If your hot water runs out faster than it should, it is a sign of a bad lower heating element, broken dip tube or mineral deposits at the bottom of the tank.
Replacing the heating element or dip tube, or flushing out the sediments from the tank will in most cases fix this problem.
The first thing to ask yourself after noticing that your hot water is running out fast is whether the change was instant or gradual. A gradual change points out to mineral build up in the tank, while an instant reduction in hot water will be caused by a shorted/burnt out element or a broken dip tube.
A bad lower heating element, broken dip tube or sediment build up can all cause an electric water heater to supply hot water for a few minutes only. It will be a different scenario for gas water heaters since they do not have a heating element.
If a gas water heater is running out of water too fast, either the dip tube is broken or sediments have settled at the bottom of the tank reducing the water heater’s capacity. Replacing the dip tube or flushing out the sediments will likely fix this problem.
For a water heater that is more than 10 years old, it is noisy, the water from it is rusty and leaks often, a replacement is a better solution that trying to fix it. For more information on when to replace a water heater, check out this post.
New Water Heater Running out of Hot Water Fast
If you have a new water heater that is running out of water fast, the problem cannot be a broken dip tube or mineral deposits. It points out to an error during installation.
A new water heater that is running out of hot water faster than it should could be due to a burnt out heating element, reversed hot and cold water lines, wrong electrical connections among other issues.
If the water heater was powered without water inside the tank, it is very easy for one element to burn out, meaning only one element will be heating the water. Filling the tank without flushing out air can also lead to trapped air inside the tank which can burn the element as well.
It could also be that the water heater is not receiving the correct amount of power supplied to it. At any one time, there should be 240 volts of power flowing to the water heater. If the heating elements are only receiving 120 volts, you will have insufficient hot water.
Loose connections could also mean that only one heating element is heating the water.
To solve this problem, remove the access panels on the water heaters and test the 2 elements for continuity. Also check that they are receiving 240 volts of power and are properly wired. Check out this post for more information.
How to Fix a Water Heater that Runs out of Hot Water Fast
As I have mentioned, there are 3 main reasons for a water heater to run out of hot water faster than it should. Let us look at how you can fix the problems one at a time.
1. Test Heating Element for Continuity
An electric water heater will in most cases have 2 heating elements, and therefore 2 thermostats. If you are having hot water which runs out fast, you have a bad lower heating element.
When the upper heating element is bad you will not have any hot water. This is because power flows from the top thermostat to the lower thermostat. When the upper thermostat and heating elements are bad, power will not get to the lower element.
To check whether the lower heating element is the culprit, you need to test for continuity across its terminals. Doing this is really simple. You will only need a multimeter and a screwdriver.
Testing a water heater element for continuity:
Turn off Power to the Water Heater
You should never attempt to work on your water heater with power still flowing to it. As I have said above, there will be 240 volts flowing in the water heater, which is enough to electrocute you.
Head over to your main electric panel (in the garage, basement or storage panel). Look for the breaker marked “Water Heater” and flip it to the off position.
Remove the Lower Access Panel
Water heater elements and thermostats are concealed by 2 access panel, which are secured to the water tank using screws. You will need to remove the lower panel since that is where the lower heating element is.
- Use a screwdriver to remove the screws on the lower access panel and put them away in a safe place. You do not want to lose those screws.
- There will be a piece of insulation covering the element. Remove it out or hold it over the panel secured with a duct tape or electrical tape to the tank.
- You will also see a plastic cover which snaps on both the thermostat and heating element. Remove it as well.
With the above items out of the way, you can now see the element and thermostat. The heating element is at the bottom with 2 wires connected to it.
Test the Element for Continuity
- If you have an analogue multimeter, set the dial to the lowest ohms of resistance. Pinch the 2 probes together and move the needle to zero to calibrate it.
- With a digital multimeter, you only need to move the dial to the lowest ohms of resistance or set it to beep if you have that setting.
- Loosen the screws on the element and disconnect the wires.
- Place the 2 micrometer probes on the 2 water heater terminals and check the reading on your multimeter.
