by Roxanne Prather, Member Services Representative
How can I figure out why I have hot water in the morning, but it cools off during the day?
• Check to make sure that the thermostat is set right.
Your thermostat should be set to at least 120°F – 140°F. If it is set below or the thermostat is malfunctioning, the tank would only heat partially, therefore depleting your hot water faster.
• Faulty heating element
Upper element: Fires first after a cold start to quickly heat the top of the tank, giving you hot water fast. It also re-engages when cold water rises to the top during heavy use.
Lower element: Takes over once the upper zone reaches temperature, heating the bulk of the water to maintain a steady supply
No hot water at all: Often means the upper element is bad, because its thermostat also controls the lower element’s power.
Slow to heat up or runs out of hot water quickly: Usually points to a lower element issue, as it’s the main “workhorse” for maintaining temperature.
Only hot water at the top: Suggests the lower element is not working, so the bulk of the tank stays cold.
Cold water at the bottom: May mean the upper element is not heating the top zone, so cold water can rise and mix in. Use a multimeter to test the elements: If the element has continuity, it’s good; if it’s open (no continuity), it’s bad.
• To test the elements
Make sure power is shut off.
Access the elements: most have an upper and a lower element. Remove the metal cover and any insulation covering the end of the elements. Disconnect the element wires from the thermostat and label them to avoid any confusion when hooking them back up. Set the multimeter to the resistance (ohms, Ω) setting.
Test each element: place the multimeter probes on the two exposed terminals of the element A good element will show a reading in the hundreds of ohms (often 30–100 Ω for standard 240V elements).
If the reading is infinite (OL) or zero, the element is open or shorted
• Faulty thermostat
Upper thermostat failure: No hot water at all, lukewarm water, or both elements not heating. The upper thermostat is the master control — if it fails, it won’t send power to the lower element
Lower thermostat failure: Limited hot water or water that never gets fully hot, but the upper element may still work
Both failing: No hot water.
• Test the upper thermostat
Make sure power is shut off
Set the upper thermostat to the highest setting and the lower thermostat to the lowest setting. Disconnect the wires from the upper thermostat terminals. With the water temperature below the set point, use a multimeter in ohms/continuity mode to check for a near zero reading when the terminals should be closed. If there’s no continuity when it should be closed, the upper thermostat is bad. Also check the high limit reset button: if it trips and won’t reset, the upper thermostat may be allowing overheating
Test the lower thermostat: make sure power is shut off
Disconnect the wires from the lower thermostat terminals. With the water temperature below the set point, check for continuity. If there’s no continuity when it should be closed, the lower thermostat is bad. If you have hot water but it’s not fully hot, measure voltage at the lower element: no voltage means the lower thermostat is faulty.
• Sediment buildup and scaling-over time
Minerals and hard water accumulate as sediment at the bottom of the tank, this acts as an insulating layer that impedes heat transfer causing longer heat times and cooler water at the taps. This is more common when the tank is older if you have hard water. Regular flushing the tank in these situations can prevent this build up.
• Water heater size and demand
Make sure you have the right size water heater for your family size.
Quick sizing guidelines to ensure adequate hot water supply for daily use:
30-gallon tank : 1-2 people
40-gallon tank : 2-3 people
50-gallon tank : 3-4 people
50-60 gallon tank : 3-4 people with teenagers
60-80 gallon tank : 4-5 people-high peak demand
80-105 gallon tank : 5+ people- off peak programs
• Check the dip tube:
If you notice cold water after replacing the heater or after a long time this may be the cause.
