Toilet, Sink and Shower Pan Repair on RVs and Fifth Wheels
Written by RV Systems Lead, RV Systems and Electrical Lead, OCRV Center. Reviewed by Claims Coordinator
In shortA bowl that will not hold water is a seal. A toilet that rocks is a cracked closet flange and a wet subfloor. Fixture work runs $200 to $5,500.
What does RV toilet, sink and shower repair involve?
Fixture repair covers toilet ball seals and closet flanges, sink drains and traps, shower pans, surrounds and valves. Owners from Rancho Santa Margarita bring the unit to Yorba Linda, where the toilet is lifted, the flange is inspected and the decking underneath is metered before anything is refitted.
- Water in the bowl at night and gone by morning is a bottom seal
- A toilet that shifts when you sit on it has broken its flange
- Shower pans crack where nothing supports them under the foot area
- Sink slip joints soak a cabinet base for months without a puddle
- Price range
- $200 to $5,5001 to 25 labor hours at $260 per hour
- Labor rate
- $260 per hourMechanical and electrical department
- Typical turnaround
- 1 to 6 shop daysLonger where decking under a flange has to be renewed
- Written estimate
- $150Credited in full against an authorized repair
- Fixtures serviced
- Dometic 310 and 320, Thetford Aqua Magic V, Sealand VacuFlush, Tecma macerating
Last verified
Three fixtures in an RV share one drain system, and from the bathroom doorway their failures look the same. What separates a part and an hour from a floor rebuild is where the water goes. Into the tank is a nuisance. Into the decking is a building repair with a plumbing part at the top of it.
So this page is organised around that question rather than around the fixtures: bowl seals, the closet flange, shower pans and the voids builders leave under them, and sink drains, which carry no pressure at all and still destroy more cabinetry than anything else on the list.
Where the water ends up decides the size of the job
Start by asking where the water is when you find it, not which fixture you suspect. Water in the bowl that has gone by morning is going into the black tank, and nothing is reaching the floor. Water standing on the flooring at the base of the toilet is a seal or a flange at the floor, and that water has been going somewhere for a while. A damp cabinet base under the galley with a dry bathroom is a drain joint that carries no pressure behind it at all.
That single distinction sets the estimate. A bowl seal is a part and an hour of labor. A cracked closet flange has been feeding decking for however long the toilet has been able to move, and the plumbing portion of that repair ends up being the smallest line on the sheet. It is why the toilet comes off before anything is quoted rather than after something has been tried.
- Bowl empties overnight, floor dry: a bottom seal, going to the tank
- Wet flooring at the toilet base: the flange or the seal above it
- Toilet shifts under load: cracked flange, soft decking, or both
- Damp cabinet floor under a sink: a slip joint or a basket strainer
- Pan creaks and drops underfoot: no support beneath the fibreglass
Bowl seals, flush balls and the breaker at the top of the feed
A gravity flush RV toilet holds water in the bowl on a rubber ball or blade seal pressed against a machined seat by the flush linkage. It dries out, takes a set, and collects scratches from grit and from whatever the owner has been cleaning it with. Once it stops sealing, the bowl empties down into the tank overnight. That is a nuisance rather than a hazard, and the odour that follows it back up is the tank rather than a leak in the room.
Dometic 310 and 320 units use a ball with a pedal or hand linkage. Thetford Aqua Magic V and Style II use a flush ball with a separate water module and a sprung pedal. Both carry a vacuum breaker in the feed at the top of the bowl, and a failed breaker is what makes water run continuously down the porcelain or the plastic instead of arriving through the flush ring. Replacing a seal is quick. Replacing a seal onto a seat that has been running dry and is now pitted is not, so we look at the seat before quoting the cheap part.
Before you proceed
Household bowl cleaners and anything chlorinated will harden an RV toilet seal inside a season. Water and a soft brush is the entire maintenance regime, and it explains why two identical toilets can be five years apart on seal life.
