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Did you know that you can dramatically increase your water heater’s capacity without installing a new water heater? anti scald valve

Do you regularly run out of water in the mornings when the whole family is trying to get ready for work and/or school? Do you have to stagger showers so that everyone has enough hot water?

It can be frustrating trying to work around the lack of enough hot water for the whole family.

I have a solution for you – and it costs a lot less than buying a new water heater.

It involves installing a small device on your water heater. The device is called a whole-house anti-scald valve or a thermostatic mixing valve.

What is a Thermostatic Mixing Valve?

A thermostatic mixing valve is a device that mixes hot water as it leaves the water heater with some cold water to provide hot but tempered, water to the faucets in the home. 

anti scald valveThese devices, also called whole-house anti-scald valves, ensure that water at a safe temperature is delivered to the faucets in the home. You choose the final temperature of the water by adjusting a dial on the device.

Once the device is installed and the temperature is set, you are done. You basically set it and forget it.

Anti-scald mixing valves will allow you to keep the water in your water heater very hot such as 150 or 160 degrees. As the hot water leaves the water heater headed for a shower or sink, for example, it will be mixed (also called tempered) with just enough cold water to bring the temperature down to the desired temperature.

Benefits of a Whole House Anti-Scald Mixing Valve

These anti-scald or tempering valves have some great benefits.

  1. They can prevent someone from being scalded by water that is too hot. They do this by lowering the temperature of the water that reaches a sink, tub, or shower to a safe level.
  1. They can help prevent the growth of dangerous bacteria in your water heater. They do this by allowing the water in the water heater to be hot enough that any bacteria in the water heater is killed.
  1. They essentially increase the capacity of your water heater.

The next section explains how this is accomplished.

(See my other post that goes into detail about preventing scalds and bacteria growth.)

How Does an Anti-Scald Valve Increase the Capacity of a Water Heater?

Let’s say you have a 50-gallon water heater, and that you have the water temperature set to 110 degrees. With this water heater, you basically have 50-gallons of 110-degree water.

(You will actually have a little more than 50-gallons because more water is being heated as you use hot water. So, the actual amount of hot water that you can get from a 50-gallon water heater is probably closer to 55 or 60 gallons.) For simplification, we will ignore this additional amount in this discussion.

Now, let’s suppose that you have an anti-scald device installed on your water heater. With this device installed, you can safely set your water heater to produce 150-degree water without the risk of someone getting scalded.

Let’s assume that the temperature of the water coming into your home is 60°.  The anti-scald mixing valve can combine one gallon of 150° water from your water heater with just enough cold incoming 60° water, to bring to the final temperature down to 120° (or whatever temperature has been set).

In this example, you would end up with 1 ½ gallons of 120-degree water for every gallon of 150° water taken out of the water heater.

This means that by the time you have run all 50 gallons of water out of your water heater, you will have used a total of 75 gallons of water.

So, you have effectively increased the size of your water heater from 50 gallons to 75 gallons – a 50% increase!! And you did this all for less than about $150, since these devices cost about $125-$150.

If you have some basic plumbing skills, you should be able to install it with just a few additional parts.

If you are not comfortable doing the work yourself, you can hire a plumber to install it for you and I wouldn’t think it should cost more than about an hour’s worth of labor.

Once the anti-scald device is installed, you will have protected your family from scalding water, and from potentially-dangerous bacteria. At the same time, you will also have “increased” the capacity of your water heater.

You get three benefits for the price of one. 

© 2021 Mike Morgan

This article was written by Mike Morgan, the owner of Morgan Inspection Services. Morgan Inspection Services has been providing home, septic and well inspection services throughout the central Texas area since 2002. He can be reached at 325-998-4663 or at No article, or portion thereof, may be reproduced or copied without prior written consent of Mike Morgan.

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