So, what are you supposed to do when your RV water heater is not getting hot enough? The first thing you should do is check the bypass valve to make sure it is closed. If left open cold water will mix with hot water and you will have water that is not hot enough.
But, there could be other issues causing this problem, as well. So, let’s dive into what to do when your RV water heater is not getting hot enough.
Water Heater Basics
There are two types of water heaters in an RV. A water heater with a tank and a tankless water heater and either type can use gas or electricity to heat the water.
A water heater with a tank simply uses electric heating elements or a gas burner to heat the water inside the water tank. The tank style of water heater is the type found most often in RVs. Once you turn on the water heater you have to wait a little while for the water to heat up inside the tank. And since most RV water heaters hold about 6 gallons they can run out of hot water quickly, which is why most folks turn off the water between washing and rinsing themselves. Below is a diagram of electric and gas water heaters with tanks that you would find in your home. Except for being larger, they work the same way as the one in your RV.
Tankless water heaters can use gas or electric to heat the water too. However, in my experience, electric tankless water heaters don’t work nearly as well as gas tankless water heaters. Tankless water heaters work by heating the water as it passes through a heat exchanger. When the hot water is turned on at a faucet or shower head in an RV cold water flows into the water heater and a gas burner or an electric element heats the heat exchanger which heats the water very quickly. Therefore, tankless water heaters can provide a constant supply of hot water. Below is a diagram of a tankless water heater.
How Long Does it Take for an RV Water Heater to Heat?
A 6 gallon RV water heater with electric or propane gas will take about 10 minutes to heat up. We only turn on our 6-gallon water heater when we need it so we don’t waste propane and 10 minutes is all it takes to heat up. A 10-gallon tank will take about the same amount of time to heat up.
Tankless water heaters provide endless hot water but contrary to popular belief, not instant hot water. It takes several minutes for the heat exchanger to heat up to its maximum temperature so it can heat the water quickly enough to keep up with the water flow. Many people are put off by waiting several minutes for the water to heat up. A gas tankless water heater will heat up faster than an electric one but with either type, there is a wait. On the upside, once it is operating at a high temperature you can maintain a flow of hot water without running out. This is great if you have full hookups and can continuously drain your gray water tank. But otherwise, you will be using as little water as possible so you don’t fill the gray water tank too fast.
RV Water Heater Not Working
Many RVers write into forums asking “Why is My Water Warm Not Hot” or looking for an answer why their RV water heater is not heating. What most of these folks are saying is that they can hear the propane kick on and run, but they are getting luke warm water rather than hot water through their faucets or shower. Luckily, there is usually a very simple answer to the problem.
Many RVs have what is called a Water Heater Bypass Valve. It is used when RVs are winterized and it keeps RV antifreeze from entering the water heater. When the bypass valve is used to winterize the RV it will be in the open position so that water goes through the pipes to and from the water heater but not into the water heater itself. In the spring when the RV is de-winterized, if this valve is left open the hot water will mix with the cold water supply resulting in lukewarm water rather than hot water at your faucet or shower head. Check out the diagram below to see a bypass valve set up.
In the picture above all three valves are in the open position so the blue cold water line is taking water into the hot water heater and it’s also adding cold water to the red hot water pipe coming out of the water heater. This valve needs to be closed so cold water does not mix with the hot water coming out of the water heater. Otherwise, you will end up with warm water.
Another similar issue that can cause warm water rather than hot water can be open valves at an outdoor shower on a rig. Most outdoor showers have a hot and cold water valve. When you turn them on the water mixes between the valves and the shower head. If you just turn off the water at the shower head and do not close the valves, the hot and cold water can mix and create warm water inside your RV too.
RV Water Heater Troubleshooting
No Hot Water
If you have no hot water the first thing you need to do is check to see if you have gas flow and if the pilot light is on. If the pilot light is on, there could be a problem with the thermocouple. It may not be recognizing that the pilot light is on and therefore will not ignite the gas. The thermocouple may need to be cleaned or replaced.
Not Enough Hot Water
There are several reasons for not having enough hot water or for running out of hot water too quickly. The reasons could be a malfunctioning thermostat, a broken or damaged dip tube which would allow cold water to mix with the hot water at the top of the water heater, or having the water temperature set too low. Sometimes it just boils down to having a water heater tank that’s too small for your needs. It’s not always practical to install a larger water heater in an RV so maybe a tankless water heater is an answer.
The Water is Too Hot
If you RV in colder climates it’s possible that you have the thermostat set too high. This can occur when transitioning from colder weather to the warmer weather months and forgetting to reset the temperature after raising it to account for the colder winter temperatures. It’s also possible that the thermostat needs to be replaced.
Water Heater Takes Too Long to Recover
If your gas water heater recovers too slowly, the thermostat could be set too low, the burner assembly may need to be cleaned, the propane gas pressure may be too low, or the vent flue may need to be cleaned. But in most cases, it’s just using water faster than the water heater can heat water.
RV Water Heater Won’t Light
If you know how to light the water heater pilot light but it still will not ignite there could be several reasons why. There could be air in the gas line, the thermocouple could be loose or defective, the pilot light opening could be dirty, or the gas valve could be broken.
RV Water Heater Pilot Light Won’t Stay Lit
I can’t think of anything more frustrating than a pilot light that will not stay lit. Usually, when this happens it means the thermocouple needs to be replaced. Other likely reasons include a bad gas valve or a partly obstructed vent.
The Burner Will Not Stay Lit
If the burner intermittently goes out, makes an unusually high or low flame, or a whistling sound it is most likely because of clogged burner openings. A malfunctioning thermocouple or dirty vent could also cause the problem.
The Water Has a Rust Color
If you see rusty colored water it could be the water itself or the anode rod could be corroded. The inside of the water tank could also be corroded which means you will need to replace the water heater. It’s very easy to replace the anode rod and flush the water heater as we cover in the next section below.
The Hot Water Smells Bad
There are two main reasons for hot water that smells bad. Either the anode needs to be replaced or there are bacteria in the water heater tank. Clean out the tank with chlorine and water and if it still smells bad you probably need to replace the anode rod.
RV Water Heater Maintenance
The single most important maintenance item for your water heater is to drain it periodically. Draining your hot water heater will help to keep it free of sediment which reduces the tanks ability to heat the water efficiently. To drain the water heater follow the steps below.
- Turn off the water heater (110V and LP) and allow it to cool completely
- Turn off the secondary 110V switch on the back of the water heater
- Turn off the city water and the water pump
- Open the hot and cold water faucets
- Open the pressure relief valve on the water heater
- Once the pressure is reduced, use a 1-1/16” socket wrench and unscrew the anode rod
- Drain the tank completely
- Clean out the sediment at the bottom of the water heater tank using a wand attached to a water hose
- Reinstall or replace the anode rod and use Teflon tape to prevent water leaks
- Do not over tighten
The RV water heater is an important part of enjoying the RV experience and getting a nice hot shower while on the road. Hopefully, you are a little better informed about RV water heaters and how to troubleshoot and maintain your water heater. If you are ever unsure about what is causing your water heater to malfunction and you are not comfortable working with your water heater please call an RV technician to asses and repair the problem.
Thanks for reading the article! Do you have any water heater advice to pass along? Please leave a comment below.
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