rvfieldguide.com RV Field Guide
B1

Pre-Purchase Inspection

The exact walkthrough a professional RV inspector runs — in order, in 90 minutes. Frame, roof, plumbing, electrical, and appliances before you sign anything.

⏱ 90 min

A professional RV inspector charges $200–$400 and is worth every penny — but most buyers skip it entirely, especially on private-party purchases where there's no dealer to push back against. This checklist is the walkthrough a certified inspector runs: frame to roof, plumbing to electrical, appliances to tires. It won't replace a professional with a moisture meter, but it will catch the things that cost thousands to fix before you sign anything.

Water damage is the variable that separates a solid used trailer from an expensive mistake. It starts at the roof — every seam, every penetration, every vent — and works down. By the time it shows up as a soft floor or a stained ceiling, it's been there for a while. The three-part check is: press the screwdriver handle into the floor near doors and windows, look up at the ceiling for any yellowing, and get on the roof and feel for soft spots. These three steps alone will flag the trailers worth walking away from.

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A professional inspection costs $200–$400 and is worth every penny. But if you're standing in a seller's driveway — or just want to know what the inspector is looking at — this is the exact walkthrough they run. Work through it in order. Give yourself at least 90 minutes. Rushing this is how people buy someone else's problem.

Before You Go — Tools to Bring

  • Flashlight or headlampinspect under beds, in bays, inside cabinets
  • Flathead screwdriverpress handle (not point) into soft floor spots to test for rot
  • Digital tire pressure gauge
  • Spray bottle filled with soapy waterpropane leak test
  • Phone cameradocument everything, especially anything that needs negotiating
  • Multimeteroptional but useful for checking battery voltage

Schedule on a sunny day

Natural light makes water stains, delamination, and roof cracks dramatically easier to spot.

Section 1 — First Impressions & Exterior

Walk the entire rig slowly before touching anything. You're looking for the story the trailer tells before anyone starts selling it to you.

  • Overall levelnessdoes the trailer sit flat, or does it list to one side? (frame, axle, or spring issue)
  • Paint and decal conditionfading is cosmetic, but crazing or bubbling over fiberglass = delamination
  • Sidewall delamination: press gentlyfiberglass should feel solid, not spongy or wavy
  • Windows and doorsopen and close every one; check seals for cracking or gaps
  • Entry stepstest for stability; bent or wobbly steps indicate rough use
  • Storage bay doorsopen all of them; check latches and look for signs of moisture inside
  • Exterior caulk and sealant: anywhere two surfaces meet is a potential leak pointlook for cracks, gaps, or missing sections
  • Corner caps and trimcracked or loose corners let water in and are surprisingly expensive to replace

⚠ Dealbreaker Watch

Bubbling or rippled sidewalls are delamination — water has already gotten between the skin and the frame. Small patches can be repaired; large sections across a whole wall cannot be economically fixed.

Section 2 — Frame, Axle & Running Gear

Get low. This is where the most expensive surprises hide.

  • Frame railslook for rust (surface rust is normal; pitting, flaking, or holes are not)
  • Frame weldscheck for cracks at stress points near the hitch and axle mounts
  • Leaf springs: look for cracked, missing, or severely sagging leavesgrab and push down; it should rebound smoothly
  • Spring hangers and U-boltsshould be tight with no cracks or bends
  • Axlelook for bends or obvious damage (a bent axle causes uneven tire wear and handling issues)
  • Equalizer bars (tandem axles)wear here is normal but excessive slop means replacement time
  • Wheel bearingsspin each wheel by hand; it should turn smoothly with no grinding or wobble
  • Brakes (electric)have someone activate the brake controller in the tow vehicle; you should feel resistance at each wheel
  • Lug nutsvisual check for missing or cross-threaded nuts
  • Underbelly wraptorn or sagging = water or rodent damage inside the underbelly

⚠ Dealbreaker Watch

A bent frame or cracked welds at structural points are walk-away conditions. These are not repairable to original spec.

Section 3 — Tires & Wheels

Trailer tires fail more often than people expect — and almost always at highway speed.

  • Tire pressurecheck with gauge; note the correct spec from the door jamb sticker, not the tire sidewall
  • Tire age: find the DOT code on the sidewalllast four digits are week and year of manufacture (e.g., 2319 = 23rd week of 2019). Tires over 5–6 years old should be replaced regardless of tread depth
  • Tread depth: use a pennyLincoln's head disappearing into the tread means you're good; showing fully means replace
  • Sidewall conditionweb-like cracking = dry rot; bulges or bubbles = replace immediately
  • Rim conditionlook for cracks, bends, or excessive rust at the bead seat

Why Age Beats Looks

A trailer tire can look nearly new and still fail from UV and ozone degradation. Age is the real number — always check the DOT date. Sellers often don't know it and buyers almost never ask.

