How to Adjust an Anti Scald Valve (Thermostatic Mixing Valve)?

Have you ever been in a shower when you were suddenly hit with hot, scalding water just because someone else ran a tap or flushed a toilet in the house? Didn’t you just hate it?

How to adjust an anti scald valve - Adjusting anti scald valves correctly can avoid temperature fluctuations

If you have ever been in this uncomfortable situation, an anti-scald valve (thermostatic mixing valve) can solve this problem for you! Anti-scald valves maintain the temperature of water in a shower, bathtub, or faucet at a set level at all times and stop water temperature fluctuations.

Over the long term, an anti-scald valve will save you money, by reducing the flow of hot water. It will also save you time which you will spend adjusting the valve.

Check out the top-selling anti-scald valves from Amazon below.

Bestseller No. 1
Speakman Cpv-3000-IS Sentinel...
4 Reviews
Speakman Cpv-3000-IS Sentinel...
  • Forged brass valve body & glass filled resin bonnet
  • 1/2 inch female Copper sweat inlets & shower outlet
  • Integral stop allows user to shut water off at valve
  • Adjustable temperature limit Stops with built-in check valves
  • ASME a112.18.1/CSA B125.1 and ASSE 1016 certified
Bestseller No. 2
KES BRASS Anti-Scald Pressure...
2 Reviews
KES BRASS Anti-Scald Pressure...
  • BRASS VALVE: Faucet body is made from high quality brass, ensuring quality and longevity.
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  • Pressure balancing and ceramic temperature regulating cartridge, equipped with adjustable temperature limit stop and integral stops
  • Built-in service stops, check valves
  • Connection Size: 1/2 NPT threads. Package includes valve, faceplate and handle.
Bestseller No. 3
Thermostatic Mixing Valve For...
15 Reviews
Thermostatic Mixing Valve For...
  • DO YOU WANT TO SET YOUR WATER BOILER AT 140° F SO YOU CAN KILL HARMFUL BACTERIA BUT ARE WORRIED ABOUT CHILDREN GETTING SCALDED? TEMLOCK thermostatic mixing valve allows you to set your water heater at 140° F. Then simply set the valve at the safe temperature of around 120° F.
  • DO YOU WANT THE WATER TEMPERATURE OF YOUR SOLAR HOT WATER SYSTEM TO BE MORE CONSTANT? TEMLOCK thermostatic mixing valve will help you maintain hot water temperature to your desired temperature, for example 120° F.
  • ARE YOU ALWAYS RUNNING OUT OF HOT WATER BUT CANNOT INSTALL A LARGER TANK? TEMLOCK thermostatic mixing valve allows you to keep your current boiler. Simply set your water heater at higher temperatures and set the thermostatic mixing valve at the safe temperature of around 120° F. With these settings, the valve will use less hot water from your boiler !
  • DO YOU NEED TO CONTROL THE WATER TEMPERATURE IN YOUR PEX RADIANT FLOOR HEATING OR OTHER HYDRONIC APPLICATIONS? No worries ! Use TEMLOCK thermostatic mixing valve to set water temperature to your desired level.

Last update 2021-01-19 / Affiliate links / Images from Amazon Product Advertising API

Below we discuss what anti-scald valves are, how they are useful, and how to adjust them.

Why are anti-scald valves or thermostatic mixing valves needed?

Temperature fluctuations can be caused due to changes in pressure in either the hot or the cold line. For example, when someone flushes a toilet, cold water flows to the toilet and reduces the pressure in that line. Therefore, less cold water is available in the pipes.

Anyone bathing at that moment may feel a sudden increase in water temperature. This situation can be further worsened if the plumbing is either narrow or clogged, or there are several showerheads installed.

This kind of inadvertent temperature increase can lead to scalding. Even worse it might cause the person who is taking a bath to get startled and lose balance, leading to other injuries. This puts elderly people and children at high risk since they are more susceptible to shock.

An anti-scald valve or a thermostatic mixing valve is the perfect solution for this kind of problem. The video below tells you more about a thermostatic mixing valve and how it works.

All about Thermostatic Mixing Valves

While having the water too hot can cause scalding, it is a lesser-known fact that the water temperature being too low is also a cause for concern.

Also read : Adaptive Bathroom Equipment – How to Make a Bathroom Safe for the Elderly?

Most home water heaters default to 140°F unless any changes have been made to them. At this temperature, it takes about 5 seconds for a severe burn to happen.

Instead, if we start using water at the standard recommended temperature (120°F), we may be encouraging bacterial growth. Bacteria can thrive at temperatures below 140º F, especially in moist places such as water heaters.

How to adjust an anti scald valve - Anti scald valves ensure water temperature will not suddenly change
Anti scald valves ensure water temperature will not suddenly change in faucets or showers

The elderly and children, who have a weaker immune system are susceptible to the bacteria Legionella which thrives at lowered temperatures. These bacteria are the root cause of Legionnaire disease, which is a severe form of Pneumonia. (source)

The Legionnaire disease is known to spread primarily through water droplets. Factors such as water temperature and the mineral content of the water impact its growth.

Therefore, it is important to keep the water in the heater at a higher temperature (140°F+), while using a lower temperature at the point of bathing or washing (110° – 120°). This is where anti-scald valves come into the picture.

Anti-scald valves protect against both these dangers by maintaining water temperature at a safe level, despite fluctuations in the supply line. They are equipped with a mechanism that balances the hot and cold water inputs, keeping the temperature within a safe range.

A woman showering

Anti-scald valves or thermostatic mixing valves also increase the availability of hot water. They draw hot water more slowly from the pipes.

