Water heater question

[Frankies Girl]

We just replaced our 22+ year old gas water heater. Got same tank/gas heater as replacement, and have it set to "A" temperature which is a bit hotter than the required setting by the installer (we got the "I can only set it to this, you can adjust it to whatever you'd like, but I'm legally not allowed to make this any hotter" speech. It is set to heat the water to a safe temp that will not scald, but also high enough to kill any possible bacteria).

It is installed in a uninsulated garage, in the U.S. Gulf coast area, meaning we may see some mild cold temps, and occasionally even a small freeze, but in general our winters are not wintery, just cold-ish. We don't do wraps or anything to the water heaters in my area. I had a competent, reliable plumber I've used forever install it, and it is a decent brand/sizing for our house. There appears to be no issues with the unit or install itself.

For the old unit, we'd been occasionally setting up the temperature during winter due to the hot water just not being all that hot - it would be pretty warm but the husband and I both like HOT showers/baths, so we'd just turn it up a bit, wait and then get a reasonably decent temp for the ablutions and then go dial it back to the recommended setting.

BUT new water heater? It seems like we may need to dial it hotter temperature a bit before bathing just like the old one. We don't even need to turn on any cold water when bathing - it's warm enough but not steamy hot, and cold water would just make it not that comfortable for us. Which is odd, but I'm wondering if the fact that we take showers/baths every other day in general and rarely use hot water otherwise (we do have a dishwasher, but don't use much hot water).

Could this be because we don't use lots through the day so it's mostly not having to cycle on/off to keep the water hot?

Should we just set the temp hotter and leave it, or just do like we used to do and set it hotter on the dial about 15 or so minutes before we plan on bathing so we get a decent amount of HOT water?

[Sibley]

I was told that "A" wasn't hot enough to prevent all the nasty stuff from growing, so mine is one step up. It is plenty hot. Too hot for me really, but I'm sensitive in general to that sort of thing. It's not hot enough to burn I don't think, despite what it feels like to me. And it doesn't actually cost much more than the A setting.

Are your pipes insulated? Even before my water heater setting got changed, wrapping the pipes with the cheap foam stuff did make a noticeable difference.

[Frankies Girl]

No pipe insulation either. They run them through the unheated attic space in my area, and that was all kinds of fun during the hard freeze in Texas early this past year when the power grid also failed and left most of the state without power. I lucked out and decided to drain our lines and opened up the taps so we didn't have any major damage but lots of houses in my neighborhood had busted pipes that took out their entire house (since they were spraying from the ceiling, it caused extensive water damage from the top down).

I may go ahead and bump it to B and see how that works out. I don't worry about the extra costs on the gas, but I just want to make sure I am not damaging the water heater or doing something dumb by keeping it set up higher than the recommendation all the time.

[Abe]

The recommended temperature setting is to prevent children from burning themselves when playing with water taps. You won’t damage the heater.

[sonofsven]

Set the temp hotter and leave it. Compare your NG bill over a few months to see any increased consumption cost.
Mine does this sometimes. I think it's a cycling issue; the water is just warm enough to not trigger the burner but once I try to fill the tub it can't quite keep up with demand. If I run the hot water in the kitchen sink first thing I can hear the WH start and then by the time I fill the tub there's more hot water in the tank.

[SunnyDays]

You can safely set it to whatever temperature you want without damaging the tank, it will just cost more to turn it up.  Personally, I would rather pay a bit more than have to even think about fiddling with the dial.  I've never moved mine from whatever the initial setting was, and it's been fine for many years.

[NorCal]

Turning it up will be fine.

It’s still probably worth insulating the hot water lines. It’s stupid cheap to do (probably less than $20, depending on the length of your pipes).  It won’t be life changing, but it can make marginal difference in comfort and energy savings for a tiny investment.

[Fomerly known as something]

Also likely worth it to wrap the tank again something like a $20 add.

