The Brand New Spring Hill Water Heater That Ran Out of Hot Water in Twenty Five Minutes, and the Math That Explained It

On the last day of December we installed a new fifty gallon electric water heater in a home off Fairmont Drive in Spring Hill. Within a week the homeowners called back. They were getting hot water for about fifteen minutes, and the shower pressure seemed weak. A brand new tank running out that fast sounds like a defective unit, so our plumber went back and tested it. Both heating elements read 12.4 ohms, exactly where they should be. Both thermostats switched on and passed 240 volts when tested. Nothing on that water heater was broken.

So our plumber ran the master shower on full hot and timed it. The hot water lasted about twenty five minutes. The shower had two heads, a handheld wand rated at 2.5 gallons a minute and a rain head with no marking, and the homeowners used both at once. The wand alone, at 2.5 gallons a minute for twenty five minutes, is sixty two and a half gallons. They were emptying the tank, and that was the entire answer. The weak pressure turned out to be a small filter screen inside the shower head, which our plumber removed with their permission.

That visit is worth describing because it is the honest version of a call we take all year. When the mornings cool down, people take longer, hotter showers. At the same time the water entering the tank can be cooler, so the shower valve blends in more hot water to reach the same temperature, and the heater needs more time to recover afterward. A tank that kept up comfortably in August can start running short in December without a single part failing. Pasco County Utilities buys most of its water wholesale from Tampa Bay Water, which blends groundwater with river water and desalinated seawater, and river water cools off in winter. Hernando County pumps its water from wells, where the temperature holds steadier, so in Spring Hill the longer showers usually matter more than the water temperature.

The timing of the failure tells you most of what you need to know. An electric tank has two elements. The upper one heats the top of the tank first, and the lower one heats the rest. If you get three to five minutes of hot water and then it turns cold quickly, the lower element or its thermostat has usually failed, and only the top portion of the tank is being heated. That is what we found off Sun Point Court in New Port Richey in September of last year, where the upper element read 12.4 ohms and the lower one read 2.1. If the hot water fades gradually after a long stretch, the tank is probably working and simply being outrun. If there is no hot water at all, check the breaker first. The red reset button sits behind the upper access panel, and that panel should only come off with the breaker turned off.

Sediment is the other common cause, and it shortens the hot water in two ways. Minerals settle on the bottom of the tank, occupy space that used to hold water, and bury the lower element. This August off Ashwood Drive in Port Richey, a tank was so packed with sediment that it was difficult to drain, the elements were caked with mineral deposits, and the bottom element was badly deformed from overheating. We replaced both elements and both thermostats and vacuumed out as much sediment as we could reach.

Sometimes the water heater is fine and the problem is somewhere else in the house. In Brooksville this January, the sinks were running very hot while the shower stayed lukewarm. The shower cartridge was stuffed with debris, and the tankless heater serving it was rated for 1.55 gallons a minute while the shower head ran 1.8. In Trinity this June, our plumber traced lukewarm water to a failing check valve that had been letting cold water cross into the hot side, and the heater had been turned up over time to make up for it. A single lukewarm fixture, or lukewarm water everywhere with the heater clearly working, points to a mixing valve, a cartridge, or a crossover rather than the tank.

Most tanks leave the factory set at about 120 degrees, which is the setting the Department of Energy recommends. Turning the thermostat higher stretches the hot water a little, but it also raises the risk of scalding, especially for small children and older adults. If you need more hot water from the same tank, a thermostatic mixing valve lets the tank run hotter while the faucets stay at a safe temperature.

When the cause is a failed element or thermostat, the repair is usually modest. Our published planning range for element and thermostat repairs is $300 to $495. Turn the breaker off before anyone opens the panel, because these are 240 volt circuits. In September of last year a homeowner off Brass Lane in Holiday had replaced the upper element without help, only to have the lower one short out, and the plastic wrench from the store could not break it loose. A replacement fifty gallon electric tank is a larger number, and the Spring Hill installation came to $2,101.50 with a new shutoff valve and an expansion tank.

Here is when you should not spend money with us. If the hot water lasts twenty minutes or more and then fades, run the math before you call anyone. Multiply the gallons per minute stamped on your shower head by the minutes of hot water. If two people shower back to back, or two heads run at once, a fifty gallon tank is being asked to do the work of a much larger one. A lower flow shower head, ten minutes between showers, or a mixing valve may solve it for far less than a repair. If the tank is ten years old or older and the lower element has failed, a new element is a short extension rather than a fix, and that money is usually better put toward replacement.

Farrell Plumbing repairs and replaces water heaters in Spring Hill, Brooksville, Hudson, Port Richey, New Port Richey, Holiday, Trinity, and Palm Harbor, and every installation is permitted and inspected. Farrell Plumbing holds Florida license CFC1430362.