Toilet Troubles: Why Water Sprays from the Back

One of the least pleasant surprises a homeowner can experience is discovering their toilet spraying water from the back.

While it’s not a common occurrence, it can be both alarming and messy when it happens. Several factors could lead to this undesirable situation, and understanding the potential causes is crucial to finding the right solution.

This identical problem has arisen on hundreds of occasions over the course of the last 10 years during my employment as a maintenance worker at a property with over 250 toilets.

This article will delve into the various reasons that may cause a toilet to spray water from the back, including loose connections, cracked components, and faulty mechanisms. By addressing these issues, you can prevent water damage, maintain the efficient operation of your toilet, and ultimately avoid the inconvenience of an unexpected watery mess.

Image showing the water supply line to the toilet which could be one of the reasons there's water spraying behind a toilet. — Water supply line to the toilet.

Loose Water Supply Line Connection

Cause: One of the most common reasons for a toilet spraying water from the back is a loose water supply line connection. The water supply line connects the toilet tank to the main water supply. Over time, the connection may loosen or the seal may become compromised, allowing water to spray out when the toilet is flushed.

How to fix: To fix a loose water supply line connection, follow these steps:

Turn off the water supply to the toilet by turning the shut-off valve clockwise.
Use an adjustable wrench to tighten the connection between the water supply line and the toilet tank. Be careful not to overtighten, as this may damage the connection.
Turn the water supply back on and flush the toilet to check for any remaining leaks. If the issue persists, consider replacing the water supply line or consulting a professional plumber.

image showing a cracked toilet that could lead to water spraying from the back.

Cracked Toilet Tank

Cause: A cracked toilet tank can also cause water to spray from the back of the toilet. Cracks can develop due to age, manufacturing defects, or sudden impacts, such as dropping a heavy object on the tank.

How to fix: If the toilet tank is cracked, the best course of action is to replace the entire tank. Attempting to repair a cracked tank with sealants or adhesives is generally not recommended, as the repair may not hold up under the pressure of the water. Consult a professional plumber or trusted handyman for assistance with replacing a cracked toilet tank.

image showing where to locate the fill valve in a toilet that might be causing water to spray from the back.

Faulty Fill Valve

Cause: A faulty fill valve can cause water to spray from the back of the toilet. The fill valve controls the flow of water into the toilet tank and should shut off when the tank is full. If the fill valve is damaged or malfunctioning, it may not close properly, causing water to spray out from the top of the valve.

How to fix: To fix a faulty fill valve, follow these steps:

Turn off the water supply to the toilet.
Flush the toilet to empty the tank.
Disconnect the water supply line from the fill valve.
Unscrew and remove the old fill valve.
Install the new fill valve according to the manufacturer’s instructions.
Reconnect the water supply line.
Turn on the water supply and adjust the fill valve as needed.

image showing the fill valve hose that could become disconnected and spray out the back of the toilet.

Disconnected Fill Valve Hose to Overflow Tube

Cause: On many toilets there is a tube that carries water from the fill valve and attaches with clip to the overflow tube, or it will directly connect to a fitting on the overflow tube. If the hose becomes detached in any way, then it will spray wildly like a firehose unattended every time you flush and the toilet tries to refill. The water can easily spray up and run out the lid of your toilet in the back (or any direction).

How to fix: Reattach the clip to the overflow valve that holds the hose, or reconnect the hose to the fitting. If the connection is loose because the hose end has stretched out, cut off 1/4″ of the hose end so that it will create a tighter fit.

image showing how a toilet tank-to-bowl gasket could get damaged and cause the toilet to spray water from the back. — The red gasket in the middle could become damaged or compromised and cause water to spray from the back of the toilet.

Damaged Tank-to-Bowl Gasket

Cause: A damaged tank-to-bowl gasket can cause water to spray from the back of the toilet. The gasket sits between the toilet tank and bowl, forming a watertight seal. If the gasket is worn or damaged, water can leak out and spray from the back of the toilet when the tank is refilling.

How to fix: To replace a damaged tank-to-bowl gasket, follow these steps:

Turn off the water supply to the toilet.
Flush the toilet to empty the tank.
Remove the nuts and bolts holding the tank to the bowl.
Carefully lift the tank off the bowl and remove the old gasket.
Clean the surfaces where the gasket sits on both the tank and bowl.
Install the new gasket according to the manufacturer’s instructions.
Reassemble the tank and bowl, tightening the nuts and bolts evenly.
Turn on the water supply and check for any remaining leaks.

image of the flush valve assembly — The flush valve assembly is everything from the flapper to the top of the overflow tube that sticks out of the water.

Malfunctioning Flush Valve

Cause: A malfunctioning flush valve can cause water to spray from the back of the toilet. The flush valve is responsible for releasing water from the tank into the bowl when the toilet is flushed. If the flush valve is damaged or not sealing correctly, it can cause water to spray out from the back of the toilet.

How to fix: To fix a malfunctioning flush valve, follow these steps:

Turn off the water supply to the toilet.
Flush the toilet to empty the tank.
Remove the toilet tank lid and disconnect the flapper chain from the flush handle.
Unscrew and remove the flush valve assembly.
Inspect the flush valve for damage or wear. If necessary, replace the flush valve with a new one.
Reinstall the flush valve assembly according to the manufacturer’s instructions.
Reconnect the flapper chain to the flush handle.
Turn on the water supply and test the toilet for proper function and any remaining leaks.

Important Takeaways

So, a toilet spraying water from the back can be caused by various issues, such as a loose water supply line connection, a cracked toilet tank, a faulty fill valve, a disconnected hose from the fill valve to the overflow tube, a damaged tank-to-bowl gasket, or a malfunctioning flush valve.

Another thing to check with your toilet is to make sure the toilet base is properly sealed so that water cannot run underneath the toilet itself. Here’s a step by step article on caulking a toilet base if it’s something that you need to take care of.

By identifying the cause and following the appropriate steps to fix the problem, you can prevent water damage and maintain the efficient operation of your toilet. Remember to consult a professional plumber or trusted handyman if you are unsure how to address any of these issues or if the problem persists.