Water in the Shower/Bathtub Not Getting Hot? Here’s How to Fix It

Why is the water in my shower not getting hot?

Hot water in your shower is no longer a luxury. It is a necessity; especially on a chilly morning. But why would the water in shower not heat up yet all the other fixtures have hot water?

Showers are designed to mix hot and cold water (for those of us who can’t take cold showers) so that you receive just the right water temperature by turning the faucet handle either right or left. So, why is the water coming out of your showerhead cold only?

If the water in your shower/bathtub is not getting hot, your shower’s anti-scald device has been set too high, or you are dealing with a defective shower mixing valve. In older houses, cross-connected pipes could be the cause due to hot water backflow.

Unless you are dealing with cross-connected pipes, lack of hot water in the shower is something you can easily fix on your own. You only need a few tools and perhaps a new mixing valve.

No Hot Water in the Shower/Bathtub Only

Before you gather your tools and start working on restoring hot water to your shower, you should first determine if the problem is only affecting the shower or all appliances in the house.

Turn on your kitchen or bathroom hot water faucets and let it run for a few seconds. If the water is heating up just fine then the problem is restricted to the shower. On the other hand if you notice that the water from the other faucets is not heating up as well, you have a problem with your water heater.

Dash to the basement or wherever your water heater is located and make sure the valve is fully open. A fully open water heater valve is usually aligned with the pipe carrying the hot water.

If the heater valve is opened and still the water from the faucets and/shower remains cold, the problem is with the heater itself. Some of the reasons for a water heating not heating are:

  • Broken heating element
  • Cracked dip tube
  • Sediment build-up in the tank

A malfunctioning heater is something that I highly recommend that you call in a professional plumber to help you to fix. If the water heater is older than 10 years you should consider replacing it.

If after investing you have confirmed that it is only the shower that is not having hot water, fixing it is easier and cheaper. Here is how to proceed.

1. Adjust the Anti-Scald Device

An anti-scald device, also known as a hot limit stop is a safety device installed in your shower faucet. It limits how far you can turn on the faucet handle in the hot water direction. This controls the hot water flowing from shower head to prevent excessively hot water which can end up scalding your body.

Ant-scald devices are especially helpful if you have little children who may not know how to adjust the correct shower water temperature. It however becomes a nuisance if it is set too high such that you cannot receive any hot water at all.

So, how do you know if your shower faucet’s anti-scald device is the reason your shower water is not getting hot? The only way to do so is by is by adjusting it and checking if the water temperature has improved.

Here us how to adjust a shower faucet’s anti-scald device:

  • Locate a screw on the underside of the shower faucet handle.
  • Use an Allen wrench to remove the screw. Note that you don’t need to remove the screw all the way. You just need to detach it from the stem.
  • Once the screw is loose slide out the handle.
  • Locate the anti-scald device. You will see a plastic piece at the tip of the faucet cartridge. That is the anti-scald device.
  • Adjust it to receive more hot water. You will see 2 arrows on the faucet plate, each showing you which way to turn the device for more hot water or which way for cold water. Usually, to set it to receive more water you turn it counterclockwise. To do this pull it out slightly and turn it in the indicated direction then push it back in. Attach the faucet handle without the screw and turn on the hot water water. Feel if the temperature is as you would want. Adjust the device until you get your desires water temperature.
  • Screw the handle screw back in position.

2. Fix/Replace the Shower Mixing Valve

A shower mixing valve is a device installed at the junction where the shower’s hot water and cold water lines meet. The cold water and hot water mix and flow to your shower head or bathtub spout according to the set water temperature.

Why do showers need a mixing valve? The simple answer is to avoid a cross-connection. As you know, when water is heated it expands. Without the pressure mixing valve, hot water would push into the cold water lines and end up being cooled.

Mixing valves are designed in such a way that hot water cannot flow back to the cold water lines and vice versa. When these valves are defective, that is exactly what happens and hence the reason your shower water is not getting hot water.

Shower mixing valves come with a diaphragm in the middle that prevents hot water from entering the cold water line and vice versa. After years of use, the diaphragm gets worn out, allowing hot water to cross over to the cold water pipe.

If this happens, sometimes you can even get hot water in your kitchen faucet even though you have opened the cold water faucet. Hot water expands and pushed the cold water back.

Most of the time when you cannot get hot water in your shower head or bathtub spout, a defective mixing valve is usually the culprit. It is not very likely that your anti-scald valve will be set too high.

A defective mixing valve will need to be replaced. Here is how to replace a shower mixing valve:

  • Remove your faucet handle. Faucet handles usually come in many different styles. Either way, your shower faucet handle will have a screw at the middle or on its underside.
  • Next remove the cover plate. If you are unlucky, you will have the plate caulked to the wall. If that is the case, cut the caulk out with a knife. The cover plate will also be attached using 2 or 3 screws. Remove them with a screwdriver.
  • The piece you are seeing now is the mixing valve.
  • You can also see the 2 pipes (hot and cold water pipes) which connect at the mixing valve. Depending on the type of plumbing you have in your house, you can see a screw on each of the 2 pipes. Those are “shut off valves”. Use a screwdriver to shut off water to the valve by turning them clockwise. If your pipes do not have these valves you will need to turn off water from your main shut off valve.
  • The shower mixing valve is also attached used a couple of screws. Remove them as well.
  • Once the screws are out, get a good hold of the valve, rock it about and pull it straight out. If it is not coming out easily, grab it with a pair of pliers and pull it out. As you are pulling the valve out, have someone hold a paper plate under it to prevent water already in the lines from dripping inside the wall.
  • Clean the place to remove all debris. You can even turn on the water for a few seconds to flush the lines.
  • Position the new mixing valve and secure it in position using the provided screws. While repairing a mixing valve is possible, installing a new one is the best and long term solution. Do not forget to lubricate the O-ring using plumber’s grease.
  • Using your screwdriver, turn on the water to the mixing valve by turning the 2 screws all the way counterclockwise. If one screw is left partially open you will have low water pressure in your shower head.
  • Put back the shower faucet cover plate and handle. Screw them back in place.
  • Check the new temperature of water in your shower.

If you your shower had all of a sudden stopped getting cold water, this repair will most likely fix it.

3. Fix Cross-Connected Shower Pipes

In plumbing, cross-connection happens when cold water is allowed to flow into the hot water system to balance it out. This system was used in old houses but modern or remodeled houses have pressure-balancing valves instead.

A shower not getting hot water due to cross-connected pipes is not something you can easily fix on your own. You will need to call in a professional plumber to fix it for.

So how do you test for cross-connection in your house? Here is how to proceed:

  • Turn off the water heater’s cold water supply.
  • Look for a faucet in the house with a hot water and cold water lines, open the hot water faucet only.

In this result, you will expect the hot water to run and after sometime, the heater will become empty hence no water will flow out of the faucet. If instead you notice that after the hot water has been depleted cold water starts flowing out of the faucet, you have a cross-connection in your pipes.

In Conclusion, if all the other fixtures in your house have both cold and hot water but your shower/bathtub water is not getting hot, one of these three things is to blame:

  • Anti-scald device has been set too high.
  • The shower mixer valve is defective.
  • There is cross-connection in the pipes.

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