Dual stage propane regulator

Off side (LH) propane cylinder has that single stage regulator to drop cylinder pressure down to 30# PRIOR to going across front of rig to the 2 stage main regulator where system pressure is dropped to 0.4#

Reason for that 'regulation/requirement' is full cylinder pressure (between 100# and 200#) in that long hose over time can become liquid when not used.
Liquid will destroy a regulator

The other NFPA Regulation for propane is 5.3.11.1
**The regulated high pressure piping shall be located entirely on the exterior of the vehicle or in a compartment vapor resistant to the vehicle interior

So short high pressure hose to 30# regulator is inside the off side propane compartment then Low pressure propane runs across front of RV INSIDE the front cap.

Thanks for all the info.

Exactly correct. It's a must have.

The hose from the left tank runs under the bedroom of the trailer, don't want high pressure there if it blows up.

I think he's referring to this:

5.3.11.2 Propane system pressure shall be regulated to a pressure of 30 psi (206.8 kPa) or
less within 60 in. (125.4 cm) of the container outlet.

...and the one tank is more than 60 in. away from the switchover regulator.

BB_TX wrote:
The single stage high pressure regulator is there as a requirement by the National Fire Protection Association Standard for Recreational Vehicles to drop line pressure to 30 psi.

I understand what you are saying, but, why does the left side tank pigtail go through a single stage regulator, then the pig tail from the regulator connects to the main dual stage regulator. The tank on the right connects directly to the two stage regulator.

The single stage high pressure regulator is there as a requirement by the National Fire Protection Association Standard for Recreational Vehicles to drop line pressure to 30 psi.