RV Water Pressure: The Regulator, the Inlet and the Park Supply

What the makers publish

Four makers publish a target, and they agree closely. Winnebago's owner's manual recommends "regulators that control water pressure to 50 psi. max." Camco's fixed regulator is preset to 40 to 50 PSI according to its own product copy, and its adjustable unit ships at 45 psi with settings above 60 psi not recommended, a figure that appears in distributor listings rather than on Camco's own pages. Jabsco regulates 46 to 125 psi down to 45 psi, with a stated variance of plus or minus 5 psi. Blu Technology presets at 45 PSI and recommends 40 to 60 PSI.

Camco's own guidance describes the range differently from the way a preset might suggest. Its expert article says that "many standard, non-adjustable regulators are preset to 40-50 PSI to be safe. But, most RV plumbing systems can comfortably handle 55-60 PSI." That is the case for an adjustable unit: a fixed regulator protects the system at the low end of the range, and an adjustable one lets a reader sit higher in it.

Jabsco's regulator brochure gives the supply side of the same picture, describing unregulated city water pressures that "can run as high as 125 psi".

The tubing is not the weak point

Fresh water lines in an RV are usually PEX, and PEX is rated far above anything a campground delivers. Viega publishes a design rating of 160 psi at 73 degrees Fahrenheit and a minimum burst pressure per ASTM F876 and F877 of 480 psi for half-inch tubing at the same temperature. Rovanco publishes the same design rating, 160 psi at 73.4 degrees Fahrenheit, and does not publish a burst figure; Wavin publishes the design rating and the same burst table.

So the 50 psi recommendation is not about the tube. It is about everything attached to it: the fittings, the city water inlet, the check valve, the water heater connections and the appliance inlets. A system can hold 160 psi in the straight runs and still lose a fitting, because the tube rating says nothing about the parts screwed onto its ends.

What a regulator cannot do

Jabsco's specification settles the most common misunderstanding in one line. Its regulator acts on pressures from 46 to 125 psi, and pressures below 46 psi "will pass through unregulated." A regulator is a restriction with a set point. Below that set point it is not doing anything, and it has no mechanism to add pressure.

The practical consequence: if the water is weak at the tap, the regulator is not the cause and replacing it will not help. Look at the supply, the hose, the filter and the inlet screen instead.

The regulator has a ceiling of its own

Camco rates its regulators to a maximum incoming pressure of about 125 psi, and states that above it performance may be reduced or the body damaged. A regulator is protection against the range a campground normally delivers, not a guarantee against any supply. A park known for extreme pressure is a reason to check with a gauge rather than to trust the regulator alone.

The city water inlet, and the check valve inside it

The inlet is where the hose connects, and it carries a check valve. Jabsco describes the backflow preventer as "federal and state required on RV's with water service hookup," so the valve is not an accessory. It is the reason water does not run back out of the inlet when the pump is running and no hose is connected.

Four failures account for most inlet trouble. The check valve leaks, so the fresh tank slowly fills while you are on city water, or water runs out of the inlet when the pump runs. The valve sticks shut, so no water enters at all. The inlet screen tears, letting grit into the check valve and the regulator. The cap is lost, and the inlet fills with road spray.

Gravity fill and city fill are two different paths

A gravity fill is a large open port, usually on the side of the coach, that fills the fresh tank by pouring. A city fill connects to the pressurized supply and can either run the coach directly or, through a diverter, fill the tank.

The city fill bypasses the pump. That is why a pump fault and a city water fault can look identical at the tap and why the two are worth separating before any part is replaced. If the tap is weak on city water and strong on the pump, the pump is fine and the problem is upstream of the inlet. If it is weak on both, the restriction is downstream of both.

Checking the supply

A pressure gauge on the spigot before the hose answers the question the regulator is there to answer. Camco sells a regulator with a color-coded gauge for exactly this, and the reading tells you whether the park is delivering within the range your system was built for or well above it.

What this does not cover

The pump side has its own guide: RV water pump won't prime covers the tank, the suction line and the strainer. This page is the city water side, which is a different system with a different fault path.

Sources

Every figure on this page comes from a document the maker publishes. These are the documents, so you can check any of them.

• Winnebago, RV water pressure regulator round-up, quoting the owner's manual recommendation of 50 psi maximum.
• Jabsco, water pressure regulator brochure, for the 46 to 125 psi range, the 45 psi output, the variance, the backflow preventer requirement and the unregulated-pass-through line. The brochure is not hosted on Jabsco's own domain because there is no maker-domain copy: jabsco.com does not resolve, and the brand's page under its parent company carries no product documents. This is the document itself, on the host that has it.
• Camco, Ask the Expert, for the preset and the 55 to 60 PSI figure.
• Camco's own product pages do not publish specification text, so the adjustable unit's 45 psi preset and its 60 psi ceiling are taken from a distributor's listing rather than from Camco. They are recorded here as such rather than attributed to the maker.
• Viega, PureFlow PEX technical data sheet, for the 160 psi design rating and the ASTM F876/F877 burst table.
• Rovanco, Rhinoflex PEX piping specification, for the same design rating.
• Blu Technology, pressure regulator product page, for the 45 PSI preset and the 40 to 60 PSI recommendation.

Related guides

RV water pump won't prime for the suction side. Winterize your plumbing for what freezing does to the same lines. RV water heater not heating for the appliance at the end of the run.