The flange under the toilet and the deck under the flange
The flange is a plastic ring bonded or clamped to the top of the drop tube, and the toilet bolts down through two open slots in it. It is the most consequential single part in an RV bathroom, because it is the only thing keeping tank side waste out of the decking. It cracks at those slots, almost always because somebody met a rocking toilet with a longer wrench, and once cracked the toilet can move. Every movement works the seal, and the seal is the last line between a dry floor and a wet one.
By the time an owner notices the movement, the lauan under the flange has usually been damp long enough to lose its glue line, so there is nothing solid left to bolt a replacement flange to. We cut back to sound material, rebuild the deck around the drop tube, then bed a new flange and set stainless closet bolts to a torque figure rather than to feel.
- Lift the toilet and photograph the flange and seal exactly as found
- Meter the decking outward from the drop tube in four directions
- Cut back the compromised material and rebuild the deck
- Bed a new flange with an RV seal and stainless bolts set to torque
- Refit, flush twenty times with weight on the seat, and recheck the base
Vacuum and macerating toilets fail on entirely different parts
Plenty of higher end coaches and van builds carry no gravity toilet at all. Dometic Sealand VacuFlush systems hold vacuum in a line between the toilet and a bellows pump, so a bowl that will not hold its seal is a bellows, a duckbill valve or a leaking joint along that line rather than a fault in the toilet itself. Owners report it as the pump running on long after the flush, which is the vacuum switch never seeing the level it wants.
Tecma and similar macerating toilets grind and pump instead, which lets a builder site a toilet a long way from its tank. Their failures are mechanical: an impeller stopped by a wipe, worn brushes, or a control board that has taken water. We test those with a clamp meter on the supply, because a macerator drawing high current and turning slowly has already told us what is inside it.
Why a shower pan cracks in the same place on every unit
A one piece RV shower pan is thin fibreglass or ABS sitting on whatever the builder put under it, which on a great many units is a partial frame and a gap. Stand over the gap for a few hundred showers and the pan deflects at the same point every time until a star crack opens, typically just forward of the drain where a foot lands. Water then travels under the pan and along the decking, which is why a shower leak so often gets reported as wet flooring beside the entry step instead.
Repairing the crack without correcting the void beneath it wastes the owner's money. The pan gets supported first, with bonded rigid foam and timber packed to give continuous bearing, and then the laminate is repaired or a replacement pan is fitted. The drain penetration gets its own look while everything is open, since the shower drain flange and its gasket are a separate common leak point and they are only reachable with the pan out or from below.
Sink drains carry no pressure and still ruin cabinets
Because a drain is not pressurized, it leaks slowly and it leaks straight into cabinetry. The usual suspects are a slip joint nut hand tight at build and never touched again, a brittle ABS trap, a basket strainer whose putty has dried and shrunk away from the sink rim, and a flexible tailpiece somebody stretched to reach a drain that had shifted. None of them make a puddle. They make a swollen cabinet floor and a smell nobody can source.
Galley sinks matter more here than bathroom sinks, because that cabinet usually contains the drain, often a run of supply tubing and sometimes the pump as well, so one damp corner has three candidate sources. We separate them the same way every time: dry the cabinet, run the sink with the supply shut off, then pressurize the supply with the drain untouched.
What fixture work costs, and why the unit comes here
Fixture work bills at $260 per hour from the mechanical and electrical department across a band of $200 to $5,500. A ball seal and a vacuum breaker on a reachable toilet sit at the bottom. A flange replacement with decking renewal under a bathroom, or a pan replaced and correctly supported, sits at the top. Parts carry standard markup, sales tax applies to parts and materials, labor is not taxed, and a written estimate is $150 credited in full against an authorized repair.
We do not offer a mobile service for this work, and there is no roadside version of it. Lifting a toilet needs somewhere to drain it and somewhere to set it down. Cutting back wet decking produces debris that belongs in a bay with extraction. The load test at the end needs a supply and a dump connection. Owners from Rancho Santa Margarita take the 241 to the 91.
