Tank type electric water heaters—hard to beat.

Super Insulated Water Heater

Me in my water heater

Everyone that knows me, knows I spend a lot of time in my basement playing with my water heater.

I have always been skeptical of the claims made about different types of water heaters and I have never had anything more than anecdote to sort out any truth of these claims.

About 6 months ago I bought an electric meter to install on the water heater so I could keep track of exactly how much electricity it uses.  This takes some of the extrapolation and guessing out of equation.

What I am writing here in no way clarifies everything but it clearly demonstrates the whole topic needs to be revisited by people with more money and testing facilities than I have.

Some of this inquiry is in answer to advertising by on-demand water heater manufacturers that would have us belief tankless-type heaters are god’s gift to water heaters and that tank type heaters are no longer a viable way to heat water. 

There are lots of pros and cons to both types.

It is my premise, if water heaters came with a LOT more insulation than is currently required, they can remain competitive in cost to operate and certainly in cost to install. 

The initial costs and maintenance costs associated with tankless water heaters is still considerably higher than tank type heaters–and lets face it, they are as complicated as under the hood of your car.

An interesting thing happens when you install an electric meter on your water heater.  It becomes very difficult to use hot water “normally.” This is because of the nagging little voice in the back of your head that questions whether you are wasting hot water while you are doing the dishes, doing the laundry, taking a shower or washing the cow.  That said, the ratio should remain similar even if the numbers end up somewhat higher.

Meaningful numbers can still be found when comparing operating costs of an off-the-shelf heater compared to one that is super-insulated.

About two months ago, my heater died.  When I replaced it, I replaced it with another tank type heater that was 15 gallons smaller than the previous heater.  I decided I would monitor costs for a period of time prior to super insulating it.  The tank comes insulated to R-13.  I would ultimately insulate the tank to R-40.

My installation is further complicated by a re-circulation loop.  I also wanted to determine the operating costs of the loop.  Just how much did it add to water heater operating costs?  In addition I wanted to see performance differences of keeping the tank and loop at 135° F and 120° F.  I suspect I could have gotten better numbers if I monitored for a whole year or several years, but I was merely looking for hints of the truth.

Super Insulated Water Heater

Insulated to R-40

At 135° F, the operating costs of the loop resulted in an additional 15 cents per day.  The loop operated for 15 minutes an hour between 6am and 10 pm. 

The loop with super insulated lines and tank also results in having a larger volume of hot water sitting in the tank waiting to be used.  The hot water circulating to the bottom of the tank mixes with the incoming cold water reducing the amount of time it takes to bring all the water up to the set temperature. 

If power is lost, I still have a tank full of hot water for a couple of days.  With the tankless you immediately have nothing.

My loop is a thermosiphon loop (no pump) and has a timer with an electronic valve to control how much it operates.  The loop to the kitchen and back to the water heater is approximately 88 feet and insulated to R-20.  I consider this cost per day to operate the loop as insignificant.  The cost is mostly offset by the savings related to not wasting water.

After insulating the tank to R-40, the per day costs to heat water to 135° F averages 92 cents per day.  Prior to insulating the tank, the average daily cost was about $1.20.  This is approximately a savings of 24%.  This results in a payback on the $152.00 cost to install the R-40 insulation of 1-3/4 years.  Over the 20 year life of the water heater (typical of my area) that could be a savings, at current electrical rates, of $2060.00.  This is the cost of more than 5 water heaters based on the $400.00 cost of my recent water heater purchase. 

I know of no comparable way to get this kind of savings with a tankless water heater and of course initial costs are much higher with the tankless.  Maintenance costs over 20 years is going to be close to the savings of the super-insulated tank type heater.  Keep in mind that estimates of cost to operate tankless water heaters do not include increased costs to maintain re-circulation loops.

I realize no one is likely to do their water heaters what I did to mine to achieve these numbers. 

This exercise is to expose the silliness of what we currently require of manufacturers. 

Manufacturers could certainly add insulation to R-40 (or higher) at the time of construction much cheaper than I can do it in the field.  This seems like a no brainer if we are serious about conserving energy. Of course this only applies to electric water heaters that can be heavily insulated at the sides, top and bottom.

Another factor that comes into play, is that the size of the tank can be much smaller, which even further reduces annual costs to operate the heater. It also deals with possible problems with replacing larger heaters that would be bigger if insulated to R-40.  There is no reason standby-costs on a tank-type water heaters can’t be brought under 50 cents a day–probably under 30 cents a day if the tank is 40 gallons or less.  With a super insulated tank, a 40 gallon tank should be more than adequate for a family of four.

When are we going to start requiring manufacturers to install more insulation on their heaters?

Temperature behind the insulation

The temperature of the tank behind the added insulation is 100° F

Charles Buell, Real Estate Inspections in Seattle

Home Sports—Extreme Back-drafting

back-drafting1Back-drafting of water heaters is when the exhaust gases, instead of going up the vent and outside of the home, draft back into the space around the water heater. 

If the water heater is in the living space, this can mean that combustion by-products are ending up in the home.  This is not just an issue with Carbon Monoxide, which is certainly a consideration, but it also can add large amounts Carbon Dioxide and Moisture to the indoor environment. 

Additional water and carbon dioxide in the indoor environment adds another layer to our never ending battle with maintaining good indoor air quality. 

A properly burning gas water heater will only create carbon dioxide and water, so contrary to what many people believe, Carbon Monoxide is not “necessarily” going to be an issue.  If this was not the case we could never use gas ranges in a home.

