How to adjust an anti scald valve?

How to adjust an anti scald valve - Adjusting anti scald valves correctly can avoid temperature fluctuationsHave 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? If you have ever been in this uncomfortable situation, an anti scald 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. An anti scald valve stops water temperature fluctuations.

Below we discuss what are anti scald valves, in what cases are they useful and how to adjust an anti scald valve.

Why are anti scald valves necessary?

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 shower heads installed.

This kind of inadvertent temperature increase can lead to scalding. Even worse it might cause the person having a bath to jump and fall, leading to other injuries. This puts people like the elderly people and children at high risk since they are more susceptible to shock.

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

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

Most home heaters default to 140°F when shipped from the manufacturer. At this temperature, it takes about 5 seconds for a severe burn to happen.

However, if we instead start using water at the standard recommended temperature (120°F), we are encouraging bacterial growth. Bacteria can thrive at temperatures below 140º F, especially in moist places such as water heaters. 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 Legionnaires 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 danger by maintaining water temperature at a safe level, despite fluctuations in the supply line. They are equipped with mechanism that balances the hot and cold water inputs, keeping the temperature within a safe range.

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

Another major advantage to anti-scald valves is that these valves ensure automatic water supply 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.

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.

SaleBestseller No. 1
Moen 2510 Brass Posi-Temp...
  • TEMPERATURE CONTROL: Posi-Temp valve helps maintain water temperature
  • LONGSTANDING FLEXIBILITY: Built on the Moen M-PACT common valve system, allowing you to update the faucet style in the future without replacing any plumbing
  • CONNECTION SIZE: 1/2-inch IPS connections
  • ORIGINAL EQUIPMENT MANUFACTURER: Authentic Moen replacement part
Bestseller No. 2
Atmama Three-way Thermostatic...
  • US STANDARD FITTINGS -Coming with 3 PCS G1/2 British straight thread to 1/2NPT adapters
  • MARKINGS in FAHRENHEIT-different from others , Temp settings on this water mixer are in Fahrenheit
  • CONSTANT WATER TEMPERATURE - These Thermostatic Mixing valves are the safety feature preventing scalding water
  • LEAK-FREE CONSTRUCITON-one-piece STURDY BRASS body ensures no leaking
  • TIPS: the temperature markings have very little bearing on reality. So this must be calibrated if you're looking for an accurate temperature
Bestseller No. 3
Watts USG-B-M2 3/8" Under Sink...
  • Watts
  • USG-B-M2 3/8"
  • Thermostatic Mixing Valve

Last update 2020-09-26 / Affiliate links / Images from Amazon Product Advertising API

How do anti scald valves work?

Pressure Balanced Valves

A pressure balanced valve is an inexpensive, simple design for and 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.

Thermostatic Mixing Valves

Thermostatic mixing valves have the distinct advantage of not having to be calibrated after being installed once. Thermostatic mixing valves achieve this is by mixing the hot and cold water in a small chamber before letting it pass through the faucet. The chamber contains a thermostatic element which 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 easy to install on a DIY basis.
  • Valves that adjust the water temperature in the pipe itself. These need a bit more work but you can install them yourself if you are handy. Or you can look at the option of spending some money and get a plumber to install it.

How to install your anti-scald valve?

Installing an anti-scald valve is 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 a fair bit of money for yourself.

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 shower head. 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 escutcheon plate and the shower handle. Tighten the screws. This completes the installation.

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 the keep 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. Never ever jump directly under the water to prevent accidental scalding.
  • Adjust your heater thermostat to between 120- and 140-degrees Fahrenheit.
  • Supervise children and 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 useful. If you are looking for adaptive bathing equipment for the elderly, you can read our other article on best shower chairs for seniors.

Gaurav Dhir, B. Tech, is an engineer by training. He also holds the degree of PGDCM from the prestigious IIM Calcutta. Gaurav is responsible for the health and wellness of 4 generations including his son, elderly parents and very elderly grandparents. He is a wellness aficionado and loves keeping and staying healthy.

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