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Thank you, Chas863. This is exactly what I needed to know.
Is this also true in a shower that has a mixing valve with a lever? Is the cold water to the shower drawn from the main inlet? YES
In other words, the cold water line is going INTO the hot water tank and the hot water line is coming out of it? YES
Let me explain it this way. There is only ONE line of water coming into your house. This would be considered the COLD water line. This line serves ALL the cold water faucets in the house plus any external faucets you may use to water the flowers or wash your car.
Once the cold water line gets inside your house, at some point it "splits" and part of water goes to the cold water faucets in the house and part goes to the hot water tank. Water coming OUT of your hot water tank is then run in separate lines to each hot water fixture. Once the water goes to the hot water tank, the only way it would be mixed again with the cold water is at a "mixing" faucet itself such as in your shower and perhaps in your kitchen sink and perhaps your bathroom sink.
If the water in your sink comes out of a single faucet, then it is a "mixing" faucet that mixes the hot and cold water inside the faucet itself. If your sink has a separate faucet (spout) for the hot water and a separate faucet (spout) for the cold water, then the water is NOT mixed inside the faucet.
Let me explain it this way. There is only ONE line of water coming into your house. This would be considered the COLD water line. This line serves ALL the cold water faucets in the house plus any external faucets you may use to water the flowers or wash your car.
Once the cold water line gets inside your house, at some point it "splits" and part of water goes to the cold water faucets in the house and part goes to the hot water tank. Water coming OUT of your hot water tank is then run in separate lines to each hot water fixture. Once the water goes to the hot water tank, the only way it would be mixed again with the cold water is at a "mixing" faucet itself such as in your shower and perhaps in your kitchen sink and perhaps your bathroom sink.
If the water in your sink comes out of a single faucet, then it is a "mixing" faucet that mixes the hot and cold water inside the faucet itself. If your sink has a separate faucet (spout) for the hot water and a separate faucet (spout) for the cold water, then the water is NOT mixed inside the faucet.
Good explanation. Guess it's your call OP. If you use water from a "mixing' type faucet for drinking and the water in your water heater isn't heated high or frequently enough to prevent microorganism growth, you could end up ingesting something you don't want.
Good explanation. Guess it's your call OP. If you use water from a "mixing' type faucet for drinking and the water in your water heater isn't heated high or frequently enough to prevent microorganism growth, you could end up ingesting something you don't want.
I'm not sure that makes sense. If you turn on cold water in the kitchen sink you're not mixing anything. You're drawing it directly from the city water, according to Harry Chickpea.
Are you sure that your water heater is contaminated or this is just prevention measure?
My water heater is 37 y.o. The last 22 years (that's how long i own it) was set between "vacation setting" and 100F.
Should I fear that there is Legionella growing?
I don't think so or want to think about it.
No respiratory problems, no fevers, no Legionnaires or Pontiac disease.
Maybe you should test your water first?
Legionnaires' disease is a very small percentage of all waterborne illness. According to the CDC, about 8,000 cases of Legionnaires' disease are now reported each year in the US.
Lucky if you can get 10 years out of one where i live.
I'm not sure that makes sense. If you turn on cold water in the kitchen sink you're not mixing anything. You're drawing it directly from the city water, according to Harry Chickpea.
Not if that faucet is a single lever mixing type you aren't!
I'm not sure that makes sense. If you turn on cold water in the kitchen sink you're not mixing anything. You're drawing it directly from the city water, according to Harry Chickpea.
It is very easy to find exploded diagrams of faucets online that show how they work. If you use a mixing faucet there may be up to about a quarter cup of water that has remained in the faucet spout from a previous draw, but after that is expelled, yes, you are drawing directly from the mains if you only open the valve so that it admits cold water.
I'll point out that the anti-scald mixing valves required by code may be wherever the installer placed them. One could literally be a foot from the storage tank.
As for faucets, it is fairly common knowledge that a swab of the tip of the faucet often gives a very high bacteria count - hot water or not.
If we bring all this back out of hypotheticals and theories, tap water is not sterile, never has been, nor should it ever be so. Our bodies are designed to operate in an environment full of other life. Our gut biomes are created from what we ingest that gets past the gatekeepers of stomach acid and chyme. Sterile water gets that way with a fair amount of extra processing and care. Keeping bacteria levels low, especially e-coli levels is more an indication of general safety and proper management, and not a drive to absolute sterile water.
If you are concerned about bacteria build-up in a hot water storage tank, open up every hot water tap and run the hot water until it runs cold, and then add on another five or tens minutes of flow. The churning action of the large flow will stir the sediment and the stratification will exchange out just about all of the water in the tank along with some sediment. Stating the obvious, don't do this with a system that doesn't use a tank. You'll be waiting forever for the water to turn cold.
Now to really mess with your minds, I use water from the hot water tap to brush my teeth. As I use chlorine in my cistern, and water in there may not have had full time for the chlorine to act on it, the hot water tank not only acts as a buffer, but the chemical reactions with the chlorine act more quickly in its hot environment. For me, the hot water tap is considerably safer than the cold one. That is not a common thing.
Scenario: Turning on an electric water heater for one hour twice a week.
After doing quite a bit of research, here's my understanding of legionella bacteria in water heaters:
It grows at 68°–122° (some sources say 130° or even 138°). So the water needs to be either hot or cold, not lukewarm.
It's safest to set the tank at 140°. 120° may be hot enough to shower, but not to kill legionella. 140° is enough to scald you (not an issue for my use).
Legionella dies in 32 minutes at 140° according to studies.
So if a water heater has been off for a number of days, it would need to be heated to 140° for at least 32 minutes.
I see two potential problems with this. The first is determining exactly when the water reaches 140° at the top of the tank, where you're going to draw the water from. You could measure the temperature at the faucet to test it.
Question 1: Would 45 minutes or 1 hour be enough to be confident that you've hit
140° for 32 minutes?
The next potential problem is that during the times when the tank is turned off, cold water at the faucet will be drawn from the top of the tank, which could be in the danger zone for legionella.
My proposed solution to that: Turn off the hot and cold valves on top of the water heater after each use, so that cold water to the faucets is coming directly from the town inlet. Sound OK?
Thanks for your input!
1. The 1 hour 2x per week requirement screams for tankless.
2. The best move is to leave the the tank at around 124-127F tap temperature. Exception being if you live in a cold climate a few more degree may be needed to offset very cold - cold side water.
3. If you insist on turning the tank on and off, I've read doing so as often as you require will cost money not save money, maybe heat to 140F for an hour and then set the tank lower. The key problem here is some tanks are not easy to adjust.
I can't actually understand why i would run a water heater and then turn it off. However the EPA suggests 120. If I had any babies/toddlers I would not want it at 140 for fear of scalding.
I can't actually understand why i would run a water heater and then turn it off. However the EPA suggests 120. If I had any babies/toddlers I would not want it at 140 for fear of scalding.
I agree 140F is too hot for kids and older people.
I agree 140F is too hot for kids and older people.
Of course, which is why anti-scald tempering valves are mandated on commercial restroom sinks and often installed in apartments and residences. The hot water can be at whatever temperature - 140, 160, even higher, and the tempering valve only allows water in the distribution lines at 120 or less.
Where it can get dicey is dishwashing in a restaurant or institution. Water in a 3 compartment sink or old sanitizer can be dangerously hot.
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