Originally Posted by HiJoeSilver
Original would have been 1/2" main line with 3/8" teeing off to each appliance. If the trailer is shorter than 23" you can go with 3/8" for the main line if you need to pinch $. Longer than that you get to much pressure loss in the 3/8 main line to meet the BTU load if more than the furnace is running at the same time. You can do 1/2" to furnace tee then 3/8" aft.
Using 1/2" OD tubing for the main might work, but was not original, per service manual and my old set-up. Also something to consider, all the new (as opposed to the original) regulator-to-main hoses I could find have 1/2" or smaller fittings, so a step union was required. A 1/2" OD main would avoid this, and might be a better and cheaper option.
I just finished working through this part of my redo and need to check all my fittings for leaks next. I'll be using a different leak check method than the PO apparently used (see below).
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