On cost
Where decking under a flange reads wet, the plumbing repair and the floor repair are quoted as separate lines. You are entitled to see which part of the number is the toilet and which part is the building.
Which vehicles we do this on
Diesel pushers and luxury fifth wheels bring vacuum and macerating systems, plus residential style pans with long unsupported spans. Class C units put a wet bath in the smallest space in the coach, where a flange sits directly over a wheel well. Destination trailers sit in one spot for years, which is the condition under which a slow flange leak becomes structural. Class B vans carry cassette and macerating arrangements, and mobile salons run shampoo bowls plumbed on the same principle as a galley sink.
What is included
- The toilet comes off, every time
- Nothing useful about a bathroom floor can be established with the toilet bolted down. It is lifted, the flange and seal are photographed, and the drop tube joint is inspected.
- Metered readings around the drop tube
- Pin meter readings taken outward in four directions from the flange, recorded with distances, so the extent of wet decking is a number rather than an opinion.
- Pan deflection checked loaded and unloaded
- A shower pan is measured with somebody standing in it, because an unloaded pan sitting on a void looks perfectly sound from above.
- Drain side isolation on a damp cabinet
- The sink is run with the supply shut, then the supply is run with the drain dry, which separates a slip joint weep from a pressurized leak in two short tests.
- Correct seal hardware rather than household parts
- RV specific flange seals, stainless closet bolts set to torque, and new putty or gasket under a basket strainer instead of whatever was there.
- Fill, flush and load test before releasewhere applicable
- The toilet is flushed repeatedly with weight on it, the shower is run with somebody standing in the pan, and the sink is filled and drained fast.
How the work runs
Establish where the water ends up
30 minutes
Bowl level marked and timed, floor around the base checked by hand, cabinet bases opened and felt at the back corners. This first pass sorts the nuisance faults from the ones that have been feeding a subfloor, and it takes very little time.
Lift the toilet and read the deck
1 hour
The toilet comes off onto plastic, the flange and seal are photographed as found, and the decking is metered outward from the drop tube. Owners see those readings before any scope is written, because they set the size of the whole job.
Load the shower pan and look underneath
45 minutes
The pan is checked with weight in it and, where a bay or a basement allows, from below. What we are looking for is the void, not the crack, because the void is what caused it and it is the only part of this that has to be corrected.
Separate drain leaks from supply leaks at the sinks
30 minutes
A damp galley cabinet has three candidate sources: the sink drain, the supply tubing, and the pump on units that put it there. Running them one at a time with the others isolated resolves which one in about five minutes.
Rebuild in the right order
3 to 20 hours
Structure first, then plumbing, then finish. Deck repaired around the drop tube, flange bedded and bolted, pan supported and sealed, traps and tailpieces renewed rather than retightened. Sequence matters here because a flange bolted to soft decking will simply loosen again.
Test with weight on everything
1 hour
Twenty flushes with a person seated, the shower run at temperature with somebody standing in the pan, both sinks filled and dumped at full flow. A fixture that passes unloaded and fails loaded is the whole reason this step exists.
What this costs
$200 to $5,500
1 to 25 labor hours at $260 per hour, mechanical and electrical.
- Parts at $100 or less carry 100 percent markup. Parts over $100 carry 35 percent. Special order parts require a full non refundable deposit at order.
- Sales tax of 7.75 percent applies to parts and materials. Labor is not taxed.
- A 50 percent deposit is taken at authorization on any job over $2,000, with an additional 25 percent when parts arrive on any job over $10,000. Final balance is due at pickup.
- A ball seal and a vacuum breaker on an accessible toilet sits at the bottom of this range.
- A flange replacement with decking renewal under a bathroom sits at the top.
- Shower pan replacement is priced with the support correction included, because a pan refitted over the same void cracks again.
How estimating is billed
- Written repair estimate: $150, credited in full against an authorized repair.
