Pressure relief valve

[Danddandy]

How about 2 or more pressure reducers connected in line as a belt and braces. Just a thought. . . I'll get my coat. .

 

[ProfJohnL]

by the way are the pressure reducers sort of an intelligent devices or are they just built assuming they need to reduce the pressure from 6 to 2 regardless of the actual ingress pressure? If it's the latter I assume the egress pressure will be lower than 2 if the ingress is less than 6 (and vice versa)?

It depends on exactly what you are referring to, for example if you mean the device fitted in the direct mains water hoses, which need to be full function "regulators" (edit) their purpose is to prevent the outlet pressure from rising above a particular value, regardless of the input pressure variations, then yes they are active devices and adjust their valving according to both the demand and the supply. I wouldn't go so far as calling them "intelligent"

The device you have described is not a pressure Regulator it is , it is a pressure Reducer, and for the reasons you explained, it is 'Dumb' and it would almost certainly have poor flow characteristics at low input pressures. It would not be suitable to protect a caravan from mains water pressures.