater, switch off the breaker. An electric element that turns on in an empty tank burns out almost immediately. 2. **Let the water cool, or be careful.** Water in the tank stays scalding hot for hours. 3. **Close the cold water supply valve** above the heater. 4. **Attach a garden hose** to the drain valve and run it to a floor drain or outside, lower than the valve. 5. **Open a hot tap** somewhere in the house so air can enter, then open the drain valve. 6. **Once the tank drains,** open the cold supply briefly to stir up and push out remaining sediment. Repeat until the water runs clear. 7. **Close the drain valve,** open the cold supply, and leave the hot tap open until water flows steadily with no air. The tank must be full before you restore heat. 8. **Restore gas or power.** Relight a gas heater following the instructions on its label. A shorter version, draining a few gallons from a full, pressurized tank without shutting it down, can be done between full flushes. Use caution, because that water is hot. ## Descaling a tankless heater Tankless heaters build scale inside the heat exchanger instead of collecting sediment in a tank. Descaling uses a small pump to circulate a cleaning solution through the unit by way of service valves on the water lines. The inlet filter screen should be cleaned at the same time. Follow the maker's instructions closely. If the unit has no service valves, they need to be installed first, which is a plumbing job. ## When to call a plumber Have a plumber handle the job if: - the heater is older and has never been flushed, since hardened sediment can clog the valve or expose weak spots in the tank - the drain valve is plastic and stiff, or will not close fully after opening - the heater makes heavy rumbling noises even after a flush - you see rusty water, leaks, or water from the relief valve - you are not comfortable working with gas controls or electrical breakers Those symptoms are explained in [signs your water heater is wearing out](/guides/water-heater-guide/signs-water-heater-failing/). A plumber who services [water heaters](/services/water-heaters/) can flush the tank, replace a worn valve, and check the anode rod in the same visit. ## Frequently asked questions What if my water heater's drain valve will not close after flushing? Sediment caught in the valve is the usual cause. Opening and closing it a few times while flushing can clear it. If it keeps dripping, cap the outlet with a hose cap for now and have a plumber replace the valve. Can flushing an old water heater cause a leak? Flushing does not damage a healthy tank. On an old tank, though, sediment can be covering corroded spots or clogging a weak valve, and disturbing it can reveal a leak that was already forming. That is why a plumber should look at an older heater that has never been flushed. 3 min read. ### Want us to handle it? Mammoth Plumbing works in Dayton, Oakwood, Kettering, Beavercreek, Fairborn, Centerville, Washington Township, Springboro. [Get a quote](/contact/)[Call 937-815-2006](tel:+19378152006) ### More in this guide - [Water heaters in Dayton area homes](/guides/water-heater-guide/) - [Signs your water heater is wearing out](/guides/water-heater-guide/signs-water-heater-failing/) - [Tank vs. tankless water heaters: how to decide](/guides/water-heater-guide/tank-vs-tankless/) ### Related services - [Water Heater Installation](/services/water-heaters/) ### Service areas - [Dayton](/areas/dayton/) - [Oakwood](/areas/oakwood/) - [Kettering](/areas/kettering/) - [Beavercreek](/areas/beavercreek/) - [Fairborn](/areas/fairborn/) - [Centerville](/areas/centerville/) - [Washington Township](/areas/washington-township/) - [Springboro](/areas/springboro/) ### Other guides - [Drains, sewer lines and basement backups](/guides/drains-and-sewer-guide/) - [Leaks, frozen pipes and water pressure in Dayton-area homes](/guides/leaks-and-pipes-guide/) ## Call or text 937-815-2006, or send a quote request and we'll set up a free estimate. [Get a quote](/contact/) [Call 937-815-2006](tel:+19378152006) --- **Mammoth Plumbing** · Dayton, OH 45402 · 937-815-2006 · matt@mammothplumber.com [Get a quote](/contact/) · [Services](/services/) · [Guides](/guides/) · [FAQ](/faq/)