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

How complicated can it be to take a temperature reading?

In the State of Washington, when a Licensed Home Inspector tests the temperature of the water, they 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.

hot water

Water temperature way too hot!

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 lead me 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 highest to lowest 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.  Not really–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.  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 temperature at this bathroom and usually it agrees with the reading (or very close to it) that I got at the kitchen.  In Washington State, limiting water temperature to less than 120 degrees F has been required at tubs/showers since 2003, so it is a good idea to check the tub and shower hot water temperatures of these newer homes.

By the time I have gone all through the other levels of the home and finally get to the basement, 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.

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 you get to the inspection, the water heater has been sitting idle and cooling off.  Because there has been no demand for hot water it has 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 need 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 every day 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.

And it is not just a concern for babies.  As our population is aging, the elderly and infirm are also vulnerable to scalding.

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.

While taking an accurate temperature reading in the context of a home inspection, proper adjustment of the temperature can be even more difficult–but that may be the topic of another post.



Charles Buell, Real Estate Inspections in Seattle


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Deadband—what is water heater “deadband?”

If you are thinking that this post is about the Grateful Dead Band, I am sorry to disappoint.  It is  “loosely” about Jack & Jill in the shower—-but not about them being in the shower together—if they showered together this would not happen.

I have done many posts about conditions related to water heaters—this is but another.

This one may be a bit “technical” but it will hopefully help explain a condition that occurs all too often in homes.

Water Heater “DEADBAND”

The question varies, but it usually goes something like this.  Jill asks, “How come some times there seems to be plenty of hot water for both me and Jack to take showers—-and other times there is not?”

Well Jill, it is probably due to “deadband.”  While deadband can be an issue with gas water heaters it is very common with electric water heaters.  You see, the thermostat on your water heater has a range at which it turns itself off and turns itself on (Jill could not help but think about how this might apply to her and Jack in other more interesting ways).  It is this “range” that causes the problem (how true, how true, thinks Jill).  Some water heaters are worse than others (DEFINITELY true, thinks Jill).

Let’s say that Jill starts out with a fully heated water heater at 120 degrees Fahrenheit.  She takes a nice leisurely, relaxing shower and uses most of the hot water—-but not quite enough to get to the low point of the thermostat to make it kick back on to heat more water.  Now Jack comes along an hour later (after the lazy butt sleeps in)—all set to take a nice long hot shower (Jill is thinking cold shower)—-only to run out of hot water as the thermostat finally kicks in to heat more water.

To simplify things, I have drawn a little graph to help visualize the basic concept.


So what is the solution?  There really isn’t one that doesn’t involve keeping the heater at higher than safe, recommended temperatures (120 degrees Fahrenheit).

Keeping the heater at higher temperatures (so that there is more water to dilute) also means that the thermostat’s low range is always going to be higher than what is a satisfactory temperature for a nice long shower.  Installing tanks with more storage capacity is another solution as well.

Perhaps the best solution would be to install what is called a “tempering valve.”  This is a clever device that allows you to have the water heater set at say 130 degrees Fahrenheit and mixes a little cold water into the stream whenever you use hot water so that you don’t ever get more than 120 degree water out of your faucets.  This also protects the heater from the growth of bacteria in the tank that is encouraged or maintained by 120 degree water.

Sounds like Jack will be in plenty of hot water now—no more cold shower treatment.



Charles Buell, Real Estate Inspections in Seattle


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TPRV’s, PRV’s and your water heater.

Many homes have water heaters in the basement—or some other part of the home.

Sometimes the TPRV (Temperature Pressure Relief Valve) drain on the water heater runs to the exterior—sometimes it merely runs to the floor. As has been discussed before, the drain can not run up hill because water will be trapped against the valve leading to possible failure of the valve.


The TPRV drain must not run up hill

The TPRV drain must not run up hill

TPR Valves that only drain to the floor can cause damage to interior finishes if there is no acceptable place for water from the TPRV to drain to—like a floor drain.  Current regulations require pans with drains under the heater if damage could be caused by leaks from the heater.

In some jurisdictions, when the TPRV drain can not run to the exterior due to the exterior grade being higher than the valve on the tank, the plumber will sometimes install a “PRV” (Pressure Relief Valve) on the plumbing system. This valve is only sensitive to elevated water pressure—-a condition that would relate directly to increased water temperature. The PRV is set at a lower pressure so that in the event that the house water system pressure was to exceed safe levels, the valve would open to lower the pressure. Being set at a lower pressure it will “blow off” before the higher setting of the TPRV, which might damage the finished interior of the home in the event that the TPRV were to open.

This next picture shows a typical installation.


Water heater with a TPRV and a PRV

Water heater with a TPRV and a PRV

Note the normal TPRV on the side of the tank with the drain going down to the floor area. In the picture one can see the top of the foundation and how it would be difficult to run the drain from the TPRV to the exterior without running up hill. Up near the ceiling there is the PRV and its drain to the exterior just above the top of the foundation.


Charles Buell, Seattle Home Inspector

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