Section 4 — Roof & Seams

More RV damage comes from the roof than anywhere else. Water damage always starts here.

  • Get on the roof if possible (check the ladder is secure first; most RV roofs support one person)
  • Roof membraneEPDM rubber should be smooth with no tears, cuts, or punctures; TPO and fiberglass roofs should have no cracks
  • All seams and seals: run your finger along every seamaround vents, skylights, A/C unit, and the perimeter where roof meets sidewall
  • Soft spots on the roofwalk slowly and feel for any flex or give (normal roofs are firm)
  • A/C unitinspect mounting feet and the gasket seal underneath; a poorly sealed A/C is one of the most common water entry points
  • Roof ventsopen and close each one; check the seal and the crank mechanism
  • Antenna or solar panel mountsinspect all penetration seals

⚠ Dealbreaker Watch

Any soft spot on the roof means water has already penetrated the decking. If it's soft in one place, check directly below it inside — you'll almost certainly find staining or rot.

Section 5 — Interior: Floor, Walls & Ceiling

Water damage is the most expensive thing you can inherit. Every soft spot or stain has a history.

  • Walk the entire floor slowlyfeel for soft spots, flex, or spongy areas (especially near doors, windows, and the bathroom)
  • Press the screwdriver handle into suspicious soft spotsit should not sink in
  • Pull back any rugs or matslook at the subfloor for staining or discoloration underneath
  • Inside corners and window frames: look for staining, soft drywall, or bubbled wallpaperfirst places water damage shows up
  • Ceiling: look for yellowing, staining, or bulgingthese always indicate a roof or skylight leak above
  • Slide-out rooms (if present)extend fully, inspect the floor and seals on all four sides; close and re-open to confirm smooth operation
  • Cabinet interiorsopen every door and drawer; smell for mold; look for mouse droppings or evidence of pests

The Smell Test

Before you look at anything, close the door, stand quietly, and take a breath. Mustiness, mold, or a sharp ammonia smell (rodents) are flags worth paying attention to. You can fix a lot of things — you cannot fully un-mold a trailer.

Section 6 — Plumbing & Water System

  • Fresh water tank: ask when it was last sanitized; open the drain and smellmusty or sulfur smell indicates bacteria
  • Fill the fresh tank and run every faucetcheck hot and cold pressure, look under sinks for drips while the water runs
  • Water heaterturn on and let it heat; check the pressure relief valve and the area around the unit for water staining
  • Shower/tubrun the water and check for soft floor or wall panels around the surround
  • Toiletflush it; it should seal fully and the pedal mechanism should feel solid
  • Under-sink and under-bath plumbinglook for active drips, staining, or corroded fittings
  • Holding tanksask for the last dump date; if they're full, that's a red flag
  • Black and gray tank valvespull each one to confirm it moves freely and seals completely

Winter Bypass Confirmation

Ask the seller if the trailer was properly winterized each year. A single season of burst pipes can mean hidden plumbing damage throughout the rig. Signs: water stains with no obvious source, low pressure at specific fixtures.

Section 7 — Electrical System

  • Shore power hookupplug into 30A or 50A power if available and test every outlet with a phone charger or multimeter
  • Battery condition: check voltage12.6V+ is healthy; below 12V with nothing running indicates a weak battery
  • 12V DC systemtest interior lights, fans, water pump, and slide-out motors on battery only
  • Converter/chargerwhen plugged in, battery voltage should read 13.5–14V (charging); if not charging, the converter may be faulty
  • Breaker panellook for any breakers in the tripped position; ask about any that keep tripping
  • 7-pin connectorinspect pins for corrosion or bent contacts
  • Brake controller plug-in (if equipped)confirm trailer brakes activate when the controller is triggered

⚠ Dealbreaker Watch

Any signs of DIY electrical work — exposed splices, wire nuts, mixed wire gauges — should make you nervous. RV electrical fires are real and usually start at a bad connection.

