Usually, if you find that suddenly your entire home doesn’t have hot water, it’s probably because something’s gone wrong with the water heater.
However, in certain circumstances, you may be faced with the perplexing situation where only your bathtub is not receiving hot water, but your bathroom and kitchen sinks seem to be working just fine.
While this problem can initially seem pretty confusing, don’t worry!
It’s usually a relatively easy issue to solve.
So in this article, we’ll walk you through all the possible causes of this issue and how to fix it so you can get your hot water back in no time.
Why is my bathtub not getting hot water?
Your bathtub faucet supplies the hot water to your shower, meaning if it’s not working, you and your family will have no choice but to take cold showers until it’s fixed.
This is sure to draw some ire from your family, so you should correct this problem immediately.
The challenge comes from the fact there are quite a lot of potential causes of this issue.
While it may be tempting immediately to rush out and call a plumber, many common causes of this problem are relatively simple and can be fixed at home.
1: Your ‘anti-scald’ setting is set incorrectly.
You may not even realize that your bathtub has this setting.
Still, many modern bathrooms have a device designed to limit the amount of hot water that can make it through the shower/bath faucet to prevent yourself from getting burned by excessively hot water.
So if for some reason, the settings of this device get changed, it may physically prevent hot water from making its way out of the bathtub faucet
2: The shower’s mixing valve may be faulty
The shower mixing valve, also called the ‘manual valve,’ is a component that’s often found on older showers, so if your home is a little bit older, there is a high likelihood this is causing the problem.
The mixing valve is responsible for mixing the cold and hot water so it can be sent to the main showerhead.
When this component goes bad and becomes faulty, it may not be able to mix the two temperatures correctly and will require either fixing or replacing.
3: Hard water deposit has built up
If this issue developed slowly over a prolonged period, it might have been caused by hard water buildup.
Hard water is a term we use for water with high mineral content.
You may notice white calcium deposits build up around the edge of the faucet, which is a good indicator you have ‘hard water’.
These mineral deposits can also build up within the internals of the shower system, particularly on the inside of faucet valves.
Over an extended period, these buildups can become so substantial that they will heavily reduce or even completely block water flow through the pipe.
So why would this mineral deposit blockage only occur on the hot side?
This problem tends to occur more commonly on the hot side because hot water promotes specific reactions which increase the rate at which these mineral deposits accumulate.
Meaning the hot side usually becomes blocked faster than the cold side.
4: The faucet is defective
Sometimes it might seem strange that a solid hot water supply is being provided to the rest of the home, yet it’s only the bathtub that is running cold.
When this happens, it usually means that the overall hot water supply to the home is working just fine, but something specifically prevents it from reaching the bathtub.
A common culprit of this is a defective faucet.
If you have individual hot/cold faucets you can easily test this by checking if only the cold water faucet is working.
5: A hot water pipe leak
A leak can occur at almost any point in your water system.
But if this happens as hot water is making its way to the faucet, it may either lower the hot water in the bathtub or if the leak is particularly bad, may stop it completely.
You should inspect your home for signs of water damage.
Check for ceiling or wall bulges or mold, which may indicate what has pooled somewhere.
6: A plumbing crossover problem
While technically related to the mixing valve, this is a different issue in which instead of the valve being broken in some way and physically preventing the hot water from making it through.
What can commonly happen is that the valve allows too much cold water to combine with the hot.
Technically hot water is still making it to the bathtub.
It’s being mixed in with so much cold water that it gives the perception of no hot water.
7: The water heater isn’t getting hot enough
The water heater is responsible for taking already cold water, heating it and distributing it around the house.
You may notice that during those extra-cold winter months, the amount of time given to the hot water heater to get the incoming water to the right temperature isn’t enough.
So much so that it might still be cold by the time it reaches the bathtub.
The water heater is relatively easy to adjust, assuming there are no technical issues, so you might have to tweak its setting slightly to better support the current weather.
8: The water demand is too high
Water heaters are designed to hold enough hot water for general use, including washing the dishes, showering, etc.
