Why do hot water tanks have such a bad rep?

Alex Klohe wrote:We’ve been off grid since 2014, family of 4. Our best water heating has proven to be a 50 gallon electric hot water heater plumbed to our old kitchen queen cook stove heater coil, then a mixing valve, then to a propane fired on demand hot water heater.

In the deep winter the propane never kicked on because the incoming water was already hot. Shoulder seasons it would heat minimally until the summer when it did all the work.

We have since built a walker continental rocket stove and LOVE IT. The only setback is no water coil. Since we only run it a couple hours a day on average it doesn’t pay to put one in. OUR PROPANE USAGE IS CRAZY.

Next step is to hook up the panels we just got directly to the water heater coils in the tank (which have never been used) and crank up the temperature. Hopefully that will help with the propane usage.


Our two cents.

Mine too! Even without using a gas fired on demand water heater, boiling the kettle for dishes and showers is a lot in the summer and the shoulder periods. In the winter, the Walker is great. We use it maybe 6 hours aday in the winter but I have run the exhaust pipe above our bed so it heats the kitchen/dining area and our bedroom. As the stove backs onto our bedroom wall we also get lovely heat stored in the wall.  I have a reservoir next to the stove top which provides enough hot water in the morning to do dishes, etc. And we shower early evening to benefit from the masses of boiling water we generate at that time. Our water tank sits in the side chamber that moves the hot air from the plate to the oven before exiting the chimey. It's uncompressed -we lift the lid off the top and scoop water out. I wish I had a bigger receptical to hold more water as it's such a treat having access to instant hot water-instead of boiling the kettle! I will be experimenting with thermosyphoning by attaching copper pipes wrapped around the base of my exhaust pipe to an old electric water boiler, without an element, filled via cold water supply. To have water on tap in the winter would be absolute luxury.

Nancy Reading wrote:This was an interesting topic for me since I have only ever had hot water tanks in my houses, albeit not large super insulated ones as Matt suggests. I suspect that this is something that people who take showers rather than baths need to be a bit more aware of, since it is inhaling the infected water seems to be the greatest risk.

Judith Browning wrote:One of the downsides, that I hear, to a tank water heater is the energy used to hold it at a temperature that does not grow bacteria.

There are ways around that apparently. If you want a read, see how the UK gets around this: HSE technical guidance on hot water systems. It depends a lot of how the system is plumbed, and I don't know what is normal in the US. The temperature of incoming mains water is a factor, as well as whether the water is recirculated.
Legionella isn't a big issue in the UK in domestic settings, usually only in more complicated municipal buildings I believe.

Legionella was unheard of in the United States until PVC piping became the dominant material for plumbing use.  The reason for this is that Legionella defends itself from the heat by forming a "mother" on the inside of a pipe, but copper is a toxic surface to almost every form of single celled life.  I'm pretty sure that just about every tank heater sold in the United States today has a copper lined tank, for this exact reason; so the threat of getting Legionella spores in your lungs from a tank heater is probably an over-blown concern today, no matter what the thermostat is set to.  That said, they are designed to heat to 135 F, in order to be able to provide at least 110 for an extended period of demand; and that is hot enough to slow cook to destruction just about any form of human pathogen known.