A toilet catching fire sounds like a joke, but it’s a real danger in The Sims 4. If it happens while a Sim is sitting on it, they can get engulfed in flames, and if the fire isn’t put out fast, it can be fatal.
The most common cause is the compost toilet upgrade from the Eco Lifestyle pack. This upgrade occasionally sets the toilet on fire on purpose, as part of burning off compost. Normally the fire is brief and clears before your Sim even notices.
The real problem shows up when there’s nothing to break down the compost. Without insects feeding on it, compost builds up and produces methane.
Since compost is organic and combustible, that buildup eventually causes the toilet to burst into flames, and it’ll keep happening repeatedly.
Build a bug farm. Insects break down compost and stop it from building up, which cuts down on fires significantly.
Empty the toilet regularly if you don’t have a bug farm set up yet.
Skip the Instant Upgrade option when upgrading toilets.
Avoid the compost upgrade entirely if you’re not planning to maintain a bug farm.
One toilet model in particular, the Old Time Antique Toilet, seems to catch fire more often than others, so keep a closer eye on it if you’re using one.
If your toilet is catching fire and you haven’t installed the compost upgrade, check these instead:
Gremlins lot trait. Lots with this trait cause appliances and plumbing, including toilets, to break or malfunction overnight.
Childish trait or Mischief aspiration. Sims with these can autonomously prank the toilet, even while using it themselves. This usually shows up as purple smoke rather than an actual fire, but it’s worth ruling out.
If a Sim is on the toilet when it ignites, act fast:
Have them jump into a shower immediately. Water puts out the fire.
Keep showers placed near toilets in your builds so a Sim can reach one quickly.
If the fire isn’t put out in time, the Sim can die, so don’t wait.
Consider replacing the toilet with a different model to see if the fires stop.