Section 8 — Propane & Appliances

  • Propane tankscheck gauge levels; inspect the regulator and hose for cracking or brittleness
  • Leak check: with tanks on, spray all fittings and connections with soapy waterbubbles = active leak
  • Furnaceturn on and let it run for 5 minutes; confirm ignition and airflow from all vents
  • Water heater (propane mode)switch to LP and confirm it lights and heats
  • Stovelight all burners, confirm clean blue flame
  • Oventurn on and verify it reaches temp
  • Refrigeratortest on both electric and propane modes; it should reach below 40°F on each within a reasonable time
  • Microwave (if present)test with a glass of water
  • A/C unitrun on high fan and full cooling for at least 10 minutes; confirm cold air output

Why Test Both Modes on the Fridge

RV absorption refrigerators can fail in one mode while working fine in the other. A fridge that runs on electric but won't light on propane — or vice versa — is a repair job. Replacement absorption fridges are expensive.

Section 9 — Hitch & Tow Connection

  • Coupleropen and close the latch mechanism; it should snap firmly with no slop or wear
  • Coupler sizeconfirm it matches your tow vehicle's ball (1-7/8", 2", or 2-5/16")
  • Safety chain loopslook for cracks, deep rust, or bent links
  • Breakaway cable and switch: pull the cable pinthe switch should trigger (you can test with a multimeter across the terminals)
  • Tongue jackcrank up and down through full range; listen for grinding; confirm it holds load without drifting
  • Weight distribution receiver (if present)inspect for cracks at the mounting plate

Final Walk — Dealbreaker Summary

  • Structural delaminationlarge sections of wavy, bubbled sidewall
  • Soft floorany area that moves under a screwdriver handle
  • Roof soft spotsespecially combined with ceiling staining below
  • Bent or cracked frameat welds, hitch area, or axle mounts
  • Active propane leakbubbles found at any fitting
  • DIY electrical workexposed splices, junction boxes, mixed wire
  • Mold smellespecially in the bathroom, under beds, or in slide-out seals
  • Tires over 6 years oldfactor replacement cost into your offer ($150–$250/tire)
  • Non-functional appliancesprice parts and labor before agreeing to buy as-is

The Offer Rule

Every item that's wrong is a negotiating point, not a dealbreaker by itself. Get two things: a written list of everything you found, and a rough repair estimate. Then decide if the asking price — minus those repairs — is still a fair deal.

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Field Notes

Things worth knowing

01

Schedule the inspection on a sunny day. Natural light makes delamination, water staining, and roof cracks dramatically easier to spot than overcast or artificial light.

02

Bring a spray bottle of soapy water even if you don't think you'll need it. A propane leak that isn't caught at the seller's driveway becomes your problem the first night you're in a campsite.

03

If the seller won't let you run appliances, test water, or plug into power, walk away. A motivated seller with nothing to hide has no reason to restrict a standard inspection.

Common Questions

Frequently asked questions

What should I look for when buying a used RV trailer?

The three most expensive things to get wrong are water damage, frame damage, and bad tires. Water damage starts at the roof seams and shows up as soft floors, stained ceilings, and bubbled sidewalls. Frame damage usually shows at welds near the hitch and axle mounts. Tires should be checked for age via the DOT date code — not just tread depth — because trailer tires over 6 years old are a replacement cost to factor into your offer regardless of how they look. Everything else is negotiable; these three are not.

Is it worth getting a professional RV inspection before buying?

Yes, almost always. A certified RV inspector charges $200–$400 and can find issues that aren't visible without removing panels, using moisture meters, or testing systems under load. For a $15,000–$50,000 purchase, that cost is trivial. Even if you run this checklist yourself and feel confident, a professional inspection before a private-party purchase is still worth the expense. Where it matters less: dealers offering certified pre-owned programs with documented inspection history, and very low-priced trailers where the cost of inspection approaches the cost of the rig.

How do I check for water damage in a used RV?

The three-part water damage check: (1) look up at the ceiling for any yellowing, staining, or soft spots — these trace directly back to a roof leak above; (2) press the screwdriver handle (not the point) into the floor near doors, windows, and the bathroom where water most often pools and soaks in; (3) check sidewalls by pressing gently — solid fiberglass doesn't flex or feel spongy. Also use your nose: mustiness in a closed trailer almost always means moisture that hasn't fully dried.

How old is too old for trailer tires?

The general guideline is 5–6 years from the manufacture date, regardless of tread depth or visual condition. Trailer tires degrade from UV exposure and ozone even when not in use. Find the DOT code on the tire sidewall — the last four digits are the week and year of manufacture (e.g., 2319 = 23rd week of 2019). Tires approaching or past that threshold should be priced and factored into your purchase offer.

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