What is the “actual” water temperature in my home really?

The post previous to this was about water heater Deadband.  This post is related in that it shows us another way that deadband affects use of hot water and the safety concerns posed by deadband.

How difficult can it be to figure out what the water temperature in a home is?How hot is the water in your home really?

In the State of Washington, Licensed Home Inspectors are required to report when the water temperature is above 120 degrees and then advise the client that the recommended high temperature is 120 degrees Fahrenheit.

What I have found, over and over again, is that if I take the temperature reading at the kitchen—-where I start my inspections—it might read 118 degrees F and falsely be led to think that the temperature is OK.

Because most kitchens have mixing valves, I know that sometimes the temperature might actually be a little higher than that—so I know I am going to check it somewhere else too.

After the kitchen, the next part of the inspection usually moves to the highest level of the home.  The idea is that you want to test all the plumbing from the highest level and then down to the  lowest level so that by the time you get to the crawl space it will be flooded by all the leaking so that you might not even have to do the crawl space.  Of course this is meant tongue-in-cheek—but you get the idea.

Lots of bathrooms—at either the tub or the vanity—may have faucets that are not mixing valves so that it is easier to get an accurate temperature reading at those locations.  That said—lots of newer tub and shower fixtures have mixing valves with anti-scald features which again prevents accurate temperature readings.  Regardless, I usually check the temperatures at this bathroom and the temperatures are usually consistent with the reading (or very close to it) that I got at the kitchen.

By the time I have gone all through the other levels of the home and finally get to the basement (if there is one), I often find the laundry sink which almost always has separate faucets, I know I can get a good temperature reading there.  I take the temperature and all of a sudden it is 130 degrees Fahrenheit.

At first you scratch your head and say, “How can this be?”

The answer is that “time has gone by”—-perhaps an hour or two or three.

When the inspector arrives at the inspection, the water heater has been sitting idle and has been cooling off.  Because there has been no demand for hot water it may have cooled all the way down to its low point—the temperature at which the thermostat would normally kick in and start heating the water.  However, these simple thermostats operate the best with a pronounced change in temperature for them to kick-in.  The temperature of the water might go even below the normal kick-in temperature.  During the normal everyday operation of these thermostats, the temperature differential is likely between 5 and 10 degrees but can vary up to 25 degrees—the difference between whether a baby gets scalded or not.

These swings in temperatures are especially true of vacant homes.

The moral of this story is that it is best protocol to take the water temperature later in the inspection than it is to take it right at the beginning of the inspection—for the most accurate indication of what the temperature actually is.

In the end, it is not difficult to figure out the temperature—but the best protocol must be followed.


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