Is your water heater large enough for your bathtub?

You’re all set to try out your new whirlpool.  You’ve lit your candles, you’re turned on some Enya, you’ve poured yourself a glass of wine, youcleaned the gunk out of the jets last week, and you’ve filled your tub with hot water… oh wait.  Your tub is only halfway full, and you’re out of hot water.  Bad times.  This will happen if the water heater isn’t large enough for the bathtub.

Determining if a water heater is large enough for a bathtub is actually pretty simple; the water heater tank should be about 2/3 the size of the bathtub.  For example, if you have a 40 gallon water heater, it would be just large enough for a 60 gallon bathtub.   A very small bathtub might hold 40 gallons, while a larger single person bathtub could easily hold 100 gallons or more.

My bath tub holds 110 gallons (pictured above), and my 50 gallon water heater couldn’t even fill it with enough hot water to use the whirlpool jets.  That’s how my house was built, back in 1998.  Can you believe it?  For a bathtub this size, a 75 gallon water heater would have been about right.

In order to use the whirlpool at my bathtub, I cranked up the temperature on my water heater from a safe 120 degrees to a dangerous 140 degrees (or so).  With 140 degree water coming out of the hot water spout at my bathtub, I could mix in a lot of cold water to get the water to a comfortable temperature, and I was able to fill up my bathtub.

That’s nice for me, but what about my three-year-old son?  This wasn’t safe at all – at 140 degrees, it only takes a few seconds to get 2nd or 3rd degree burns.

To make up for this, I installed a tempering valve at the hot and cold water pipes right above my water heater.  Now, cold water gets mixed in with all of the hot water coming out of the water heater, making it seem as though my water heater is much larger than it is.  The water that comes out of the faucets can be adjusted at the tempering valve, and I have it set at 120 degrees.  This was a much cheaper alternative to replacing my water heater or buying a second water heater, and it was fairly easy to install.

Done and done.

Reuben Saltzman, Structure Tech Home Inspections - Email - Home Inspector Minneapolis

    

Water Heater Replacement Options

When I replaced my first water heater, I was excited to get something larger, more efficient, and maybe even a little sexier.  As it turned out, getting a different type of water heater wasn’t my best option, and now I end up telling my customers the same thing.  If you’re in need of a new water heater, chances are pretty good that you have a 40 – 50 gallon gas water heater, and your best option for replacement will be with the exact same type.

A standard gas water heater is a pretty simple device – there’s a tank that holds water, a burner at the bottom of the tank, and a vent that takes the exhaust gas out of the house through gravity (the warm air rises).  There are several other types of water heaters, and I’m going to list some pros and cons of each type.

Standard Gas - This is what makes up the bulk of water heaters in Minneapolis and Saint Paul – I would estimate 95%.  They have a low cost, they're easy to replace, and they recover hot water relatively quickly.  On the downside, energy is lost by keeping water heated all day.  If you're replacing a standard water heater and there is a problem with the chimney or flue (which usually means it’s not up to code), it can be very expensive to repair the chimney or bring it up to code.

Powervent - These are similar to standard gas water heaters, but instead of the exhaust gases rising up and out of the house, a fan forces the exhaust gases through a plastic pipe out the side of the house.   The biggest advantage is that the exhaust gases don't need to rise up the house through the roof - these water heaters can be vented right through the side of the house.  These are a great option if there are problems with an existing standard water heater flue.  Unfortunately, they cost about twice as much as a standard water heater.  I’ve also noticed that they are frequently installed wrong; I would guess that about 50 – 75 percent of the powervent water heaters that I inspect are incorrectly installed.

Tankless – This type of water heater definitely generates the most interest.  These water heaters only heat the water that you use, so you’re not wasting money by keeping 40 gallons of water hot all day.  They use less energy, take up less space, and provide an endless supply of hot water.  Unfortunately, they cost about three times as much as a standard water heater, and it's very expensive to convert from a standard water heater to a tankless - so much so that getting a payback in energy savings is out of the question.  They also provide a limited volume of hot water; a standard tank will give you all the hot water you want until it's gone, but a tankless water heater produces a limited amount at once.  Click the following link for an in-depth research paper on tankless water heaters.

Electric – Electric water heaters are probably the easiest to install and easiest to replace.  There is no venting required, so they can be installed in small places or in places where it would be difficult or impossible to run a vent.  The biggest downside to electric water heaters is that they take a long time to recover hot water.  Once you’re out of hot water, you’re out for a long time.  I don’t recommend electric water heaters if you have the choice of using gas instead.

Reuben Saltzman, Structure Tech Home Inspections - Email - Minneapolis Home Inspections