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Electric Water Heater With Only 5 minutes of hot water.
This is a continuation of, " How to troubleshoot an electric water heater". If you did not read the previous page please go back by clicking here.  You must read the previous page and all the warnings first.
I only have 5 minutes of hot water and it gets cold.
There are a number of reasons for this type of problem.

First we need to eliminate the ones that have nothing to do with the water heater. check all of your faucets, make sure there are no drips, check all your toilets, make sure they are not running. Did someone just run the dishwasher? Did someone else just take a shower, or do laundry? Ok, Now lets get to possible water heater problems. 5 things come to mind.

1 The water heater is too small for your needs
1 If the water heater was doing just fine before, you can eliminate the heater being to small for your needs.

2. The dip tube has broken.
2 the dip tube is a plastic tube inside the water heater (not the tube that is connected to the relief valve) on the cold water inlet side. this tube goes from the top of the water heater to about 8 inches from the bottom of the tank, forcing the cold water to go to the bottom of the tank, pushing the hot water out of the hot outlet of the water heater. If this tube brakes say 12" in to the water heater, any hot water below that point will not be available. it will just be trapped there. And even though the tank is full of hot water, you will just get a small amount of it. Replacement tubes are available at any plumbing supply. The cold water pipe will need to be removed to replace the tube.
It may be better to call a Pro.
See how the dip tube works

3 The lower element has burned out.
3 The lower element has burned out. this is the most common reason. but don't assume. To test, make sure power is off Read warning above remove cover from lower element remove both wires from element. use meter to test for continuity. If it has none it needs to be replaced. if it shows poor continuity it needs to be replaced. If it shows good continuity the element is good and there is some other problem.
To replace the lower element. Again make sure the power is off. turn the water off. open any or all hot water faucets, connect hose to water heater and drain it. if water does not flow, make sure you have opened at least one hot water faucet. if it still does not flow. try blowing in to the other end of the hose. to clear some of the sediment from the drain. If it still won't flow. Your tank may be so full of sediment that it will not allow the water to flow. If this is the case it may not be worth replacing the element. Go shopping for a new water heater. If you do get it drained make sure you get the right element for the water heater you have the size and wattage must be the same. most plumbing supply stores have all the parts you will need for your water heater. They also have the tool for the screw out type and the 4 bolt type takes a standard socket wrench. using the tool unscrew the element, Make sure the rubber washer comes out also and the area for the rubber washer is clean and clear of any debris. Make sure the new washer fits into it's place and then screw the new element In to the water heater being careful not to pinch the rubber washer make tight. close drain fitting and turn water back on, leave the hot water faucet on till all the air has run out and a steady flow of water is running out of the faucet. then turn off all faucets. and check for any leak around the new element. If you are sure there are no leaks, reconnect the wires. put the protective plastic cover over the thermostat and the element wires replace the cover. then put the power back on. It may be better to call a Pro.

4 The lower thermostat is bad
4 The lower thermostat is bad. To test for this you need to use a meter that can read 240 volts. (a 120 volt meter testing against 1 pole and a ground will not tell you if the thermostat is bad) Make sure the power is off until you have the cover off and the insulation and plastic protective cover removed. Then turn the power back on. Again if you do not know how to use an electric meter call a professional, you can be killed. You will see two wires coming from the top thermostat, one of them will go directly to the lower element. the other will go to the top of the thermostat. Note: remember the context of this part of the trouble shooting. You only have a limited amount of hot water, If you do not have any hot water. This does not apply. Before we can test the lower thermostat we have to be sure the upper thermostat is satisfied. So you will need to have both covers and plastic protectors removed before you turn the power back on. if the upper thermostat is satisfied, you will not get a 240 volt or 220 volt reading at the upper element. if you do leave the power on and wait. or lower the temperature of the upper thermostat till you no longer get a power reading at the upper element. (you will always get a 110 volt reading if you use a ground and 1 pole but this would be a faults reading) Once there is no longer a 240 volt reading at the upper element, . you should have a 240 or 220 volt reading from the 2 connections. Now test the screw on the bottom of the lower thermostat and the wire that goes to the lower element. If you have 240 or 220 volts the thermostat is working, if not it is bad and needs to be replaced. (assuming the water at the bottom of the water heater is cold and the thermostat is turned up to 12 degrees f ) To replace the thermostat MAKE SURE TO TURN THE POWER OFF. get the right replacement, there are only 2 wires remove the wires and the thermostat is just held in by a clip pull the clip away and it just lifts out. put the new one back the same way you took the old one out and reconnect the wires. Put the protective cover back on and covers then turn the power back on. It may be better to call a Pro.

5 the upper thermostat is bad
5 the upper thermostat is bad Read all of item 4 "the lower thermostat is bad" At the part when the upper thermostat is satisfied (no 240 volts to the upper element) test the top screw on the lower thermostat and the other wire that goes directly to the lower element. If you do not have 240 volts At this point (assuming you have read and understand Item 4 above) The upper thermostat is bad. To replace Make sure you have the right thermostat for your water heater, MAKE SURE YOU HAVE TURNED THE POWER OFF. The wiring may be set up a little different from the one that is on the water heater and the one you just bought, On the back of the package of the new thermostat, you will find a few different wiring diagrams, find the one that applies to your water heater. and follow it VERY CAREFULLY. Put protective covers back over wires, then put covers back on, then turn power back on. Note: make sure tank is full of water and you had a steady flow of water coming out of a hot water faucet before you turn the power back on. Failure to do this will burn out the elements. It may be better to call a Pro.

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