House Calls with the RV Doctor
By Gary Bunzer
Dear RV Doctor:
We have a single-lever faucet on our shower that has a continuous drip when the water heater is on. I carefully replaced all the parts within the faucet with a kit, but to no avail. I understand that as water heats it expands, but where does the water normally expand to, and how does it seek relief? I know that some water leaks through the water tank relief valve, but that is not an option that I like either.
Leon Hill, F200575, Belleville, Ontario, Canada
Leon, I, too, would suspect a faulty seal inside that faucet, but if you’ve replaced the guts with the proper components, we can probably rule that out as a cause. And you are correct that as water heats, it expands. Normally this expansion occurs inside the water heater. A cushion of air must always be present in there to accommodate the expansion. In optimum circumstances this cushion of air inside the tank above the water level acts as an accumulator of sorts. Over time, this air space (oxygen) is fully absorbed by the oxygen molecules in the water. This results in no place for the expanding water to move into since the tank is, at that point, completely full. As you mentioned, usually the integral pressure and temperature (P&T) relief valve then performs one of its safety functions and opens, expelling the heated water through the P&T valve. This also allows additional cold water to enter the tank (thus lowering the temperature) and causing the valve portion to close. Perhaps the lesser resistance to this expansion is through the shower faucet instead of the relief valve. It is normal for the P&T valve to drip a little during each heating cycle.
I’d try renewing that air cushion inside the water heater. There’s a good chance that air space has been eliminated over time. To re-establish the cushion of air inside the tank, remove the water source by either turning the demand pump off or by interrupting the flow of city water. Open any two hot water faucets in the coach. Next, open the manual lever on the relief valve until the water flow completely stops. Close the P&T valve and the faucets, and then turn the pressure back on. There is now a cushion of air trapped above the water level inside the water heater once again. I’m hopeful this will eliminate that pesky leak in the shower faucet. I’d be tempted to install another faucet if the leak persists.
Hydro, Not So Hot
Dear RV Doctor:
We own a 1999 Safari Serengeti with a Hydro-Hot heating system. The system will run for a while, then the fire will go out, causing a flame-out warning light on the panel to illuminate. Sometimes it will go on and off like it’s getting air in the line. I’ve bled the line as per the manual but continue to have this problem. This makes for some cold mornings, as the thermostat continues to run the zone fans without any heat coming from the radiators. Any ideas?
Greg Peterson, F278921, Bremerton, Washington
Hydro-Hot units are relatively complex in their operation, but I will list the most likely components. I would, however, recommend having your unit serviced at an authorized repair center. Having said that, I suspect that your problem may be simple yet often overlooked. Although they are quite reliable, these units do need periodic maintenance. Even though the problems you are experiencing may be caused by component failure, it’s more likely that normal wear is the culprit.
Check the water/coolant level to make sure it is correct. Annual replacements of the fuel filter and fuel nozzle, in addition to cleaning the combustion chamber, are required in order to keep Hydro-Hot units operating properly. If either of these fuel components is clogged, dirty, or otherwise faulty, it could easily cause the problem you are describing. You did not mention whether you have had regular maintenance and consumable replacement done on your unit, but the first thing I would do is replace both the fuel filter and nozzle. Check the fuel screen filter located in the fuel supply inlet of the fuel pump for dirt particles. Clean or replace if necessary. Also, check for water in the fuel filter inspection bowl. As with all electrical devices, check all the wiring connections at the control module and elsewhere to make sure they are clean and tight.
You can check for air in the fuel line quite easily. First, ignite the burner and listen for a sputtering sound from the exhaust system. If there is a constant sputtering, then there is likely to be water. Clamp off and remove the fuel return line and attach a short piece of hose to the fuel return port. Place the other end in a container of diesel fuel and ensure that it is completely submersed in the fuel; then turn the diesel switch on. If air bubbles are visible in the container of fuel, inspect the fuel system (supply side) from the vehicle’s fuel tank to the diesel burner.
Inspect the fuel system for loose fuel connections at the Hydro-Hot and diesel burner, as well as at the vehicle’s fuel tank, and tighten if necessary. Also, check that all fuel filter head fittings are securely tightened. Be sure to check that each fitting at the fuel filter head contains thread sealant. A fitting without thread sealant could result in an air leak. Be sure to clamp off both fuel lines at the filter head prior to any fitting removal. If fittings are removed and reinstalled, be sure to remove the fuel line clamps prior to attempting a heater restart. Failure to do so could result in serious damage to the diesel burner’s fuel pump.
It is certainly possible that other components could be faulty, but since the burner ignites initially before going out, complete component failure is unlikely. Possible culprits include the fuel solenoid, which could be sticking or otherwise intermittent; the control board; or the fuel pump. Less likely are the ignition coil, electrodes, flame sensor, and motor.