For the past several weeks I have been writing about RV plumbing. I will now shift focus to appliances and will discuss water heaters this week and next.
Water heaters, like most RV appliances, don’t require much maintenance, but it is important to understand how they work in order to keep them functioning properly. Understanding basic terminology and operation also helps if something goes wrong so you can either troubleshoot it yourself or better understand the repair details as they are explained to you.
There are a number of different manufacturers, models, and sizes available. The two primary players are Atwood and Suburban and the general sizes are 6 gallon for average RV’s and 10 gallon for larger units, although smaller and larger models (from 3-12 gallon) are available. In terms of models, there are pilot, direct spark ignition (DSI), and DSI/electric. Motor-aid is also available for use in motorhomes. These utilize engine coolant to assist with heating the water. In addition, tankless instant heat models have appeared on the market recently. However, in this article, we will only be discussing standard water heaters.
Although Atwood and Suburban water heaters are basically identical in form and function, there is a significant difference in that Suburban utilizes a glass-lined steel tank while Atwood uses aluminum. This is largely irrelevant to the end user except for how electrolysis is handled. Electrolysis, or galvanic corrosion, occurs due to the interaction of compounds suspended in the water (especially hard water) with the water tank, resulting in damage to the tank over time. For steel tanks such as Suburban, an aluminum anode rod is used, which is sacrificed instead of the steel of the tank. For Atwood and other aluminum tanks, the tank itself acts as the anode to the minerals. Therefore, if you have a steel tank, be sure to regularly inspect the anode rod and replace it when it is no more than 75% consumed. Be sure to use teflon (PTFE) tape on the threads. Never replace the anode rode with a plug. For aluminum tanks, do not use an anode rod, and always use a plastic plug. Do not use a steel or brass plug, as the dissimilar metals can cause severe corrosion, making the plug difficult or impossible to remove.
It is quite common for the P&T (Pressure & Temperature) valve to drip or leak occasionally. This generally just means that either the air space at the top of the water tank has been absorbed by the water or there is some debris trapped in the valve. If this happens, briefly open and release the P&T valve. If the leak was caused by debris, this will usually dislodge it. If the valve still leaks, turn off the water pump or park supply and open the closest hot water tap to the water heater. Then hold the P&T valve open until no more water flows out of it. Turn the water supply or pump back on and close the water tap as soon as there is no more air escaping. This will restore the air pocket and eliminate the drip. The other possible causes of P&T valve weeping are excessive temperature or faulty P&T valve. If the water temperature is too high, you will likely need to replace the thermostat or ECO. If the temperature is normal, replace the P&T valve.
In part 2 of this article, I will talk about what to do if you don’t have any hot water.
About the Author:
Steve Froese, an avid RV owner, traveler, and Coach-Net member since 2013, is the principal of “A Word to the Wise Technical Communications”, a published RV author, certified RV technician, and licensed Professional Engineer. He frequently collaborates with the “RV Doctor”, Gary Bunzer, and has worked with the RVIA/RVDA as a technical and training writer and consultant. Professionally, he works as a quality engineer and musician. Watch for more of Steve’s work in upcoming Coach-Net publications.