Originally Posted by JPBeck
Did you check the winterizing valves? If they are open there'll be a constant flushing of fresh water through the system.
Thanks JPBeck for the very clear photo of the bypass valve and to all others that commented on this subject. It helped a great deal for us.
We're in the 5th week of our inaugural trip. This entire time we have used the shower each day and we have had water that was luke warm at best. It finally occurred to me that I should search the forums for related items.
All posts that I found were about water that is too hot. Ours was the opposite. Our new trailer has the non-adjustable thermostat on the water heater that should heat to 140 degrees.
After looking at your pic above, I grabbed a flash light and crawled half way into our rear storage compartment. I found the hot & cold water lines (ours are red and blue respectively) and the bypass valve behind the water heater. Our bypass was opened all the way.
So I closed it about half way and now we have hot, hot water instead of warm. In fact I went back in and opened the valve a little more so that our water isn't too hot. So far so good.