[Abe]

Be careful with wrapping the tank itself - modern heaters have more than enough insulation and if you cover the inlet or outlets inadvertently, it can reduce efficiency and/or start a fire. If the tank is cool to the touch you don’t need to wrap it.

[Spiffy]

Since it was installed by a professional in your garage, it was probably done safely, but just want to check because a family member had a terrible accident where the water heater was in their garage directly on the floor and their child was playing in the garage and knocked over a gas can near the gas water heater. It caught on fire and killed the child. Such a horrific accident. So please make sure yours is safe!

[Frankies Girl]

Thanks for the help/suggestions everyone!

Just to clarify: definitely done professionally/well/right as far as the install. It is required by our state law to be 18 inches off the floor, it's in a garage so it's concrete floor and not inside the house or near any of the sleeping areas. The garage door to the outside isn't air tight either so that's a good thing for ventilation. No kids in the house (2 adults only).

We went ahead and turned it up to B and so far, so good. I looked into the actual temp setting after posting this, and it does make me feel better knowing that the water is 130˚F at A and 140˚F for B and that definitely makes it hot enough to be happy with any bath/shower and kill off any bacteria to boot.

If it adds an extra $5-$10 a month to our gas bill, I think I'll be okay with being so decadent.

[Abe]

Thanks for the help/suggestions everyone!

Just to clarify: definitely done professionally/well/right as far as the install. It is required by our state law to be 18 inches off the floor, it's in a garage so it's concrete floor and not inside the house or near any of the sleeping areas. The garage door to the outside isn't air tight either so that's a good thing for ventilation. No kids in the house (2 adults only).

We went ahead and turned it up to B and so far, so good. I looked into the actual temp setting after posting this, and it does make me feel better knowing that the water is 130˚F at A and 140˚F for B and that definitely makes it hot enough to be happy with any bath/shower and kill off any bacteria to boot.

If it adds an extra $5-$10 a month to our gas bill, I think I'll be okay with being so decadent.

Sounds good. One last thing to keep in mind - if you have any visitors with diabetic neuropathy, they may not feel how hot the water is with their feet and can get severe burns. Not a common situation, but it can be very bad if it happens. Recommend turning it down if such a visitor comes.

[alsoknownasDean]

According to this, it needs to be over 60C/140F to kill legionella bacteria, but there's also a point of view where it needs to be set to 49C/120F to reduce the risk of scalding.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/

I hear modern electric hot water heaters keep their tanks at around 50 with a short blast above 60C to kill the bacteria, but I don't think that's possible with gas. My gas heater has a recommended setting for over 60C.

Although here it's more common to put the water heater outdoors.

[yachi]

According to this, it needs to be over 60C/140F to kill legionella bacteria, but there's also a point of view where it needs to be set to 49C/120F to reduce the risk of scalding.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/

I hear modern electric hot water heaters keep their tanks at around 50 with a short blast above 60C to kill the bacteria, but I don't think that's possible with gas. My gas heater has a recommended setting for over 60C.

Although here it's more common to put the water heater outdoors.

Good design calls for a mixing valve between the tank and the faucet when using temperatures this high.  The mixing valve combines the scalding water tank water with a measured amount of cold water.

I'm not sure how a short blast to 60C could be "short", as water heaters have a lot of volume and insulation.  I imagine 150 Liters / 40 gallons in an insulated tank would take a long time to cool back down.

For what it's worth, most legionella outbreaks have occurred in large buildings, they say it's perhaps because complex systems allow the bacteria to grow and spread more easily.

This source:
https://specialpathogenslab.com/legionella-in-homes/
states it's rarer to contract it from the shower in your home, but humidifiers and whirlpool spas can be a source.  I've taken to boiling the water I use for my CPAP as it acts somewhat like a humidifier.  I wasn't really thinking Legionnaires, just that sometimes I didn't feel the greatest shortly after waking up.

I suppose it would not be a bad idea to periodically raise your hot water system super hot, and flush out all your hot water pipes, with the intent to kill any colonization.  Then return the system to normal.  I wonder what sort of frequency would be effective while keeping operating costs low.