There are several causes of back-drafting–some of which will likely lead to Carbon Monoxide production and some less likely.  Insufficient air supply to the heater can result in Carbon Monoxide production and then if we add to that improper installation of the vent (very long horizontal runs in relation to the vertical run of the vent for example), and obstructions in the vent, Carbon Monoxide loaded combustion by-products can enter the home.  Add to this that Carbonic Acid (Carbon Dioxide in H2O) is created with faulty combustion/venting that will result in corrosion of metal components that come in contact with the vent gases.

When the water heater starts up, it is not uncommon for some amount of gases to back-draft out the draft hood as low temperatures in the flue are overcome and venting can happen.  This is especially true of vents that share flues with other gas appliances–such as the furnace.  We use water heaters year round, so a good part of the year the chimney can be considered over-sized for the water heater.  Of course summer time flue temperatures are likely to be warmer than in winter so overcoming temperature differences in the flue/vent will not be quite as important a consideration. 

An argument can be made that all gas appliances should have their own vent or better yet that they should all be direct-vent type appliances.  In direct vent appliances combustion air and exhaust air by-pass each other from a location outside the home and there is no communication with the indoor environment.

Another way to create back-drafting at the water heater is when the improperly installed or blocked vent is shared with another gas appliance (such as a furnace) and the furnace vents back out through the water heater.

As homes become tighter and tighter, back-drafting can be created by any number of exhaust fans operating throughout the home when the water heater needs to operate.  The path of least resistance for replacement of the air being exhausted by the fans might just be the water heater vent.  So in this sense back-drafting can be an indication of insufficient makeup air for the exhaust fans and likely means the water heater does not have adequate combustion air as well. 

Making sure that homes stay “pressure neutral” so that these types of problems don’t occur is essential in modern construction.  Again direct vent appliances eliminate this problem as related to the appliances–but it will not solve the problem of air intake for the exhaust fans.

Atmospheric pressures differences such as during inversions can also contribute to poor venting of the gas appliance.

A proper vent hat is also an important part of the whole venting system in promoting proper venting by keeping vermin out and preventing wind from blowing down the pipe under some condition.  It is not uncommon to find these vents filled with wasp’s nests–especially on systems that are idle for long periods of time.

So what does back-drafting look like?

The following picture is visual evidence of extreme back-drafting.


If you look closely at the picture you can see all the signs.  Notice the yellow tag all melted around the Temperature Pressure Relief Valve (TPRV—and, for all of you that know better, yes it’s drain pipe is missing).  Notice how the galvanization has completely been eaten away on the supply nipple at the center of the picture.  Notice the much melted plastic ring around that same pipe.  Keep in mind that the exhaust gasses are slightly acidic, which accounts for the corrosion visible on the draft hood (the cone shaped device behind the TPRV).  The white powder on the top of the tank is the condensate that develops when the moisture from the vent gases evaporates.

In this next picture we can see some of the corrosion on the vent pipe along the long horizontal run to where it connects to the furnace vent.  In this case the horizontal run is almost as long as the vertical run—not a good arrangement to promote good venting of either appliance.  Also it should be mentioned that the single wall vent pipe does not have adequate clearances to the wood beam it travels under.


It will likely not be possible for your inspector to identify all the possible causes of back-drafting, but its presence gives itself away pretty easily in many cases.  Because of the ease with which conditions for back-drafting can develop, items that can burn or melt should never be left on top of your gas water heater.  I routinely find charred and melted belongings on top of gas water heaters–from soccer shoes to the water heater’s installation manual (very common).

I like to think that in a few years this blog post will be outdated, as we give up on draft hood type water heaters and convert entirely to direct vent type water heaters of one kind or another.  We will be all the safer for it.

By Charles Buell, Real Estate Inspections in Seattle

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When home inspectors need referees

There is an old joke about soccer referees.  “The referee is always right and even when he is wrong he is still right.”As a Seattle Home Inspector I run into this sometimes when I call something out to be repaired by a licensed XYZ, only to be told by the XYZ that the defect “meets code.”This happened after an inspection a while ago regarding the TPRV drain on a water heater.  The code is pretty clear about these drains–even as to the types of pipes that can be used.  One requirement (the one that required a referee) is that there cannot be any “restrictions” in the line.  Restrictions might include, kinks, too many elbows or being reduced in size.  One thing that I frequently find installed on these drains is “flexible” connectors.  It is questionable that over the length of the connector—especially bent into a pigs-tail–that the inside diameter would measure ¾” over its length.  Add to this that at each end of the connector there is a plastic washer that has a 5/8” diameter hole, and it is pretty clear that these flexible connectors do not meet code.

Flexible connectors are not allowed on the TPRV drain

Flexible connectors are not allowed on the TPRV drain

Contacting the head plumbing inspector for the City of Seattle, he concurred with my assessment–and I was able to rest my case.  Good thing the referee has a referee in this case.

Another good reason for not using these connectors is that they can easily be pushed into a position that might result in water being trapped against the valve.  This could lead to failure of the valve due to corrosion.

Who are the buyer and seller to “believe” when a conflict of opinions like this comes up in the inspection report?  Who is the more “credible” authority regarding plumbing issues?  Is it the “generalist” Licensed Home Inspector or the “expert” Licensed Plumber?

I have no clue what the answer is (actually I do), but I do know that if the water heater finds its way through the roof of the house, and someone is seriously injured, all parties E&O will likely be called upon.

Even though, as in this case, the plumber was “wrong”—-I know that next time it might just be me that is wrong.  The willingness to be wrong is important for all of us to embrace—because it will happen.  This is what referees are for.


By Charles Buell, Real Estate Inspections in Seattle


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