Clarification - Plumbing Problems with our 1965 Overlander
Thanks to those who responded - to clarify the problem:
Using the tub spigot (with or with our without shower diverter) causes the water in the entire trailer (including the tub) to shut down temporarily.
In other words, when we turn on the faucet/spigot in the tub, water runs out for about 20 seconds at full pressure and then water only trickles out of the tub faucet; there is no further water in the tub at all. At the same time, (after about 20 seconds of full-water-flow from the tub spigot), when the tub spigot is open, there is no water anywhere in the trailer, e.g., no water in the kitchen or bath room sinks, or the toilet. Could this be a problem with the tub spigot?