- In depth diagnostic, scan and programming: $285 per hour, one hour minimum, credited in full against an authorized repair.
- In shop pre purchase inspection: $400 to $1,200 depending on unit size and systems count.
- Insurance walk ins are accepted during posted hours. All inspection and estimating work is performed in shop at the Yorba Linda facility.
What you will notice first
- The toilet bowl is dry every morning and holds water fine during the day
- The toilet moves slightly when you sit down or when you rock it by hand
- A dark ring or a soft edge in the flooring immediately around the toilet base
- Water trickling continuously down the inside of the bowl after a flush
- The shower pan creaks and drops underfoot in one spot near the drain
- A star shaped hairline crack in the pan just forward of the drain
- The cabinet floor under the galley sink is swollen at the back corner
- A sour smell in the bathroom that does not change after the tank is dumped
How this fails, and what we do about it
| Failure mode | How we diagnose it | The fix |
|---|---|---|
| Bowl seal no longer holding water | Fill the bowl, mark the level and leave it two hours. A seal fault drops the level with no water anywhere outside the toilet. Lift the seal and look for scoring on both the rubber and the seat it presses against. | Replace the seal, and inspect the seat before quoting. A pitted seat that has been running dry will chew a new seal inside a season, and in that case the whole flush assembly is the honest repair. |
| Cracked closet flange with wet decking | Rock the toilet by hand with the closet bolts loose and then tight. Movement either way means the flange or the deck under it has failed. The toilet comes off and the decking is metered outward from the drop tube in four directions. | Cut back the compromised decking to sound material, rebuild the deck around the drop tube, then fit a new flange with an RV specific seal. A household wax ring cannot tolerate the flex a trailer floor sees at freeway speed. |
| Shower pan cracked at an unsupported span | Stand in the pan and feel for movement, then check the same spot from below where access allows. Cracks radiate from the point of maximum deflection, which is nearly always just forward of the drain rather than at the drain itself. | Support the pan first with bonded rigid foam and timber packed to continuous bearing, then repair the laminate or fit a replacement pan. Filling a crack over a void reopens it, usually within a few dozen showers. |
| VacuFlush that will not hold vacuum | The bellows pump runs on long after the flush completes. A gauge on the vacuum line shows it never reaching the switch setting, which places the fault anywhere along the line rather than in the toilet. | Replace the bellows and both duckbill valves as a set, then leak test the vacuum line and every joint in it. Chasing one component at a time on a vacuum system is how these turn into three visits. |
Why it happened
- A ball or blade seal that has dried, taken a set and picked up scratches from cleaning products never intended for a rubber sealing face
- Closet bolts overtightened at some point in the unit's life, cracking the plastic flange through its bolt slots so the toilet can rock
- A shower pan installed over a partial frame, leaving an unsupported span that flexes at the same point every time somebody stands on it
- Slip joint nuts on a sink tailpiece that were hand tight from the factory and have vibrated loose over thousands of towing miles
- A failed vacuum breaker at the top of the toilet water feed, which lets supply water run down the bowl instead of into the flush ring
- Dried and shrunken plumber's putty under a sink basket strainer, so waste water passes the rim of the sink rather than the drain
Parts and brands we work with
- Dometic 310 and 320 pedal flush toilets with ball seals, blades and floor flange kits
- Thetford Aqua Magic V and Style II toilets with flush balls, water modules and pedal springs
- Dometic Sealand VacuFlush systems with bellows pumps, duckbill valves and vacuum switches
- Tecma macerating toilets with impellers, shaft seals and control boards
- Lippert Better Bath one piece shower pans, surrounds, drain flanges and gaskets
- Dura Faucet and Phoenix Faucets shower valves, diverters and cartridges plus ABS traps and tailpieces
What not to try yourself
- Tightening the closet bolts harder because the toilet rocks. The flange is plastic with open slots and that is precisely how it cracks in the first place.
