Trailmanor, Suburban Water Heater LP Leak 

See Solution At Bottom!
We had a gas, LP, leak on our refrigerator. Once we repaired the leak on that, I installed an LP pressure gauge between the LP tank and the supply line. Turned it gas on, purged all the air out of the system and then turned the valve OFF. If there are zero leaks, the pressure gauge should remain unchanged for a long time.
What we found was that after about 6 hours the pressure on the gas line was almost down to zero on the gauge. That meant that we still had a leak. We have spent hours soap testing every fitting, lines, valves, etc, etc. No joy! Got a leak and can't find it.
Today, Kathy pushed me to buy a LP gas sniffer. We got it from Home Depot. I went back through everything with the sniffer. No joy. Then Kathy in her methodical fashion started checking. Well...she found the leak. I had previously checked this with soapy water...but the bubble was so small that I just missed it.
SOLUTION:
It turns out the gas valve assemble was failing. It was not holding the gas pressure. I ordered the gas valve from Amazon.com. This is a Link to the Part from my Amazon Associates Account.
amzn.to/3SzvKht
Hopefully the video will answer the mystery question!