RV Plumbing Repair in Florida: Fresh, Gray and Black Water
Fresh, gray or black? Place the fault first. Mobile RV plumbing diagnosis and repair for pumps, tanks, lines and leaks across Florida. Call 888-759-1438.
An RV has three separate water systems, and most plumbing calls are misdescribed because the owner has attributed a symptom to the wrong one. Fresh water is the only pressurized system, fed by a 12 volt pump or a city water hose. Gray carries sink and shower drainage, black carries toilet waste, and both empty by gravity. Place the fault in one of the three before naming a part.
What we handle in this category
Water heater tank, anode + element
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Truma AquaGo tankless service
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12V water pump replacement
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Black tank sensors + flush system
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Gray tank valve + cable
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PEX line + fitting repair
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Toilet flange + ball seal
See what this involves →Fresh, Gray and Black: The Three Systems Owners Conflate
An RV carries three water systems that share almost nothing but a bathroom wall. Fresh water is potable, it lives in the white tank, and it is the only one of the three under pressure, supplied either by a 12 volt demand pump or by a hose at the city water inlet. Gray water is what leaves the galley sink and the shower, held in its own tank and released through a gravity dump valve. Black water is toilet waste, dropped through a 3 inch floor flange into a third tank and emptied the same way. Nothing pressurizes gray or black, which is why a symptom that appears only while the coach is under pressure cannot belong to either of them. So before anyone names a part, place the fault. Is this a supply problem, a drainage problem or a holding problem? Almost every misdiagnosis in this category starts with that question skipped.
City Water or the Pump: The Test That Localizes a Fault
The most useful diagnostic in RV plumbing costs nothing. Run the fixture twice, once on the 12 volt pump with the hose disconnected, then once on city water with the pump switched off. A fault that shows on one supply and not the other has already told you which half of the fresh system it lives in. The two supplies are not equivalent. A pump governs its own pressure through a switch, and a Pentair SHURFLO Revolution 4008 shuts off at 55 psi and restarts at 40 psi, so the coach never sees more than the pump can make. A city hose delivers whatever the park delivers, steady and unregulated, sitting on every joint for as long as it is connected. A leak that appears only on city water is therefore a pressure story, a fixture that fails only on the pump is a suction, strainer or tank story, and a fresh tank that fills while you are on city water points at the pump one-way check valve or a bypass valve left open.
Triage by Symptom, and Which Repair It Points At
Eight complaints cover most of these calls, and each narrows to a system before it narrows to a part. No water at any tap is a supply question: an empty fresh tank, a pump with no power, or a valve nobody opened. Water at some taps and not others is a branch, a blockage or an open bypass rather than a pump. A pump that runs and never cuts out is losing pressure somewhere, while a pump that cycles with every tap shut is reporting a leak, trapped air or a dead accumulator. No hot water splits by fuel: dead on electric alone is the element side, dead on both is the tank or the appliance. Water under the coach earns a pressure decay test before anything gets cut open. A smell over a dry floor is a seal rather than a tank. Tank readings that never move are sensors rather than capacity.
What You Can Safely Check, and Where a Technician Starts
Owner checks are the ones that cannot flood, burn or electrocute anybody. Confirm the pump switch and the panel breaker, put a flashlight on the city water inlet and the wet bay floor, read the tank monitor after a verified dump, look at whether the water heater bypass valves are still in the winterize position, and time a quart jug at the weak fixture to measure flow. All of that is free, and it narrows the job before anyone arrives. The boundary is pressure, heat, gas and access. Cutting a coroplast underbelly, opening a hot water tank, working the LP side of an appliance, condemning a pump or pulling a toilet off a wet deck are technician work, because each one turns a small repair into a large one when it goes wrong. Our technicians start with those same free checks, then move to a gauge. The service call covers the trip out and the first hour on site, and anything past that is quoted and approved before work continues.
Why Florida Moves the Schedule and the Pressure
Most coaches here never get winterized, which removes the annual reset a northern rig gets by default. A system that stays warm and wet all year is one where biofilm and odor build with no freeze to interrupt them, so sanitizing becomes a calendar item instead of a spring ritual. Scale is the second tax. Much of the state draws from a limestone aquifer, and dissolved calcium settles onto valve seats, heat exchangers and tank walls. Pressure is the third. Park supply varies enough between sites that a regulator is not optional, and the ceiling belongs to the lowest-rated appliance in the coach rather than to one number: Truma lists a maximum water supply pressure of 65 psi for the AquaGo, while a Dometic 310 toilet is specified for 30 to 100 psi static. Set the regulator for the weakest link and every fixture stays inside its own range.
