Skip to content
Most RV repair bills aren't caused by bad luck. Habits cause them. Owners repeat actions without realizing the damage. Here are 11 common, costly mistakes. They are from professional RV technicians. These technicians see the consequences firsthand. Learn how to avoid them.
1. Leaving Your Black Tank Valve Open at Full Hookup Sites
The logic seems reasonable at first. Why not leave the valve open when connected to sewer? But liquids drain freely. Solid waste has nothing to carry it along. It accumulates and dries out. This creates what RVers call a pyramid. This hardened mass often needs professional service.
The fix: Keep the valve closed. Let the tank fill to at least two-thirds before dumping. The liquid volume creates the flow needed to clear solids completely.
2. Replacing Your Anode Rod Too Early
Every spring, owners post photos of corroded anode rods warning others to replace them immediately. In most cases, the rod is doing exactly what it's supposed to.
An anode rod is sacrificial, it corrodes so your steel water heater tank doesn't. Corrosion means it's working, not failing. Only replace it when the material around the core is almost entirely depleted. Replacing on a fixed annual schedule is an unnecessary cost with no benefit.
Note: Atwood water heaters have aluminium tanks and use a plastic drain plug, no anode rod needed. If yours has a plastic plug, leave it alone.
3. Drinking Unfiltered Water From Your RV's Fresh Water System
Sanitize your water tank and lines often. Otherwise, bacteria builds up over time. This is a genuine health risk for infrequent campers. Systems sit stagnant between trips. The connection to illness isn't always obvious.
If you're not on a rigorous sanitisation schedule, filter your drinking water or use bottled water while camping.
4. Not Understanding Your Thermostat's Fan Setting
This mistake regularly results in unnecessary diagnostic fees. The scenario: an owner turns on the furnace and the fan starts running. They assume something is wrong with the AC and bring the RV in for service.
Here's what happens: the thermostat is set to Fan. The blower runs continuously. This occurs whenever heating or cooling is active. Switch it to Auto instead. The fan only runs when the furnace heats. No repair is needed for this.
5. Using Under-Slide Jack Supports
Under-slide supports are sold as a way to stabilize extended slide-outs. RV technicians consistently identify them as a source of preventable damage.
A slide's position is relative to the RV itself. Fixing a support anchors one point. But the RV keeps moving. It settles, rocks in wind, or shifts on soft ground. This pushes up on one part of the slide. The structure around it has moved. This distorts geometry and stresses seals. It makes the slide difficult to retract.
Rack and pinion slides rely on gravity to engage their seals. Pushing up from underneath disrupts this. Don't use them.
6. Strapping Accessories to Your Rear Ladder
RV fixed rear ladders are designed for one condition: a stationary RV with someone climbing straight up. They are not built for highway travel.
An object that normally weighs 20 lbs can exert forces of 60–100 lbs as G-forces multiply over bumps and movement. Repeated stress works fasteners loose, often pulling through the rear wall and creating water entry points. RV technicians see this regularly, owners who bought legitimate accessories and ended up with self-inflicted leak repairs. The liability doesn't land on the seller.
7. Not Setting Your Brake Controller Correctly
Brake controllers have an adjustable gain setting. The factory default is rarely correct. It's for your specific vehicle and trailer. A low setting means poor trailer braking. This is under hard braking. It's a genuine safety issue, not just an inconvenience.
Before your first tow, understand how the gain adjustment works and set it for your trailer weight. If the dealership didn't explain this at purchase, find out before you drive anywhere.
8. Using the Wrong Hose With a Tankless Water Heater
Expandable collapsible hoses are convenient to use. But they cause intermittent tankless water heater failures. This is one of the hardest problems to diagnose. It also cannot be replicated at a service center.
Tankless heaters require minimum water flow to operate. Expandable hoses constantly try to contract back to their resting state, restricting flow. When pressure drops slightly after initial use, the hose restricts enough that the heater cuts out unexpectedly.
The fix: Use a standard blue drinking water hose for your city water connection. Keep expandable hoses for campsite cleanup only.
9. Using the Blowout Method to Winterise a Tankless Water Heater
The air blowout method works well for most of an RV's water system. Tankless heaters are the exception.
The heat exchanger has narrow internal passages that a straight air blowout doesn't reliably clear. Trapped water freezes, expands, and cracks the exchanger, an expensive repair. Use antifreeze when winterising a tankless unit, even if you blowout everything else. The cost difference is negligible compared to a cracked heat exchanger.
10. Forgetting the Exterior Shower When Winterising and De-Winterising: Common RV Mistakes
The outside shower is often missed. This happens in both processes. It's out of sight. This occurs when you work through the interior checklist.
When winterising, water left in the exterior shower line and head freezes and cracks. Depending on the line routing, this can push water into wall cavities where damage isn't visible until it's extensive. When de-winterising, antifreeze left in the line back-bleeds into your water supply. Non-toxic, but certain types leave a smell that's difficult to get rid of.
Add the exterior shower explicitly to both checklists. It takes thirty seconds.
11. Upgrading to Lithium Batteries Without a DC to DC Charger
Swapping lead-acid for lithium can be problematic. Not addressing the charging system is damaging. It can damage your tow vehicle's alternator. Lithium and lead-acid batteries have different charge characteristics. A standard alternator may connect to a lithium bank. The system can attempt to draw excess current. This exceeds the alternator's continuous design limits.
The correct solution is a DC to DC charger. It goes between the tow vehicle's electrical system. It connects to the RV battery bank. There are isolated and non-isolated versions. The correct type depends on your RV. Is it a towable, or a motorized unit? If a technician ignores this, find another technician.
Frequently Asked Questions
How often should I replace my RV anode rod?
Only when the sacrificial material around the core is nearly fully depleted — not on a fixed annual schedule. Inspect it each season and reinstall it if substantial material remains.
Is it safe to drink water from my RV's fresh water system?
It depends on how frequently you sanitise the system. Infrequent campers who don't sanitise between trips should filter drinking water or use bottled water as a precaution.
What hose should I use for my RV's city water connection?
Use a standard blue drinking water hose. Avoid expandable hoses as your primary connection. They restrict flow enough. This causes intermittent heating failures. These failures are difficult to diagnose.
The Bottom Line
Most expensive RV repairs have a paper trail. Small decisions led to them. A valve was left open. A support was in the wrong place. A hose restricted flow just enough. None of these mistakes are obvious. Someone must explain why they matter. That's why they repeat consistently. It happens across all owner experience levels.
Owners who keep RVs from service centers are not those with new rigs. They don't have the most expensive setups either. They understand how their systems actually work. They also know what not to do to them. Most of the time, that knowledge costs nothing. Only the time to find it is the cost.
