RV Plumbing, Tank and Water System Repair

By holding pressure and isolating sections. Running the pump and looking for drips finds only the leaks that have already soaked through something, which by definition means the damage is already done.

The method is to charge the system, shut the pump off and watch the pressure. A system that holds is tight. A system that bleeds down has a leak, and the rate tells you roughly how big. Then sections get isolated with valves or with temporary caps, and the section that keeps dropping is the section with the fault. On a coach with runs buried behind wall panels, that isolation step saves opening walls that did not need opening.

Where the leak sits matters as much as that it exists. Most modern coaches use PEX with crimp or clamp fittings, and PEX rarely fails in the middle of a run. It fails at fittings, and the fittings fail because a crimp was made slightly off-square at the factory or because a fitting was overtightened. A crimp that was marginal holds for years and then weeps, which is why a thorough fresh water job checks every accessible fitting rather than only the one that is visibly wet.

Older units may still carry grey polybutylene, which becomes brittle with age and chlorine exposure and fails without warning. Where that is found, replacement of the affected runs is usually recommended rather than repair.

Because the sensors are almost never broken. They are probes through the tank wall that measure conductivity between contact points, and the reason they read full when the tank is empty is that residue is bridging them.

On a black tank, solids and tissue coat the probes. On a gray tank, soap scum and grease do the same thing. Either way the probe sees continuity and reports liquid at that level. Replacing the sensors without cleaning the tank produces a tank that reads wrong again within weeks.

Proper treatment is mechanical: a tank wand or a rotating cleaner to break the residue off the walls and off the probes, followed by a full flush, followed by re-verification of the readings. Where the tank has been neglected for years and the buildup has hardened, the tank may need to come out.

The other tank issue is cracks. They come from three sources: freezing, which splits a full tank; road impact, on tanks mounted low without a skid; and mounting straps that loosened and let a full tank hang on its own weight, which cracks it at the mounting boss. Repair versus replacement depends on where the crack sits, because a crack at a fitting boss or at a mounting point rarely holds a repair. Black and gray tank repair and replacement runs $750 to $8,500 across 5 to 35 hours, and the labor spread is entirely about what has to come apart to reach the tank on a given floorplan.

Gate valves are the third item. They fail from debris on the seat and from being left open, which lets solids settle against the blade. A valve that will not seal is replaced, and the fitting flange behind it is inspected while the access is open.

Four types show up regularly and they behave nothing alike.

Tank type, propane and electric

Six or ten gallon tanks from Suburban and Atwood dominate older and mid-market units. Suburban tanks are steel with an anode rod that sacrifices itself to protect the tank; that rod is a consumable and a tank whose rod was never changed is a tank that will rust through. Atwood tanks are aluminum clad and do not use an anode.

Tankless propane

On demand units that fire when flow is detected. They deliver unlimited hot water and they are sensitive to flow rate, so a low-flow fixture can fail to trigger the burner. Altitude and inlet water temperature both affect output.

Truma combination units

Combined water and space heating in a single appliance, common on newer European-influenced builds and van conversions. Service is specific to the unit and diagnosis is done through its control panel.

AquaHot and hydronic systems

A diesel burner and an electric element heat a glycol loop, which then feeds domestic hot water through a heat exchanger and space heat through zone exchangers. A fault can be in the burner, the circulation pump, a zone valve, the exchanger or the control board. Hydronic service runs $750 to $8,500 across 3 to 35 hours.

Water heater service across all types runs $350 to $4,500 across 1 to 18 hours. Full bands sit on the price sheet.

• Fresh Water System Repair: lines, fittings, city water inlet, pressure regulation and winterization, $285 to $4,500.
• Waste Water Black and Gray Tank Repair: tanks, sensors, gate valves and vent stacks, $750 to $8,500.
• Water Heater Repair and Replacement: tank, tankless, Truma and hydronic, $350 to $4,500.
• Toilet, Sink and Shower Repair: toilet replacement at $300 to $1,500, shower and pan replacement at $750 to $5,500, faucets at $200 to $800.
• Pump and Valve Repair: fresh water pumps, macerator and sewer pumps at $400 to $1,800, check valves and diverters.

Sibling lines under mechanical and systems services are electrical repair, generator repair and appliance repair. Plumbing crosses into interior remodeling constantly, because a shower pan replacement is a wall panel job and a tank replacement is often a floor job.

It removes or protects water anywhere it can freeze. In Southern California most owners never need it for local storage, and then they take the coach to the mountains or to a winter rally and find out that a single overnight below freezing splits a fitting.

Two methods. Blowing out the lines with compressed air at a regulated low pressure clears standing water from the runs and from the fixtures. Pumping propylene glycol antifreeze through the system displaces water with fluid that will not expand when frozen. The second is more thorough because it also protects traps and the water heater bypass loop.

The steps that get missed are the ones that cause the damage: the water heater has to be drained and bypassed, not filled with antifreeze; the low point drains have to be opened; the fresh tank has to be drained; the toilet valve and the outside shower have to be cycled with antifreeze through them; and the water filter cartridge should come out.

Winterization and de-winterization runs $250 to $750 across 1 to 4 hours. It is cheap insurance relative to a split PEX manifold behind a wall panel, and de-winterization in spring is the right moment to pressure test the system before the first trip.