--- title: "Why you should run the hot water before starting a cycle" description: "The first fill comes from whatever is sitting in the pipe, and a cold start makes the machine wash worse and run longer." url: "https://dishwasherrepair.center/guides/run-the-hot-water-first/" date_modified: "2026-09-25" --- Maintenance and prevention # Why you should run the hot water before starting a cycle Run hot water before starting the dishwasher so the first fill comes in hot, not cold from the pipe. Open the kitchen tap until it runs hot, shut it and start the machine straight away. Whirlpool asks for water at about 120°F entering the machine, the heater setting CPSC urges against scalds; the dishwasher's own heater raises the temperature from there. Hotter first fills mean shorter cycles and better cleaning. By [DishwasherRepair.center technical team](https://dishwasherrepair.center/authors/technical-team/) Published September 25, 2026 ## At a glance. A dishwasher draws its first fill from the hot line under the sink, and whatever is sitting in that pipe goes into the tub. On many homes that first fill is cold, and the machine spends the start of its cycle warming it up. Read the whole guide ### What to do Run the kitchen tap hot, then start Usually thirty seconds to a minute, longer where the water heater is far from the kitchen. ### Water heater setting 120°F The setting CPSC urges against scalds, and the supply temperature Whirlpool asks for. ### Why it helps The first fill does the heavy cleaning The enzymes in modern detergent, and the fats on the plates, respond to warmth from the first minute. ### Where it matters most Long pipe runs and cold months Pipes through a crawl space or garage cool the water between uses. In this guide 1. The first minutes after you press start 2. How to do it 3. Checking the temperature at the tap 4. When the tap is not the answer 5. Other habits that help the heat 6. Step by step 7. Questions ## The first minutes after you press start When you press start, the drain pump runs briefly and then the inlet valve opens. A modern machine takes in a small amount of water for each fill, often no more than a long pipe between the water heater and a far sink holds. On those homes the prewash or the main wash may start with water no warmer than the room. The dishwasher is not helpless: its heater, either an element on the tub floor or a heater built into the pump, raises the temperature. It does so slowly, and many models pause the cycle until the water reaches a set point, which is one reason a cycle can take much longer than the display first suggested. Winter makes the gap wider. Water entering the house is colder, pipes in exterior walls or crawl spaces lose more heat, and the same kitchen that gets hot water in ten seconds in August may need a minute in January. ### Sensor-held cycles A thermistor in the tub reports the water temperature to the control board. On sensor cycles the board adds heating time until the target is reached, so a cold fill quietly adds minutes and energy to every load. Owners who complain about three-hour cycles are sometimes describing a long cold pipe rather than a broken machine. Source: [Whirlpool — How water temperature affects cycle time](https://producthelp.whirlpool.com/Dishwashers/Product_Info/Dishwasher_Tips_and_Tricks/How_Water_Temperature_Affects_Cycle_Time) — Run the nearest hot tap first; the cycle pauses to heat water ## How to do it The habit takes less time than loading the silverware basket. To run hot water before starting the dishwasher properly, use the tap that shares its pipe, and do it last, after the racks are full. Its payoff is biggest on a first load of the day, when every pipe in the house has cooled. Source: [Whirlpool — How water temperature affects cycle time](https://producthelp.whirlpool.com/Dishwashers/Product_Info/Dishwasher_Tips_and_Tricks/How_Water_Temperature_Affects_Cycle_Time) — Run the nearest hot tap first; the cycle pauses to heat water A hand under a kitchen faucet feeling the water as it runs hot, steam faint, a closed dishwasher beside the sink. ## Checking the temperature at the tap You can find out whether this matters in your home with a kitchen thermometer. Run the hot tap for a minute, fill a glass and read it. CPSC urges a water heater setting of 120°F against scalds, Whirlpool aims for the same figure at the tap, and a reading close to that means the dishwasher is starting well. - Well under 110°F after a full minute: the water heater may be set low, or the pipe run is very long. - Around 120°F: a good supply for any dishwasher with its own heater. - Much higher than 125°F: a scald risk at every faucet in the house, and not needed for the dishwasher. ### Counting the seconds Time how long the tap takes to turn hot. That number is your routine: if it is fifteen seconds, the step barely matters; if it is ninety, it matters on every load. Homes with a recirculating pump on the hot line get hot water almost at once and can skip the step. ### Homes with a tankless heater An on-demand heater lights its burner or element only above a certain rate of flow. A dishwasher's small, short fills can fall below that threshold, so some of its water arrives unheated even after the tap has been run. Check the heater's minimum flow rate in its manual; a small buffer tank or a recirculation setting is the usual answer. Source: [Whirlpool — Dishwasher water temperature troubleshooting](https://producthelp.whirlpool.com/Dishwashers/Product_Info/Dishwasher_Tips_and_Tricks/Dishwasher_Water_Temperature_Troubleshooting) — Run the tap 30 to 60 seconds and aim for 120°F; [CPSC — Avoiding Tap Water Scalds](https://www.cpsc.gov/safety-education/safety-guides/kids-and-babies-home/avoiding-tap-water-scalds) — Set water heaters to 120°F to prevent tap-water scalds ## When the tap is not the answer Some complaints look like a cold-supply problem and are not. A cycle that runs long even with a hot first fill, a display that sits on the same time for half an hour, or dishes that are cold and wet at the end point to the machine's own heating rather than the plumbing. The reverse also happens. A tap that never gets properly hot, whatever you do, is a water heater question: a thermostat set low, a failing element in an electric tank, or sediment filling the bottom of an old one. The