[LazyPup]

Based upon the symptoms you describe I would be very hard pressed to recommend replacing the whole water heater.

You state that your hot water is running out after 5 minutes in the shower. Allowing that the old style shower heads had a flow rate of 5gpm while the new water savers have a flow rate of 2.5gpm at the end of five minutes depending on what type of shower heads you have, you have consumed somewhere around 12.5 to 25gal of water.

Typically a 50gallon electric water heater has a “First Hour” rating of 50 to 60gallons, which means that if the tank if full of hot water when the flow begins, it should be capable of delivering 50 to 60gal in the first hour of the demand. Obviously your water heater is not delivering the expected first hour flow rate so we must now consider what could cause the problem.

Ask yourself a simple question. If you have a hot cup of coffee sitting on your desk while your reading this, and if that coffee gets cold, will you throw the cup away or will you simply pour out the cold coffee and get another cup? Just like in our illustration with the coffee cup, if the tank is not leaking there really is no justification for replacing the whole water heater.

An electric water heater is simply an insulated steel pressure vessel with, a Temperature & Pressure relief valve, a drain valve, a dip tube, two thermostats and two heating elements,

We can instantly rule out the drain valve and the T&P valve as the cause of your problem.

Based upon the symptoms you describe and understanding that this is a sight unseen diagnostic, my best guess is that you either have a defective dip tube or the upper thermostat or upper heating element is not working.

You previously stated that the elements have been changed, however there is the remote possibility that the new element has failed. Given that accessing the thermostats and heating elements is fairly simple it would be prudent to thoroughly check both thermostats and heating elements before taking any further action.

The quickest and best method of checking the heating system is to use a “snap on amp meter”. You simply snap the jaws of the amp meter over one wire on the lower heating element then open a hot water faucet. Within a few moments you should see an amp reading indicating both the lower thermostat and heating element are working. Continue running the hot water and in a few minutes the lower element will turn off, indicating a zero amp draw. When you get the zero amp draw, remove the amp meter from the lower element and attach it to the upper element. If it shows an amp draw at the upper element both the upper thermostat and upper heating element are working.

Let us consider the dip tube. The dip tube is a plastic tube inside the water heater that extends downward from the cold-water inlet to a point near the bottom of the tank. The purpose of that tube is to carry the incoming cold water to the bottom of the tank while the hot water is discharging from the top of the tank. If the dip tube were broken the coldwater would discharge into the tank near the top. This results in diluting the stored hot water near the top of the tank and the end result is a rapid drop in the temperature of the water leaving the tank.

Before you begin the procedure to replace the dip tube you should get a new dip tube for your water heater. To insure you get the correct dip tube you will need to know the Make and model of your water heater then go to a plumbing supply house or a local neighborhood hardware store such as an Ace hardware or True Value hardware. (Most big box supply centers don’t want to be bothered with trivial items like dip tubes) They may not have your particular dip tube in stock but most will be glad to order you one. Expect to pay about $10 for a dip tube.

To replace a dip tube you pull the electrical service disconnect and turn the cold water supply valve off, then you will need to drain the tank. Once the tank is drained you disconnect the cold-water supply line and if your tank has dielectric nipples, you will need to remove the nipple from the cold-water inlet port. The dip tube is simply a plastic tube that drops down the cold-water inlet port and is held in place by a small flange on the top of the tube.

You pull the old tube up and out, then drop the new tube in place, reconnect the pipes and fill the tank.

NOTE: if the old dip tube should happen to break off inside the tank; that is not a problem.

Now let us consider the economics of completely rebuilding an electric water heater as opposed to replacing it.

You stated that you already have a price of $400 for a new water heater +2hours labor as a DIY project.

Now let us consider a worst-case scenario where you need to buy all the parts for a total rebuild:

Upper Thermostat…………………………………..$13.00
Upper heating element (220v 4500watts)…………..$10.00
Lower Thermostat…………………………………..$12.00
Lower heating element (220v 4500watt)………...…$10.00
Temperature & Pressure Relief valve………………$10.00
Brass boiler drain cock……………………………...$ 8.00
Dip Tube…………………………………………….$10.00
TOTAL REBUILD PARTS COST…………. $73.00

DIY Labor estimate.. 2-4 hours

Now consider this. Sears sells a Craftsman snap on amp meter for about $60. If you opted for a professional grade such as the Sperry SPR 300 that I use, you could get it for about $150.

Even if you had to buy the test instrument you could still end up with essentially a new water heater for 1/4 to 1/2 the price of replacing your existing unit.