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Don’t Look In There!
We took our first overnight trip (since our coach purchase in Nov. 2017, that’s another story) in the coach last week as a test of as many systems as possible. We only went about 10 miles from home. We uncovered a few things that need to be addressed. We have more questions now than before our overnight test trip. But first to the topic of this post.
The water heaters didn’t work exactly as we expected. We had both the 120VAC and 12VDC water heaters turned on. We expected the electric heater elements to keep the water hot most of the time and for the Webasto to kick in when the demand for hot water exceeded the capacity of the electric elements to keep up. We had a daytime high OAT of about 85F. Even with the electric elements on, the Webasto ran way more often than expected (about once every 1 ½ hours) even when there was no demand for hot water.
When we got back we decided to look at the water heaters. We had a small but constant leak from the pressure-temperature relief (p-t relief) valve on one of the water heaters. Before we got to that we got out the VOM and pulled the covers off the wiring for the water heaters and started to look around. First we found a burnt connector on the thermostat for the lower water heater. Maybe it wasn’t working during our test? We also found some of the wiring needed some attention. With all that in mind we drained the WH’s in preparation to change out the p-t relief valves. With the WH’s draining we started to see a lot of “stuff” (we think mostly lime scale) in the drain pan. Because it seemed to be a lot of “stuff” and not just a little we decided to replace both p-t relief valves, both heating elements, and clean the remaining “stuff” out of the tanks. We’re concerned that that “stuff” will work its way through the plumbing and start to clog up faucets and shower valves.
After removing the heating element from the top WH, here is what we found in the tanks.
It looks like replacement water heaters are in our future.
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3 Replies
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Hey Tim, I have an 07 Marathon and if those are the original water heaters you should replace them no matter what. At that age they are subject to problems.
You should not need to run the 12 volt (Webasto) heat while on generator or shore power. The 12 volt turns on the Webasto as you know to heat the water and is the least efficent way to do so but its great for dry camping. The Webasto will cycle often to keep the water hot.
When on generator or shore power use the 120 volt heat.
When going down the road the road the engine cooling loop will heat the water, you don’t have to do anything to turn on this feature
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Thanks for the info Buddy.
Replacement water heaters on order. We won’t run the 12 VDC water heater (Webasto) while on generator, shore power, or with the engine running for hot water…lesson learned.
I’m sure we’ll need more Prevost-Marathon lessons as time goes on. Thanks again.
P.S. Did you ever wonder what the tank looked like in one of those square Atwood water heaters?
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Check out these. https://www.westmarine.com/water-heaters
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