Sources
Every figure on this page comes from a manufacturer document or a standards body, not from another repair site. Here is where each one comes from.
- Pentair SHURFLO Revolution 4008 series RV fresh water pump, product technical data sheetThe pump side of the city-water-versus-pump test: the 4008 controls the coach at a 55 PSI shut-off and a 40 PSI re-start, carries a one-way check valve that prevents reverse flow, and is rated for a maximum inlet pressure of 30 PSI. That fixed switch band is why a fault that appears only on an unregulated city hookup cannot be reproduced on pump water.
- Truma AquaGo comfort instant water heater, technical dataThe lowest appliance ceiling used in the regulator argument: Truma lists a maximum water supply pressure of 65 psi for the AquaGo, alongside its 20,000 to 60,000 BTU/h modulating input and the approximately 0.4 gallons per minute of flow needed before the burner lights.
- Dometic Model 310 gravity-flush toilet instruction manualThat the toilet is fed from the pressurized fresh side but discharges by gravity: the manual specifies a water supply of 0.5 in. NPT at 30-100 PSI static with 2.0 gpm minimum flow, and a discharge through a floor flange of 3 in. inside diameter. The 30-100 PSI window is the wide appliance rating contrasted against the AquaGo ceiling.
- Suburban (Airxcel) Tank Water Heaters Operation and Maintenance Guide, part 206244That the water heater sits inside the fresh system behind a bypass kit, and the scheduled-work point for a coach that is never winterized: Suburban instructs owners to drain water from the tank whenever the RV is not being used and to avoid extended non-use with water in the tank, and recommends anode replacement once consumption or weight loss exceeds 75 percent.
Related systems
Where we work
What this usually costs
| Item | Price | What it covers |
|---|---|---|
| Service call | $299 | Includes the trip out to your RV and the first hour on site |
| Work past the first hour | Quoted after diagnosis | We tell you what it will take before we carry on |
| Parts | Quoted per job | Special-order parts may need a deposit before we order them |
| Written estimate | No charge | You approve the estimate before any work starts |
The service call covers the trip out to your RV and the first hour on site. Anything beyond that depends on what we find, and we quote it and get your approval before carrying on.
The price ranges on this page come from our own recent jobs across Florida, not from an industry average. What you pay depends on the rig, the parts it needs and what we find on site, so we give you a written estimate before any work begins and you approve it first.
Frequently asked questions
How do I tell whether my problem is fresh, gray or black water?
Ask what the water was doing when it failed. If it was under pressure and headed toward a tap, an appliance or the toilet valve, it is fresh. If it was leaving a galley sink or a shower drain, it is gray. If it involves the toilet, an odor or a tank reading, it is black. Fresh is the only pressurized system of the three, so anything that changes when you switch the pump off belongs to it.
Should I run on city water or on the pump when I am parked for a season?
Either works, but a long stay on city water means every joint in the coach holds park pressure day and night, including while nobody is inside. Use a water pressure regulator, and set it for the lowest-rated appliance you own rather than the highest. Truma rates the AquaGo for a maximum water supply pressure of 65 psi, which is under what some hookups deliver.
Why does my leak only show up when I connect the campground hose?
Because the pump cannot reproduce that pressure. A SHURFLO Revolution 4008 stops at 55 psi and drops back in at 40 psi, so a joint that weeps above the pump band stays dry on pump water and gives a clean test. Hook the same coach to an unregulated inlet and that joint is loaded continuously. Testing on both supplies is what separates a bad fitting from a pressure problem.
Do I need to winterize an RV that stays in Florida?
Usually not for freeze protection, since a hard freeze is mostly a north Florida and Panhandle concern. What still matters are the parts of the job about water sitting still: draining the water heater whenever the coach is not in use, which Suburban instructs directly, and sanitizing the fresh system on a schedule. A rig heading north for the summer is a different case and does need the full procedure.
What should I check before calling out a technician?
Four things, and none of them needs a tool. Confirm the fresh tank holds water and the pump switch is on, put a light on the wet bay and the underbelly seam, check that the water heater bypass valves are not still set to winterize, and note whether the fault appears on the pump, on city water or on both. That last answer usually decides how the visit runs.