A good heating element will have a reading of 10-16 ohms. If it shows no resistance or it does not beep, the heating element is faulty and will need to be replaced.
- Place one probe on one element terminal and the other on the water tank body. Alternate the terminals but still maintain the contact with the tank.
If you get a reading or if the multimeter beeps, it means that the element is grounded and a replacement is needed.
Note: While you can replace the faulty element only, I prefer replacing both of them. That gives me piece of mind that I will not need to do it in a few months/years
Replacing a Water Heater Element
- Again, make sure that power to the water heater is turned off.
- Turn off the water heater cold pipe shut off valve.
- Drain the tank. Connect a garden hose on the drain valve at the bottom of the tank and open the valve with flathead screwdriver if it has no lever. As the tank drains, open the nearest hot water faucet to help it drain even fast. Leave the faucet open even after completely drain the tank.
- Using a 1 ½ inch socket wrench, grab the heating element and loosen it. You might need a breaker bar if it is too tight.
- Once the element is loose, remove the wrench, unscrew it with your hand and pull it out.
- Clean the threads and push in the new element. Do not forget to put the washer on the element to avoid leaks.
- Thread in the element until hand tight. Tighten it with the wrench.
- Open the water supply to the tank. Before this, make sure you have turned off the drain valve and removed the garden hose.
- As the tank fills with water, air will be flushed out through the faucet you left open. Only close the faucet when you see a smooth flow of water.
- Check if there are leaks around the new element. If none, connect the wires under the screws and tighten them together.
- Put back the plastic piece, insulation and cover plate
- Turn on the power to the water heater and wait for about 20 minutes for the water to be sufficiently heated.
- Fill your bathtub with hot water or take a long shower and see if the problem is fixed.
2. Replace the Dip Tube
A dip tube is a piece of plastic pipe inside the water heater that is connected to the cold water supply line. It directs cold water to the bottom of the tank to get heated, while hot water is pushed at the top of the tank ready for use
If the deep tube is broken or has cracked near the top, it fails to channel water to the bottom of the tank but instead deposits it at the top, which is then delivered to your faucets and showerheads.
Replacing a dip tube is not very easy and will in most of the time need a plumber to do it. Avid DIYers will however replace it easily.
To start with, if you water heater is supplied with water using solid copper pipes, you will first need to cut them and solder them later. You will also need to cut the dip tube with accordance with the size of your water heater.
If on the other hand your water heater is supplied with cold water using a flexible hose, this might be any easy repair for you.
- Start by turning off water supply to the water heater.
- Drain about 5 gallons of water from the tank. this will prevent water from splashing out while removing the dip tube.
- Use a wrench to disconnect the hot water line from the water heater.
- With the same wrench, loosen the dip tube and pull it out.
- Assuming you have already bought a new dip tube, compare the length of the new with the old tube and cut the new one accordingly.
- Apply Teflon tape on the lower threads of the new deep tube and stick it inside the water heater. Thread it until hand tight then tighten it further with the wrench. Be careful not to damage the threads. Slip-joint pliers are ideal for this job.
- Now apply Teflon tape on the exposed threads. Connect the water heater line back and tighten it.
- Turn the water and power back on.
If you are not comfortable cutting and soldering copper pipes, please make use of a professional plumber. Check out more on this solution in this video.
3. Flush out Sediments
The water flowing to your water heater will contain debris and minerals, which settles at the bottom of the tank and accumulate there with time. This is why you are advised to flush your water heater at least once per year.
If you have not been flushing the tank, I wouldn’t be surprised to find about 10% of the total volume of the tank occupied by sediment. The sediment can also cause the water heater to leak from the bottom.
For a tank that has not been flushed for many years, trying to flush it from the drain valve is almost useless. There is just too much sediment to flow out through that valve.
One trick you can is to remove the lower heating element of an electric water heater and suck out the sediment with a shop vac. For more information on that check out this video.
With a gas water heater the solution will most likely be a replacement especially if the tank is already 10 years or more in age.