However, it is possible that if your household uses a lot of hot water, it might not be able to keep up with the demand and you will need to take steps to ‘free up’ more water in your household.
9: Usage is off-sync with a heater’s on-off cycle
Water heaters are not always switched on.
They work more like a kettle where a switch is flipped intermittently.
It will heat the water up and then turn it off.
This helps to lower energy consumption and save money.
If you are trying to shower right at the end of your heaters off cycle when the water is at its coolest, you may find a lack of hot water that can be supplied around your home.
How to fix a bathtub not getting hot water
Out of all the water fixtures in the house, the bathtub is probably the only one that needs a solid and consistent water supply.
If it was your bathroom sink, sure you could get away with washing your hands in cold water without much issue.
Let’s walk through what these problems are and how to fix them.
1: Set up your anti-scald device properly
The first thing to do is ascertain whether you have an anti-scald device installed.
Remove the head of the faucet and you should see a rotating plastic stopper sitting directly underneath it.
You might not even see anything there, so you don’t have an anti-scald device installed and should move on to the next point.
But if you have one installed, we need to change its setting to allow more hot water through the faucet.
Pull the anti-scald device out and then turn it clockwise slightly to increase the amount of hot water it will let through.
Then push the device back down to lock in this setting.
Test the water out by running the faucet for 25-30 seconds and you should notice it is not running hotter.
If the water temperature is too hot or cold, you can further adjust this until it sits exactly where you’d like it to be.
Once you’re happy with the water temperature, you can re-install the faucet head.
2: Fix or replace the faulty mixing valve
As these are usually older components, it’s common to see them go bad due to wear or sudden break.
Unfortunately, this is quite a challenging thing to replace by yourself.
So if you suspect this is the problem, then you should call a professional plumbing service to replace it.
3: Clean out mineral deposit buildups
If you suspect deposit from hard water may have built up and is causing a blockage problem, here’s how to clean the mineral deposits out of the faucet system:
- Start by removing the handle and, depending on which faucet type you have, either unscrew the retaining nut or pull the pin to release the valve.
- Now you can slide the valve housing away using a pair of pliers. If you can’t remove the valve housing, it’s a good indication that an excessive amount of mineral deposit is present.
- Now we need to clean the valve cartridge out by submerging it in vinegar overnight, which will help to break down these tough deposits.
- You should also clean the valve seat by scraping most of the deposit off with a screwdriver and then soak it in vinegar, just like the cartridge.
Once the components are clean, re-install them into the faucet and let the water run for 5 minutes to clear any residue.
It should now be ready to use as normal!
4: Fix or replace the defective faucet
Many elements within a faucet can break, making diagnosing and replacing individual parts quite challenging.
It will often require assistance from a trained plumber and it’s often easier to replace the entire faucet.
The good news is that you can easily replace the broken tub faucet.
Just be sure to purchase a new one that matches in size and diameter.
5: Fix or plug up the hot water pipe leak
Honing in on the exact source of the leak can also be challenging unless you have a good knowledge of your home’s water system.
So unless you are already very comfortable with this process, we recommend contacting a professional plumbing service to ensure the job is done correctly and safely.
6: Correct the plumbing crossover
A temporary solution is to reduce the amount of cold water sent to the shower to make the water hotter.
However, this may result in low pressure as the hot water is already restricted.
If you need a more permanent solution, a professional who will replace the mixing valve completely will need to be called.
7: Increase the water heater temperature
You can easily fix this by increasing the temperature on your water heater’s thermostat and leaving it there for the cold months.
Remember to set it back down once spring arrives or you’ll run an unnecessarily high bill.
8: Free up water pressure
An easy short-term solution to this is to communicate within your household, arrange shower times better and spread activities that require hot water out so the water heater can deal with it.
A more permanent solution is to purchase a water heater with a larger storage capacity or use a tankless model that will be more than adequate to supply enough hot water around your home.
9: Sync up with your heater’s on-off cycle
By being mindful of when your water heater switches on and off, you can time your showers when the water is at its peak level of hotness.
This helps you get more ‘value’ from your heater’s on-off cycle.