Getting Hot Water in Your Rig
If you're new to RVing, it can be difficult to figure out why you have no hot water in your rig. There are several valves that need to be in the right position for you to have hot water. Having one of them set the wrong way can make you think there's something wrong with the water heater when it's actually fine. If you follow these steps in order, you'll know for sure.
Not every rig is the same, and some rigs have only gas hot water, while others have both gas and electric service. This section assumes that you have both, but you should be able to figure things out if you only have one.
First, turn off the water heater. The switches are usually under the kitchen sink - one for gas, one for electric. If your rig doesn't have a dual-source water heater, there will only be one switch. The electric one will have a little lightning bolt on it. They usually light up when on, but sometimes the lights burn out. They are usually rocker switches, and rocking the switch up (pressing on the top half) turns them on. Press on the bottom half to turn them off.
Next, turn off the water pump in the rig. Usually, there's a rocker switch near the water heater switches. Typically, it only rocks one way. Pressing it once turns the pump on, pressing it again turns it off. Usually, a light comes on when the pump is on, but if not, you should be able to hear the pump run when it's on and you turn on a faucet. Turn off the faucet once you're sure the pump is off.
Now hook up a hose to the city water connection in the utility bay (usually near where the black and gray tank valves are). Be sure *not* to hook up to the black tank flush connection if you have one. Turn the water on at the other end of the hose.
The bypass lever (if you have one) in the utility bay (where you hooked up the water hose) allows you to fill the fresh water tank in one position. In that position, you'll hear the water going into the fresh water tank. In the other position, water gets delivered to the rig's plumbing system. In that position, the flow will soon stop when the system is pressurized and you'll hear nothing (that's the position you want).
Many rigs have an outside shower. There's a spray attachment for outside showers, also usually in the utility bay. There are two knobs (hot and cold) that turn on the water to the sprayer. They're on each side of the sprayer and look just like the knobs on a kitchen faucet. If one of them is open (not turned all the way clockwise), no water will be coming out the sprayer, but hot and cold water will mix in the system and you'll get a cold shower inside. Pull out the sprayer and press the lever on it. If no significant amount of water comes out (it may drip a little), the knobs are shut off (what you want). Leave them closed.
Next, check the hot water tank from the outside of the rig. There's a square metal cover with a louver in it. You'll see a D-shaped latch somewhere near an edge and hinges on the opposite edge. Turn the latch 90 degrees and pull out on the cover and it will swing open.
Most rigs have a hot water bypass valve near the hot water heater (you may have to look under the rig or in a nearby compartment to find it). On some rigs, the valve is near the fresh water hookup. If that's the case, there may be two bypass valves there. You want the one that refers to the hot water heater. The valve basically takes the water heater out of the system. It lets you winterize the rig without filling the water heater with antifreeze and lets you bypass the water heater if it springs a leak.
The key to telling if the hot water heater is bypassed or not is whether water (or at least pressurized air) shoots out when you lift the pressure-relief valve near the top in the water heater bay outside (stand to one side!). You should see a little hot water warning tag around the valve. If you get water there, the water heater is full and pressurized (what you want). If the water heater bypass valve is the wrong way, you may have to wait a while after switching it, though you should have air coming out the relief valve while the hot water tank is filling.
Once you get a good stream of pressurized water coming out of the pressure relief valve, close it and turn on the water heater under the kitchen sink. With the gas one alone, you should hear the water heater fire up and continue to burn. If it lights but won't stay on, something is wrong with the gas hot water system. If you're using the electric, be sure the rig is plugged in to an AC outlet and that you have AC in the rig. The microwave clock or the TV are good indicators. The lights in the rig are mostly 12 Volt, so they are *not* good indicators. It's OK to turn both gas and electric hot water switches on if you need hot water in a hurry, but try them individually when you're testing.
Go to lunch. At least an hour later, see if you have very hot water in the kitchen. If so, you're done. If not, something is wrong with your water heater or a fuse that controls power to it.
If you know the fuses are OK and you still have no hot water, there are several things you can check. If there's no hot water on either gas or electric, the most likely problem is the thermostat. If you get hot water on gas, but not on electric, the typical culprit is the heating element inside the heater. It can be tested and replaced if defective.
If the gas burner tries to light (you can hear it clicking)and either won't light or won't stay lit, the odds are good that there's a problem with either the fuel supply or the burner assembly.
To check the fuel supply, see if the stove burners will stay lit. If not, make sure the valve is open at the LP tank (turn it counter-clockwise) and the tank is not empty. If the stove burners light but you see a lot of yellow flames instead of blue, it usually means that there is some air in the lines. Turn on all the stove burners and wait for the flames to turn blue, then turn them off.
If you get solid blue flames on the stove burners and the water heater still won't stay lit, it's time to check the burner assembly. Make sure everything is nice and cool before you start work. If you open the door on the hot water heater and look around, you should be able to locate the flexible hose supplying the gas, the valve that it runs into, and the metal tube running to the burner and the chimney. Most often, the problem is actually in the tube that carries the gas to the burner assembly. Mud Daubers and other wasps sometimes like to build a home in various parts of the system and spiders love to build webs and lay eggs inside the tube.
I once removed a wriggling ball of about 1,000 tiny baby spiders from mine. I saw the mother scurrying off behind the burner assembly, and about a day later, I received a painful spider bite in my bed. When I turned on the light, I discovered a brown recluse spider resting on my pillow. The bite itched and stung for about six weeks. Luckily, I didn't develop have some of the more serious problems that can occur with a brown recluse bite, but I can't help but think it was a mother's revenge for the mass murder of her offspring.
You can usually remove the tube with just a screwdriver. Once it's out, you can look inside and use compressed air to blow out any obstructions (or use a cotton swab if the problem is near the end of the tube). If you don't have a compressor, you can get a can of compressed air for cleaning computers from an office supply store or Radio Shack.
Less often, the problem is in the burner itself — crud in the jet, carbon build up, or some other obstruction. You can sometimes shoot a little compressed air into the area and clear things out.
If none of the techniques above work, it's probably time to call in an expert unless you have the equipment and skills necessary to do further diagnosis.
Thank you for visiting BobsGuides.com
— Bob Ray