Your RV water system is simple in concept and surprisingly easy to misdiagnose. Two ways to get pressure, a handful of valves most owners don't know exist, and one detail about faucet screens that solves more "water problems" than people expect. This lesson covers all of it in plain English.
This is the starting point for understanding your entire water system — and the thing that makes most water problems easier to diagnose once you get it.
Your RV has two completely separate ways to pressurize water. One uses your onboard pump and your fresh water tank. The other uses the campground's water supply connected directly to your RV. They do not run at the same time — and problems on one side don't usually affect the other.
Your onboard pump pulls water from the fresh water tank and pressurizes the lines. It cycles on and off to maintain pressure — you'll hear it kick on briefly when you open a faucet.
If the pump runs constantly without shutting off, or cycles rapidly without a faucet open, the system has a leak somewhere. The pump is telling you — even if you can't see it yet.
The pump switch must be ON for this to work. When switching to city water, turning the pump off is good practice — it prevents the pump from running if a line loses city water pressure unexpectedly.
City water connects directly to your RV's water lines through the inlet on the outside of the rig. The campground's pressure pushes water through the system — no pump required.
Unlike the pump, city water won't tell you about a leak by cycling. It'll show up physically first — wet carpet, water under a cabinet, or a dripping connection. By the time you notice, it's already been running.
A pressure regulator between the campground supply and your RV inlet is not optional — it's the most important component in the system. Campground pressure varies wildly. Too much pressure stresses every fitting, hose, and valve in your rig.
When a water problem happens, the first question is always: which source are you using? Pump pressure and city water fail in completely different ways. Knowing which one you're on cuts your diagnosis time in half before you check anything else.
If you're not using a pressure regulator every time you connect to city water, you're taking a real risk with your plumbing. Campground water pressure is inconsistent — some sites run higher than residential pressure, and RV fittings, connections, and hoses are not built for that.
A failed fitting under high city water pressure doesn't just drip. It runs. And unlike a pump that cycles and tells you something is wrong, city water just keeps flowing until you notice the damage.
A pressure regulator threads onto your city water hose before it connects to the RV inlet. It limits incoming pressure to a safe range — typically around 40–50 PSI. This is cheap insurance for your entire water system.
I've seen significant water damage inside RVs from a single night on high-pressure city water without a regulator. A fitting lets go behind a wall or under a cabinet and by morning the damage is done. A quality inline regulator costs very little compared to what it protects.
The city water inlet has a small screen inside it to catch debris from the hose connection. That screen can get clogged and restrict flow. If city water pressure seems low, check that screen before assuming a regulator or campground supply problem — it's easy to miss and easy to clean.
The pump is simple in concept. It pulls water from the fresh tank, pressurizes the lines, and shuts off when pressure builds. When it works, you barely notice it. When something goes wrong, it usually tells you through its behavior before anything else fails.
I've had owners come in completely confused about why their holding tank keeps filling. They've checked everything obvious. The pump's internal check valve failing and allowing back-feed is almost never on anyone's list — but it happens. If your tanks are mysteriously filling and you can't figure out why, that's where I'd look.
Your RV water system has more valves than most owners realize. Some are obvious. Some are hidden. And some get left in the wrong position after winterization — which causes problems months later that look like something completely different.
The most important rule for any valve in your system:
Handle pointing with the line = open. Handle pointing across the line = closed.
This applies to almost every quarter-turn valve in your RV water system. When in doubt, look at which way the handle is pointing relative to the pipe it's on.
Here's the fix that most people skip and then kick themselves for later: if only one faucet or fixture suddenly has low flow or no flow, check the aerator screen before anything else.
Every faucet has a small screen — the aerator — at the end of the spout. It catches debris that travels through the water lines. After de-winterizing, after flushing antifreeze, after any work on the water system, debris gets dislodged and can clog that screen completely.
The clue is that everything else works fine. Full pressure at other fixtures, but one faucet is barely trickling. That pattern almost always points to a clogged aerator — not a plumbing problem, not a valve, not a pump issue.
The showerhead has a screen too — and so does the connection where the supply hose meets the showerhead. If shower pressure drops suddenly, start there before assuming a pump or pressure problem.
Winterization gets more complicated every year as RV systems get more complex. But the core principles haven't changed — and understanding them makes the process make sense regardless of what system you have.
The goal is simple: get every drop of water out of every line, valve, fitting, and fixture before freezing temperatures can reach them. Water expands when it freezes. Fittings, tanks, pump housings, and water heater tanks don't. The damage that results is expensive and completely preventable.
Most RVs are winterized using RV antifreeze — a non-toxic pink antifreeze that's safe for drinking water systems. The process pumps antifreeze through every line until pink fluid comes out of every fixture. The antifreeze doesn't freeze solid — it protects the lines and fixtures through cold temperatures.
Never use automotive antifreeze in an RV water system. It is toxic. RV-specific antifreeze — the pink kind — is the only type safe for this use.
The water heater tank holds 6–10 gallons depending on the unit. Without a bypass, that entire tank fills with antifreeze during winterization — which is wasteful and unnecessary. The bypass valves route antifreeze around the tank so the lines get protected without filling the heater.
In spring, those bypass valves need to be returned to normal position before filling the system. A water heater left in bypass is one of the most common spring complaints — the owner fills the system, pressure comes up, everything seems fine, but there's no hot water. The heater tank never filled.
If your RV has an inline water filter, remove or bypass the cartridge before winterizing. Antifreeze damages the filter media — and a saturated filter will also need to be flushed completely before the water is safe to drink in spring. Replace the cartridge when you de-winterize.
RVs with on-demand or tankless water heaters — Girard, Truma Combi, Aqua-Hot — have their own specific winterization procedures that differ from standard tank heaters. If your rig has one of these systems, follow the manufacturer's procedure for that unit specifically. The general bypass approach does not apply the same way.
The free section gives you the foundation. Pro members get the step-by-step field procedures that help you actually find problems and fix them.
Join Pro — Get Full Access