Measuring Water Pressure in a Motorhome

The Short Answer

For most owners, the practical method is a screw-on gauge at the hose connection. Attach it to the campground spigot on its own to read the raw supply. Then attach it downstream of your pressure regulator to confirm what actually reaches the motorhome. The gauge tells you whether the regulator is working and whether low or high pressure explains a problem inside the coach. Testing the onboard pump is a separate job, because the gauge has to sit in the pump's output path rather than at the city water inlet.

There is no single correct pressure for every motorhome. A target range of roughly 40 to 60 psi is widely cited for RV plumbing, and many fixed regulators are set somewhere within it. Your coach's own documentation, and the ratings of its fittings, faucets and water heater, take priority over any general figure.

Two Water Systems, Two Kinds of Pressure

A motorhome usually has two ways of getting water to the taps, and pressure behaves differently in each.

City water (shore supply): an external water supply connected by hose to the coach's city water inlet. Pressure comes from the campground or municipal system and can be higher than the plumbing is designed for, which is why a regulator is normally used. Onboard pump: a 12-volt pump draws from the fresh water tank and pressurizes the lines. A pressure switch turns the pump on when pressure falls and off when it reaches the switch's set point. Tank capacity determines how long you can run before refilling. It does not set the pressure; the pump and its switch do.

Most city water inlets include a check valve that stops pump-pressurized water from flowing back out through the inlet. As a result, a gauge fitted at the inlet generally will not show pump pressure.

Types of Water Pressure Gauge Used on Motorhomes

Gauge type | Where it goes | What it tells you | Typical use; Inline hose gauge | Threads onto a spigot or between hose and regulator | Static supply pressure, or regulated pressure if placed after the regulator | Quick checks at each new site; Regulator with built-in gauge | Combined unit at the spigot or hose end | Output pressure of the regulator | Everyday campground hookup; Adjustable regulator with gauge | At the spigot, with a dial or screw adjustment | Output pressure as you set it | Owners who want to choose their own target pressure; Permanently installed gauge | Plumbed into a tee in the coach's supply line | Pressure inside the system, including from the pump if placed on the pump side | Ongoing monitoring and diagnosis

In the US, hose-mounted gauges and regulators normally use standard garden hose thread, so they fit common spigots and drinking-water hoses without adapters. Permanently installed gauges depend on the coach's pipe type and fitting sizes, so check those before buying parts.

How to Measure Campground Water Pressure

1) Thread the gauge directly onto the spigot, with nothing else attached, and open the tap fully. The reading is the site's static supply pressure. 2) Close the tap and fit your regulator, then the gauge, in that order. Open the tap again. This reading is the regulator's output. 3) Connect the hose and regulator to the motorhome as normal. If you use an inline gauge, it can stay between the regulator and the hose so you can glance at it. 4) Open a faucet inside the coach and watch the gauge. A drop under flow is normal. A large drop can point to a restriction, a long or narrow hose, a clogged filter, or a weak supply.

A static reading, taken with no water flowing, shows the maximum pressure the plumbing will see. That is the number that matters for protecting fittings. A dynamic reading, taken with water flowing, is closer to what you feel at the shower head.

How to Check Onboard Pump Pressure

To see what the pump delivers, the gauge must be on the pressurized side of the pump.

A permanently installed gauge on a tee in the pump's output line gives a continuous reading. Some owners use a hose-thread outlet, such as an exterior shower or utility connection, with a gauge attached, because it is fed by the same pressurized lines. With the pump running and all taps closed, the gauge should climb and then hold once the pump switches off. If the reading slowly falls and the pump cycles on by itself, there may be a leak or a pump check valve that is not sealing.

Pump set points vary by make and model. Compare your reading with the pump's own rating rather than with campground figures. Adjusting a pump's pressure switch, where that is possible at all, should follow the pump maker's guidance.

Pressure Is Not the Same as Flow Rate

Pressure is the force pushing the water. Flow rate is the volume delivered over time, usually given in gallons per minute. A gauge can read healthy pressure while flow at the tap is weak, for example when a filter cartridge is clogged, a faucet aerator is blocked, or a kinked or long hose restricts the line. The reverse can also happen: good flow at a high, unregulated pressure that puts stress on fittings. If water at the taps seems wrong, check both.

Filters and Pressure Drop

Any inline filter adds some resistance, and the drop grows as the cartridge loads up with sediment. When you choose a filter, look at its filter specification, including its pressure rating, rated flow and micron rating. A finer filter traps smaller particles but usually restricts flow more. Watching the gauge downstream of the filter over time gives you a practical cue for replacing the cartridge: if regulated pressure under flow keeps falling while the supply has not changed, the filter is the first thing to check.

Reading the Results

Supply well above your target: use a regulator, and confirm with the gauge that its output is where you want it. Regulated output higher than expected: the regulator may be faulty, set too high, or the wrong part for your needs. Low pressure at both the spigot and the coach: the site supply is likely weak. Switching to the onboard pump may give better results. Good pressure at the spigot but poor flow inside: look for restrictions in the hose, filter, inlet screen or faucet aerators. Pump pressure falls with all taps closed: suspect a leak or a pump check valve that is not holding.

Keeping Measurements Sanitary

Anything in the fresh water path should be suitable for drinking water. That includes gauges and regulators, typically made of lead-free brass or another potable-rated material, and hoses sold for drinking water use. Keep fresh water gear separate from anything used for waste tank rinsing, cap or bag hose ends when stored, and include the gauge and regulator in your routine fresh water system sanitation.

Bottom Line

An inexpensive water pressure gauge at the hose connection answers the most common question: is the pressure entering the motorhome within a safe, comfortable range? Measure the raw supply first, then the regulated output, and treat the onboard pump as a separate check that needs a gauge on its own side of the system. Read pressure alongside flow, account for filters, and use your coach's documentation as the final reference for acceptable limits.