These valves ensure automatic water supply is cut off in case of a failure on either the hot or the cold water supply side. This minimizes the possibility of an accident due to a sudden disruption in the pipeline supply.

How do anti-scald valves work?

Pressure Balanced Valves

A pressure balanced valve is an inexpensive, simple design for an anti-scald valve. Essentially, a piston or a diaphragm is put inside the faucet, and it regulates water flow based on pressure changes.

If the hot water pressure drops, the piston limits the amount of cold-water flow, and vice versa. If the heater temperature is changed, this kind of anti-scald valve must have its heating settings changed along with it.

Also read : Best Transfer Benches for the Elderly

Thermostatic Mixing Valves

Thermostatic mixing valves have the distinct advantage of not having to be calibrated after being installed once. They operate by mixing the hot and cold water in a small chamber before letting it pass through the faucet.

The chamber contains a thermostatic element that expands and contracts basis the temperature change. Increased temperature expands the element, blocking the hot water, and if the temperature reduces, the element contracts, letting in more hot water.

Types of Anti-scald Valves

There are two basic types of anti-scald valves:

  • Screw-on valves that reduce hot water. These are DIY and easy to install.
  • Valves that adjust the water temperature in the pipe itself. You can install them yourself if you are handy, or you can hire a plumber to install it.

How to install your anti-scald valve?

Installing an anti-scald valve can be a fairly lengthy exercise that involves plumbing expertise, special tools and instruments, and a lot of patience. You may be better off paying a plumber to do the job since it can be technically intricate for some.

However, if you do have the skill to do this DIY project, you can save on the plumber expense. The video below shows how to install a Thermostatic Mixing Valve.

How to install a mixing valve

Items you may need:

  • Flat head screwdrivers & pliers
  • Adjustable pipe wrench
  • Safety goggles
  • A reciprocating saw with a metal-cutting blade
  • Tile cutting blade
  • Support blocks, pipe straps
  • Plumbers putty


  1. Turn off the water supply. Remove the handle which controls hot and cold water.
  2. Use the diamond blade to cut the bathroom tiles behind the handle and reach the pipes that would be connected to the existing valve.
  3. Use a reciprocating saw to cut the pipes. Remove the old valve and piping above where you cut, to make way for the new valve to be installed.
  4. Dry fit the new pipes to the hot and cold pipes where the old valve was detached.
  5. Remove the valve spindle of the new valve and disassemble the pipes.
  6. Solder the new valve to the pipes.
  7. Reinstall the spindle which was removed in step 5. Turn on the water and check for leaks (make sure that there is no water flowing out because that can be a costly mistake later on). Adjust the valve if the water is not the right temperature.
  8. Reinstall the old handle.
  9. Turn on your handle and showerhead. Inside the valve is a rotational stop which looks like a gear. This controls how hot the water is allowed to get. Once you adjust this as per your requirement, put the handle back on.
  10. Use plumber’s putty against the rear section of the valve.
  11. Screw the cover plate to the wall.
  12. Slip a rubber gasket behind the escutcheon plate and the shower handle. Tighten the screws. This completes the installation.

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How to Adjust an Anti-scald Valve?

Follow the steps below to adjust an anti-scald valve.

  1. Turn off the water. Before starting anything, make sure to turn off the water to the faucet of the bathtub. Some models will even have a water shut-off provision on the outside of the valve.
  2. Remove the handle. You might need to use a set key or an Allen wrench for this purpose, and it may involve a screw or else a hub.
  3. Remove the valve cover retainer sleeve. The sleeve will usually be protruding out from the center of the valve.
  4. Remove the temperature stop. This would be there on the stem of the valve. Make sure to take note of the side facing out so that you can install it back correctly.
  5. Reinstall the temperature stop. The temperature stop will have multiple settings based on the type and brand of valve used. Adjust the stop according to the setting you need (this might take multiple attempts to understand whether hot is clockwise or anti-clockwise). Once done, place the stop into the correct position.
  6. Put the valve cover back on. You may need to screw it in, depending on the process that you followed earlier.
  7. Replace the valve handle. Take care to fit the cover gently, otherwise, it might break or worse, the handle may get stuck.
  8. Turn the water back on, and enjoy the optimally heated water in the shower!


Anti-scald valves are meant to provide you with safety against scalding on the one hand and bacteria on the other. Homes with vulnerable age groups such as seniors and children should certainly consider installing them, so as to avoid unnecessary accidents and disease. Apart from anti-scald valves, below are some other precautions that should be taken in order to avoid bathroom incidents due to scalding:

  • Test the water temperature before getting into a bath for at least a few seconds. To prevent accidental scalding, never ever jump directly under the water.
  • Adjust your heater thermostat to between 120- and 140-degrees Fahrenheit.
  • Supervise children and the elderly around hot water. Keep them away from hot liquids as well.
  • Get a plumber or contractor to ensure that pipes, valves, or heaters are regularly checked for wear and tear and are replaced well in time before they become faulty.

We hope that you found this article on how to adjust an anti-scald valve is useful for you.

If you are looking for adaptive bathing equipment for the elderly, you can read our other article on best shower chairs for seniors.

About Rachel Ann

Rachel Ann Tee-Melegrito is a licensed Occupational Therapist in the Philippines and in the United States. She has a Masters in Education with a major in Child Development and Education. She currently teaches at one of the top 4 universities in the Philippines. An INFJ-T, Rachel is introverted yet idealistic, a perfectionist yet also a sensitive, empathetic person. She is a creative individual who loves learning, reading, designing, and writing. She lives in the Philippines with Kenn, her husband, Cali, their daughter, and Pepper, their Mini Schnauzer.