- Fitting a household wax ring under an RV toilet. Wax is designed for a house floor that never moves, and an RV floor moves every mile.
- Cleaning a toilet seal with anything chlorinated or abrasive. The seal is a rubber sealing face and household bowl products harden it within a season.
- Standing in a pan that already flexes to see how bad it is. Each flex extends the crack, and a crack that reaches the drain boss turns a repair into a replacement.
Which vehicles we do this on
Vehicles we perform Fixtures and Pans on
Diesel PusherDiesel pusher repair means working on a rear engine coach built on a welded Freightliner XC or Spartan rail, with a full body painted fiberglass shell and large basement baysLuxury DestinationLuxury fifth wheel repair covers frame flex at the axle hangers under residential weight, independent suspension components, six point auto level hydraulics and hard flooring at slide thresholdsClass CClass C motorhome repair centers on the cabover bunk, the joint where the coach body meets the factory van cab, and the stick built or laminated house behind itDestinationDestination trailer repair addresses frame flex at the axle hangers on a long light rail, roof ponding because the unit sits level for months, and sidewall bow from slides left extended all seasonClass BClass B camper van repair covers the van unibody, the bonded fiberglass high top or pop top, and the RV systems the coach builder installedSalon and SpaMobile hair salon repair covers styling chair base mounts, the backwash bowl drain penetration, chemical attack on the floor, mirrors bonded to a flexing wall panel and rear overhang loads under a spa chairI lift the toilet on every single one of these, including the ones the owner is certain is just a seal, and I get pushback about it maybe once a month. The reason is that a rocking toilet has been leaking at the flange for as long as it has been rocking, and lauan decking does not recover. I would rather spend an hour showing somebody a meter reading of thirty percent moisture six inches from the drop tube than hand them a new ball seal and see the same unit back next spring with a soft floor and a much bigger number on the estimate.
Appendix: questions and answers
- Why does the water disappear from my RV toilet bowl overnight?
- The ball or blade seal at the bottom of the bowl has dried out or been scratched, so bowl water slowly passes into the black tank. Nothing reaches the floor. Fill the bowl, mark the level and wait two hours to confirm. Check the sealing seat too, because a pitted seat destroys a new seal quickly.
- Does a toilet that rocks always mean the floor beneath it is wet?
- Nearly always, yes. Movement means the flange has cracked at its bolt slots, and every movement works the seal that keeps waste out of the decking. We lift the toilet and meter outward from the drop tube in four directions before quoting, because that reading decides whether this is a part or a floor rebuild.
- Can a cracked shower pan be repaired, or does the whole pan come out?
- Either can be right, and the deciding factor is the void underneath rather than the crack. A pan supported to continuous bearing and then laminated repairs well. A crack that has reached the drain boss, or a pan sitting over a large unframed gap, is replaced. Filling a crack over a void reopens it in weeks.
- Is a household wax ring acceptable under an RV toilet?
- No. Wax is designed for a house floor that never moves, and an RV floor flexes constantly at freeway speed. The wax deforms, loses contact and stops sealing. RV specific flange seals are made to tolerate that movement, and they cost very little compared with the decking a failed seal destroys.
- What makes a VacuFlush pump keep running after the flush finishes?
- The system is not reaching its vacuum setting, so the switch never satisfies. Suspect the bellows, both duckbill valves, or a leaking joint anywhere in the vacuum line rather than the toilet. We gauge the line and replace bellows and duckbills as a set, because chasing one part at a time turns this into three visits.
- Why is the cabinet under my galley sink damp when the sink looks fine?
- That cabinet usually holds three candidates: the sink drain with its slip joints, a run of supply tubing, and on some units the pump. Drains leak slowly because they carry no pressure. We dry it, run the sink with the supply shut, then pressurize the supply with the drain dry, which identifies the source in minutes.
Open a file on this repair
Tell us the vehicle, what happened and whether a claim is open. We will tell you what the scope looks like and what it takes to get you back on the road.
Or call (949) 799-3387