There is nothing worse than a stinky RV, and there is no worse stink than the aroma of urine. So where is it coming from, and what can we do about it? Not only does a bad smell become an annoyance, but long-term exposure to a urine smell can also leave a lasting effect on bedding and furniture materials. There can be a variety of reasons for this stinky situation. 

Why does my RV smell like urine?

Reasons your RV may smell like urine:

• Blocked black tank vent
• Broken black tank
• Clogged black tank
• Toilet flange seal is compromised
• Bowl seal compromised
• The roof vent fan is running while flushing
• Hot weather

Ultimately to cure the foul-smelling problem, you need to find its origin. We’ll tell you where to look, how to fix it, and how to prevent future urine smells. 

We’ve consulted the RV community to get to the bottom of this unpleasant problem. The good news is there are ways to repair and prevent the problem.

Why Does My RV Stink Like Urine

Whether your RV is giving off an unattractive smell because the bathroom needs maintenance or it’s just plain hot out, it needs to be remedied before your next adventure, stat!

RVs Are Built To Contain Bathroom Smells

Generally, RVs are designed to create a barrier between black water tanks and the main unit blocking any unseemly smells. Therefore, the RV tank is usually positioned on the underside of the RV and as close in proximity to the toilet as possible. 

In addition, when you flush, there should only be a small amount of water remaining in the bowl, preventing the smell from penetrating the interior of the RV. In theory, the black water tank underneath should have a pipe from the tank’s top to the RV’s roof. 

This aids the sewage in draining down the sewer line and further on to a dump station. This closed loop system should prevent any methane gasses or ammonia smells from escaping. 

Why Does My RV Bathroom Smell Like Ammonia or Urine

That less than desirable urine aroma can be from a number of sources. Let’s troubleshoot some of the origins of a urine smell in your RV. 

Broken Black Tank and/or Sewage Pipe Leak

A broken black tank or compromised sewage pipe could be a pain point for unsavory aromas. Unfortunately, this problem can be difficult to assess unless you can visibly see the drip and trace it back to its source. 

The Fix: You’ll be a special two part epoxy suited for ABS plastic or a product like Plasti-Mend which contains a special mix of plastic resins and solvents designed to bond to the surface of the black tank. 

If you cannot reach the leak yourself it is best to consult a professional repair service. 

Clogged Black Tank

A clogged black tank is a classic problem in all RVs that is usually the result of not using enough water to flush or an excess of toilet paper. In addition, this can happen if you do not leave the black tank valve shut when parked. You want to keep liquid in the tank to help break down the solid waste which creates an odor barrier from sewer gasses. 

If you don’t, this could result in the ominous “pyramid plug” or waste build up on the tank floor due to ineffective waste breakdown. 

The Fix: Unfortunately, this problem requires the clog to be “punctured” so that water can get through. Once unblocked, you can fill the bowl with water. Driving around will help agitate the remaining clog and then you can dump to clear the rest. Additionally, tank treatments might or might not resolve the problem. 

If all else fails, you can attempt to use the RV black tank flush system to remove the offending clog which is an apparatus that enters through the bowl into the tank. 

Toilet Flange Seal Is Compromised

The toilet flange seal is in charge of creating a barrier between the bowl and pipe between uses. It holds water in the bowl and flips open like a door upon flushing. If the flange is not sealing properly, the odor barrier is broken, which can create a urine smell.

The Fix: Remove the seal and clean it thoroughly. It might also require you to moisturize the gasket. If this does not alleviate the problem, try replacing the gasket, which is a cheap and easy fix. 

Bowl Seal Compromised

A seal at the base of the bowl should create a barrier between the toilet and the black tank, preventing leakage onto the floor. Examine the seal for any breaks. If you discover an improper seal, this is likely the cause of the smell. 

The Fix: Replace the wax ring seal around the base of the toilet by turning off the water to the toilet first. Unbolt the unit from the floor. Scrape the wax seal off the base of the toilet using a putty knife. Replace with a new wax seal and reinstall your toilet. 

The Roof Vent Fan Is Running While Flushing

Most RVs will have a ceiling fan in the bathroom. This needs to be turned off before flushing. Failing to do so will result in a terrible stench. This is because once you flush, this opens the entry into the black tank, and the smell will consequently blow into the entire RV. 

The Fix: This is the easiest of all urine smell fixes! Put up a sign reminding bathroom goers to turn off the fam before flushing. 

Hot Weather

Hot weather is a normal culprit to causing off smells in your RV. This results from the reproduction of excess bacteria in your bathroom, toilet, pipes, and black tank. Lack of water in your black tank can exacerbate this problem because heat has caused excess evaporation. Higher temperatures also make it difficult for aerobic bacteria to break down the waste. 

The Fix: Use plenty of water in your RV holding tank, enough to cover the waste. Treat your black tank with a high quality holding tank treatment and avoid high tank temperatures if possible. 

Mouse Urine

Nothing worse to break the mood of vacation and adventure than the sighting of mice droppings or nests. Mice urine is one of the most strong and persistent scents to remove from your RV interior. If you’ve seen the signs of mice activity, the smell that follows is undoubtedly due to their lack of bathroom manners. 

The Fix: First, open all doors and windows for good air. 

Valves Left Open

Left open valves can cause water to evaporate and waste to dry out. It’s always a good idea to also check sink drains and sewer vent pipes to release odors into the interior of your RV.

The Fix: See Below

How Do You Get Mouse Urine Smell Out Of An RV

Mouse urine is one of the most difficult smells to remove from your RV. But, with a little bit of elbow grease, it can be done. 

1. Open doors and windows for a solid air-out period. Set up a fan to help circulation while you clean. 
2. Put on rubber gloves and a mask.
3. Try to identify the origin of the smell. This is likely near other evidence of activity, especially around any area where you see a “nest.” Look in areas that contain food or nooks and crannies where they might have been holding up. 
4. Use a blacklight if you have one to identify urine areas. 
5. Use enzyme cleaner to spray down upholstery, carpets and other affected surfaces thoroughly. This is often sold as a pet cleaner. 
6. Pull up carpets if you can and clean underneath. 
7. Once the enzyme cleaner is wiped up you can move on to the second solution. Use a 1:1 water and white vinegar mixture in a spray bottle to go over the affected areas again. This is both a powerful neutralizer of smells and a disinfectant. Peppermint oil can also help to cut the smell. 
8. Let all surfaces dry well, and install some slow-release air fresheners or an air purifier to finish.