RV water pump problems: no pressure, constant cycling, and what each fix costs

RV water systems fail in a small number of predictable ways, and the useful first step is figuring out which side of the system has the problem. That takes about ten minutes and it is the difference between a $250 to $500 pump replacement and a fitting you can tighten by hand.

Check this first (ten minutes)

Is there water in the fresh tank? Tank sensors lie constantly, particularly on a rig that sat through the summer. Do not trust the panel.
Compare city water to pump. Hook up to the city inlet and open a tap. Good pressure on city and nothing on the pump narrows the fault to the tank, the strainer, the pump, or its check valve. The reverse narrows it to the city inlet side.
Look at the pump’s inlet strainer. Clear plastic housing, usually right at the pump. Debris, a slimy film of growth from a tank that sat with water in it all summer, or a collapsed screen in there will starve the pump. This is the single most common fix.
Listen to the pump. Running smoothly but no water means it is not picking up: air leak on the suction side, clogged strainer, or a dry tank. Running rough or loud usually means air or a failing pump.
Open a tap and let it run. A pump that eventually catches and delivers was airlocked. This is normal after filling an empty tank and it is not a fault.
Walk the rig with a flashlight. Look under the sink cabinets, at the water heater connections, behind the toilet, and at the low point drains. A leak that is escaping to the outside will show as a damp underbelly or a drip line on the ground. A leak that is staying inside shows up first as a musty cabinet, so use your nose as well.

What is usually wrong

What you observe	Likely cause	Fix and cost
Pump runs, no water at all	Empty tank, clogged strainer, or a suction air leak	Often under $250
Pump cycles rapidly with taps closed	Small leak, failed check valve, or toilet valve seeping	$150 to $400
Weak pressure everywhere	Failing pump, partly closed valve, or a blocked filter	Pump $250 to $500
Weak pressure at one fixture only	Aerator or that fixture’s cartridge	Usually under $200
Pump will not run at all	Fuse, switch, corroded wiring, or a dead pump	$150 to $500
Water in the underbelly or a drip on the ground	Line or fitting failure	Plumbing repair $200 to $800
Fine when on city water, nothing on the pump	Pump side	Pump or strainer
Fine on the pump, nothing on city water	City inlet, check valve, or regulator	Usually under $250
Water tastes or smells off after summer	Tank and lines need sanitizing	Sanitize and flush, often under $200

Ranges come from the pricing page, plus the $75 to $150 trip fee and $125 to $190 hourly labor.

The Florida angle

Water left standing. The winter season here runs November through April, and a rig that sits from May to October with water in the fresh tank and the lines has spent that time at 80 to 90 degrees with the air outside at a dew point in the 70s. Whatever was in the water grows. The classic November call is a pump that runs but delivers nothing because the strainer is coated in slime, or water that smells like a pond. Draining the tank before you leave and sanitizing the system when you return solves most of it, and we do the sanitizing as part of an arrival check.

Corrosion on the electrical side. The pump’s own switch, its fuse holder, and the crimp connections at the pump are all exposed to months of saturated air. A pump that “died” is sometimes a green connector. We check the 12V side before we condemn the pump.

Wet cabinets. A dry climate lets a small leak evaporate. This one does not. A fitting weeping behind the shower wall keeps the cabinet wet around the clock, and mold follows within days. That is the practical reason a pump that cycles with the taps closed should not be ignored for a season, even though the leak itself might be a few drops an hour.

Pressure at the pedestal. Some parks deliver higher city pressure than an RV system is designed for, and pressure surges when a park’s supply cycles are real. A regulator at the inlet is cheap insurance and prevents the kind of blowout that empties a fresh tank into a cabinet while you are at dinner.

Storms and the pedestal. After a thunderstorm, a pump that will not run at all is often a tripped GFCI or breaker on the 12V converter side rather than the pump. Check that before anything else.

When you cannot find the leak

Water tracks. A leak at a fitting behind the water heater can show up on the floor eight feet away, and a leak inside the underbelly may not show at all until the coroplast bellies down and starts to smell. If the pump cycles and nothing is visible, a pressure test is a faster and cheaper answer than pulling panels one at a time, and that is part of what the diagnosis visit is for.

What to expect on the call

Tell us whether city water works, whether the pump runs, what the strainer looks like, and whether you have seen or smelled any water where it should not be. Most pump calls are diagnosed on the phone to within two possibilities. We work on site across Zephyrhills, Dade City, San Antonio, Wesley Chapel, and Land O’ Lakes, and if the problem turns out to be the water heater rather than the pump, that page covers it.

Frequently Asked Questions

My RV water pump runs constantly and never builds pressure. Why?

The pump cannot reach its cutoff pressure, which means either it is not moving water, or water is escaping somewhere. Air in the line, a strainer clogged with debris, a failed check valve, a tank that is empty, or a leak you have not found yet are the usual five.

What does an RV water pump replacement cost?

$250 to $500 including the pump, fittings, and labor. Strainer cleanings, check valves, and loose fittings are much cheaper, often just the trip fee plus part of an hour, which is why the diagnosis comes first.

The pump cycles on and off every few seconds even with the taps closed. Is that bad?

It means pressure is bleeding off somewhere: a small leak, a failed check valve, a toilet valve seeping, or a water heater bypass valve partly open. It is also hard on the pump. Worth finding, and usually cheap when you do. In this humidity a slow leak inside a cabinet also grows mold fast, which is the better reason to chase it.

I have city water pressure but nothing from the pump, or the reverse. What does that mean?

It tells you a lot. Good city pressure and nothing on the pump means the problem is on the pump side: tank, strainer, pump, or its check valve. Good pump pressure and nothing on city water means the city inlet, its check valve, or the regulator.