Hot Water Runs Out Before Bath is Full: Causes & Fixes

It’s quite disturbing to climb into a shower one day expecting hot water only to be shocked by freezing water or a temperature so low it can’t warm your body. If you have either a tankless heater or an electric tank, you may fix the issue by making several adjustments to increase or decrease the water pressure. However, keep in mind that you may be constrained by your home’s plumbing limitations.

Hot and Cold Water Knobs in a Bathtub

Hot water will run out before the bath is full due to a water heater & faucet malfunction, clogged pipe, leak, rusty galvanized pipes, low water pressure, & a broken dip tube. Fix it with pipe insulation, high water flow rate, a hot water recirculation pump, tankless water heater, & a new dip tube.

Where do bathrooms get hot water from?

Water coming to your bathrooms makes its way through several system pipes and is usually cool or cold, depending on the year or season. Getting the water warm enough to either take a shower or bath is fine with a water heater. Its primary function is heating water to have access to hot water whenever you need it.

There are two types of water heaters: 

  1. The tankless water heater is slowly gaining popularity, and the system heats water on demand. 
  2. The second one is the water heater with a tank, found in most households. This kind of heater heats water in bulk and stores it making it readily available for when you might need it.

Hot water runs out before the bath is full

Below are the reasons why you might not be getting enough hot water:

1. Water Heater Malfunction

Bathtubs, in general, require a lot of water, and if you are getting enough water but not hot enough, you may have a malfunctioning water heater. 

If your water heater is electric, one or more of the heating elements might not work, causing the water to flow cold or lukewarm. The thermostat may need replacing or only need to make a few tweaks like lighting the pilot light in a gas heater again or restarting the water heater. 

2. A Clogged Pipe

A clogged water pipe might be why your tub is not getting enough hot water, especially if your house is old with pipes that have served you for decades. 

Old pipes tend to get clogged with deposits of minerals due to chemical imbalances in the water. These deposits can cause water blockages hindering hot water from reaching your tub. When installing or reinstalling a shower, always ensure you budget for new pipes.

3. A Defective Faucet

Your problem may also be a defective faucet, especially if you turn the handle to open the faucet and no water comes out. When this happens, it probably means something is broken between the stem and seat of the valve that controls the water flow. 

While this may be a pain, it does not necessarily mean it’s bad news, but it is a cheaper fix compared to the alternative fixes. 

4. A Hidden Leak

Having a leak within your hot water pipe may cause the hot water to flow poorly or not flow at all. If you start noticing any water damage stains on the ceilings or crawl space, you most certainly have a leak. 

While leaks are harder to identify when the tub is on the first flow of an apartment or slab foundation, a plumber may have an easier time finding them.

5. Galvanized Pipes

In case you have an electric tank-style water heater, then the water coming out should be the same pressure as the cold water entering. If the water leaving the heater has more pressure than the water entering, it will not have enough time to heat, reducing the temperatures of the water you are receiving. This can be done by regulating the water pressures to match.

Galvanized pipes can affect the amount of water pressure coming to the shower since they’re prone to rusting and thus reduction in the water passages in the pipes. The result is that less water reaches the water heaters. 

6. Insufficient Water Pressure

Usually, valves are installed in water lines that lead to bathrooms to shut the water off in case of repairs. Having these valves partially closed might be why you do not have hot water, as it reduces the water pressure in your house. The result is that the water won’t have enough time to heat up in the shower. 

You can find the pressure regulator from the incoming line and increase the pressure by loosening the locknut.

Generally, if you are working with a tank water heater, ensure the water’s distance and pressure are suitable for the temperature you want. If the solutions below do not work, you probably have a small tank compared to the water consumed. 

Also, if your water pressure issue is in line with sharing water with other people, then your only solution is retrofitting your plumbing.

7. Broken Dip Tube

The dip tube has the role of pushing cold water to the bottom of the tank or heating. If it isn’t in good working condition, it’ll not move the cold water sufficiently leading to poor heating. The result is lukewarm (rather than hot) water coming out of the faucets.

Fixes to hot water running out before bath is full

Below are several hacks and quick fixes for your bath:

Causes Fixes 
Water heater malfunction
Clogged pipes
Defective faucet
Rusty galvanized pipes
Insufficient water pressure
Broken dip tube
Routine maintenance
Insulate pipes
Replace with higher flow rate fixtures
Install hot water recirculation pump
Use a tankless water heater
Replace or fix the dip tub
Call for an expert

1. Routine Maintenance

The best way to ensure you always have hot water running through your pipes is by doing routine checks and maintenance. This helps you identify any issues early on before it becomes a nuisance. 

Remove shower heads by hand or with a wrench to check for sediments and mineral deposits which may lead to low water pressure.

In addition to that, having a professional periodically have a look can help you catch on minor issues and save you a lot of costs.

2. Insulate Pipes

If your water pipes are to blame for your troubles, adding insulation may help improve your situation. Insulating pipes helps keep water warm by maintaining the heat, ensuring effective hot water delivery. 

Generally, insulating pipes has more than one advantage as it also reduces the mold growth rate and makes your plumbing quieter. 

It is important to note that insulating is ideal for pipes in exterior walls and long stretch piping. Also, each type of insulation is different, and you should research widely before selecting the most suitable option for you.

3. Replace Fixtures with a Higher Flow Rate

If your problem is caused by either a showerhead or sink faucet with a low-pressure rate, the most probable and straightforward solution is to replace it. Get a fixture whose limit is higher and preferable to you while still keeping in mind the work of a faucet is to reduce your water consumption. The higher the pressure, the higher the water consumption rate, which will increase your water bill.

Low water pressure in the shower can also be due to flushing the toilet. You can prevent this by simply avoiding toilet flushing when taking a shower.

4. Install a Hot Water Recirculation Pump 

The most ideal solution for most people when it comes to cold-water issues is installing a hot water recirculating system. The pumps circulate back your unused water to the heater storing hot water in specific places, ensuring less time is spent heating water while saving on energy costs at the same time.

A great alternative is installing a pipe that circulates water in a loop from your home’s furthest fixture thus removing water traveling to and from the heater. This doesn’t work for older homes and, instead, you can have a pump installed in the water heater and have the sink-like device at the furthest fixture. This creates a different water circulation system using your home’s pipes.

5. Upgrade to a Tankless Hot Water Heater

A significant transition you can make to increase the pressure and keep your water delivery hot is replacing your water heater. Instead of installing a newer tank model, consider upgrading to a tankless water heater as it heats water instantly, allowing you to have a constant flow of hot water. 

Besides that, a tankless water heater can take up to 5 gallons per minute, ensuring water won’t run cold on you.

6. Replace the dip tube

Replacing the dip tube will allow the tank to properly circulate hot water to the top and cold water to the bottom for heating. The result is uniformly-heated water coming out of the faucets for your bath.

Final Thoughts

If none of these methods above have worked for you, the best option is to seek a professional and have an accredited plumber look at your pipes. Avoid trying to fix issues that are beyond your knowledge since you can cause more harm than good to your plumbing system.

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