Is the voltage per leg supposed to be 120 or 240?

If breaker trips check

- elements being to high in ohms resistance (worn out)
- shorted elements
- short to ground
- improper wiring or voltage per nameplate

That voltage does not seem high enough. Supposed to be 1.6 VAC and I got 2.5 VAC. Do you have the water flow turned to the maximum? Is there something blocking water flow? The hydro voltage should be checked separetly from everything else, so if you can't get the VAC higher, my guess would be that's the problem.

Yes
Voltage and wattage printed is on end of each element
If element shows 240V 4500 watt, then element Wattage at 208V is reduced to 3375 watts and will heat 16+ gallons per hour
If element is rated 208 and 4500w, then element will operate at 4500 watt and heat 20 gallons per hour
http://waterheatertimer.org/Figure-Volts-Amps-Watts-for-water-heater.html

http://waterheatertimer.org/images/Whirlpool-energy-smart-watt-rating-IMG_2600.jpg

http://waterheatertimer.org/How-to-replace-water-heater-element.html

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Testing voltage on heater can be tricky since elements can test 120Volt to ground all all times.
This is because thermostats only turn off 1 Hot leg in the 240Volt circuit, while the other hot leg remains live. Each hot leg in 240Volt circuit is 120Volt.
http://waterheatertimer.org/B220C.html#120-240
Troubleshoot electric water heater:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#reset
Try following things in order: Press reset button. Test elements. Replace thermostats.
http://waterheatertimer.org/How-to-test-water-heater-element.html
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html
Add comment.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) Check across top two screws on upper element for 240volts.
Circuit breaker can be tripped on one leg so water heater appears to have power, but only has 120Volts to ground, and not full 240Volt potential across both wires.
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#electricity

2) Move wires to another same-size circuit breaker
http://waterheatertimer.org/How-to-replace-circuit-breaker.html

3) Add comment and say what you find, and for more assistance Dec 2012

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

The incoming voltage should be 220-240. Check voltage across terminal that power supply is hooked to.Each incoming leg should read 120 to ground and 240 across . Check to see that thermostat is turned up to highest setting,usually 140 degrees,and check reset button to make sure it stays in in position. If you push reset in and it pops right back out you probably have a bad element. Check elements by going across terminals when you know element should be on.Hope this helps you. Thanks

If water is totally cold, then upper element is not getting 240V. Since element tested for 120V, then that says upper element is burned out, upper thermostat is bad, or circuit breaker is bad.
Best thing is to buy multimeter and do 30 minute troubleshoot:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

Also read information below for understanding how water heater works.

Testing elements for voltage can be misleading.
If water heater has 2 elements, then tank is 240Volts.
240V water heaters have 120V on each element at all times.
So elements have hot 120V power, but they are not turned on until the circuit is complete with 240V.
Open following links to read specifics about 120V and 240V
http://waterheatertimer.org/B220C.html
http://waterheatertimer.org/How-water-heater-thermostat-works.html

240V is made from two 120V Hot wires from breaker box.
Each 120V line from breaker is called a 'leg.'
So 240V circuit has two legs, and both legs need to be turned on to complete 240V circuit.

Water heater thermostats turn off only one leg.
The other leg is Hot all the time.
So when you test screws on an element, for example test between a screw and any bare metal part of tank, then the screw will always show 120V.
That is just one leg of the 240V circuit.
But the 240V circuit is not turned On until both legs are connected.
Every residential circuit needs two wires to complete the circuit, and in the case of 240V, those two wires are both 120V.

When the thermostat turns on, it turns on the second leg to the element and that completes the 240V circuit.
http://waterheatertimer.org/How-it-works.html

The heating element must be shot. There is an adj there, but it is a tiny dial, and I'm not sure about the 30 gal, but most heaters have 2 elements. If yours starts out too hot then runs out, Blame the element, or check the breaker with a meter to make sure you have voltage to both legs of the 220 volt line. Sometimes one will quit there, and leave you half power. Check it out.

two screws on the element ... two wires ... in most cases. You probably have 220 volts, make sure it is off.

check circut breaker reset it then chek for power on both legs.