dishwasher only reveals it, because it is the appliance that most depends on the supply. - Hot tap, cold dishes and a very long cycle: have the dishwasher's heater circuit checked. - Lukewarm tap everywhere in the house: have the water heater checked first. ## Other habits that help the heat The water temperature is one part of how well a load comes clean. A few other habits work with it rather than against it. None of these replaces a working heater. They only let the machine spend its energy on washing rather than on catching up from a cold start. - Avoid running the dishwasher while someone is showering or the washing machine is on a hot fill; they compete for the same tank. - Choose the heated or high-temperature option for greasy pans and plastic storage containers that need a hot rinse to dry. - Scrape plates rather than rinsing them hot at the sink; sensors read slightly soiled water and adjust the wash accordingly. - Load so that nothing blocks the spray from the heater or the thermistor on the tub floor. ## Where to stop If the dishwasher runs for hours and dishes come out cold even though the tap is hot, the heater, its relay or the thermistor may have failed; do not open the base panel to test them, because those parts carry line voltage. Never raise the water heater thermostat far above 120°F to compensate for a machine that does not heat. Written by [DishwasherRepair.center technical team](https://dishwasherrepair.center/authors/technical-team/). The dishwasher technicians behind the service visits booked here. Each article grows out of problems met in real kitchens and is compared with the maker's manuals and service literature wherever those are published. Sources: [Whirlpool — How water temperature affects cycle time](https://producthelp.whirlpool.com/Dishwashers/Product_Info/Dishwasher_Tips_and_Tricks/How_Water_Temperature_Affects_Cycle_Time) · [Whirlpool — Dishwasher water temperature troubleshooting](https://producthelp.whirlpool.com/Dishwashers/Product_Info/Dishwasher_Tips_and_Tricks/Dishwasher_Water_Temperature_Troubleshooting) · [CPSC — Avoiding Tap Water Scalds](https://www.cpsc.gov/safety-education/safety-guides/kids-and-babies-home/avoiding-tap-water-scalds) ## Step by step. Three steps, in the order worth doing them. 01 ### Open the kitchen hot tap Use the faucet nearest the dishwasher, since it shares the same branch of pipe. 02 ### Wait for real heat Keep a hand under the stream until the water turns hot and stays hot, not just warm. 03 ### Close the tap and start at once Press start within a minute or so, before the water in the pipe cools again. For the heart of your home. ## Questions owners ask. ### Is my dishwasher connected to hot or cold water? Most US installations use the hot supply, often from a dedicated valve under the sink. If the tap test shows hot water but the machine's first fill always feels cold, the supply line may have been connected to the cold side and should be checked. ### Does running the tap waste more water than it saves? It uses a small amount, which can go into a pitcher for plants. In return the machine heats for less time and cleans better on the first cycle, which avoids running a second load. ### Do drawer and compact models need this too? Yes, and arguably more, because their fills are smaller and a given length of cold pipe makes up a larger share of the water they take in. ### Does the sanitize option depend on a hot supply? It relies on the dishwasher's own heater to push the final rinse well above tap temperature. A hot first fill helps it get there sooner, and a cold one can make the option run noticeably longer. ## The problems behind it. Each has a page of its own: what it usually means and the causes in the order worth checking. [All 17 problems](https://dishwasherrepair.center/problems/) Problem ### Dishwasher Cycle Takes Too Long 5 causes, cheapest first Problem ### Dishwasher Not Heating Water 5 causes, cheapest first Problem ### Dishwasher Not Cleaning Dishes 5 causes, cheapest first ## When it needs a technician. 23 error codes on this site send owners here first. The repairs on the right are where this guide ends when the checks do not settle it. [ASKO F41](https://dishwasherrepair.center/error-codes/asko-f41/) [Bertazzoni F8](https://dishwasherrepair.center/error-codes/bertazzoni-f8/) [Bosch E09](https://dishwasherrepair.center/error-codes/bosch-e09/) [Dacor HC](https://dishwasherrepair.center/error-codes/dacor-hc/) [Fisher & Paykel A09](https://dishwasherrepair.center/error-codes/fisher-and-paykel-a09/) [Fisher & Paykel A11](https://dishwasherrepair.center/error-codes/fisher-and-paykel-a11/) [Fisher & Paykel A60](https://dishwasherrepair.center/error-codes/fisher-and-paykel-a60/) [Fulgor Milano E3](https://dishwasherrepair.center/error-codes/fulgor-milano-e3/) [Gaggenau E:2060](https://dishwasherrepair.center/error-codes/gaggenau-e2060/) [GE C6](https://dishwasherrepair.center/error-codes/ge-c6/) ### Heating and drying repair Cold washes, wet dishes and cycles that run for hours, traced to the heater, its sensor or its safety cutout. ### Fill and water valve repair A dishwasher that will not fill, fills too little, or keeps filling, traced through the valve, the float and the supply. ### Controls and sensors Dead panels, stuck cycles and blinking lights, separated into board, keypad, sensor and wiring before a part is ordered. ## More in maintenance and prevention. The few routine jobs that head off most of the calls we get, and how often each one is really needed. [The whole section](https://dishwasherrepair.center/guides/maintenance-and-prevention/) Keeping it out of trouble ### Filter and spray arm cleaning, step by step A ten-minute routine that keeps wash water clean and every nozzle spraying, with honest intervals for different households. Keeping it out of trouble ### Hard water and rinse aid: ending spots and cloudy glasses Grains per gallon, the rinse aid dial, the hardness setting and a vinegar test that tells mineral film from permanent etching. Guides ### All 18 guides Six sections, by what you are trying to find out. --- **[Read on the site: Why you should run the hot water before starting a cycle](https://dishwasherrepair.center/guides/run-the-hot-water-first/)** **[Book a visit with DishwasherRepair.center](https://dishwasherrepair.center/schedule/)**