Tank vs tankless water heaters

[Robert Green]

What was snipped made it very clear I was referring to not having *any* hot water if there's a problem with a tankless. Most people do not have multiple zoned hot water systems in their homes of either type so their choice is having a potentially useful reserve of (hot) water with a tank and no (hot) water reserve of any kind with a tankless.

Admittedly you can imagine all sorts of scenarios that are exceptions. Obama declares martial law or there's an earthquake and all the gas lines are turned off. Terrorists poison the reservoirs. No matter how many tankless heaters you have, you're going to be taking a cold shower without gas. If the reservoirs are poisoned, what would 50gal of clean, potable water become worth?Are those likely scenarios? No. But they're not impossible ones.

Obviously, in the world of tank v. tankless, boxers v. briefs and chocolate v. vanilla, there will be differences of opinion. In my case, I have good reasons to prefer a pilot-lit tank to a tankless. YMMV.

The tank gives me the potential of 50gal of spare (hot) water and a smaller gas line entering my home. In fact, that would be the risk I would be concerned about the most - a ruputured large diameter gas feed. There are some people who don't care about any of that and want hot water fast whenever they want it. I can wait. It's a small house and it the water heats up fast enough for me.

[Robert Green]

So true and a reminder that everyone here has a slightly different set of circumstances. You're making me think about putting a solar water heater with a gravity-feed holding system. In Scotland they've hollowed out a mountain to store water at night to store excess generating capacity of the grid. The reservoir is pumped full at night and generates extra power during peak loads by letting the water flow past a turbine.

Jeez. I've always thought it's better to lose power in the winter because (like a number of adventure films have shown) there's lots of furniture and books to burn for heat if push comes to shove. It's hard to keep cool in some areas without power, and that was one reason I was adamant about not moving us to Arizona for retirement. It was like Buffalo in reverse. That area got so cold you could get trapped in a blizzard far too easily and end up dead. Same with Arizona. What do you expect from a part of the country with a place named "Death Valley?"

It's the (very) temperate zone for me! (-:

(No hate mail from the SW or NE lovers, please!)

[Ralph Mowery]

That is another interisting question. How many tankless water heaters would it take for the same house ? Could you supply enough gas if you had a gas line or enough electricity to run tankless water heaters at one time for 3 showers?

[Al]

Most gas meters have a capacity tag on them.

In my case, I can only run 220,000 BTU at once so I'd be limited to my 120,000 BTU furnace and a single tankless water heater....which is why I don't have a tankless.

[Robert Green]

Ruh-roh! Someone's been smoking scorpion tails again!

The topic is how the tank/tankless decision plays out during emergencies and device failures. Martial law is one type of emergency that could interrupt the gas flow, like an earthquake or terrorist sabotage could. I believe the gas mains were shut off both during the infamous 14th Street riots in DC and the ones in Watts as well. Authorities know a few sledgehammered gas feeds to large businesses can burn a city down pretty quickly. However, I already admitted those are highly UNlikely (but not impossible) scenarios.

IIRC in California and Japan, gas mains are automatically shut during earthquakes to prevent massive gas-main fed fires. With tankless heaters, no hot shower for you while waiting for the gas mains to reopen. Not so with a tank heater. Maybe even no drinkable water. Clearer now?

Let me try another way: One reason I like tanks is that *whatever* kind of disaster occurs short of an asteroid strike or a nuke, a tank water heater

*might* very well provide me with 50 extra gallons of very precious and hard to find potable water stored on premises. A tankless heater has *no* means of providing *anyone* anywhere with an emergency water supply in *any* situation. Seems a simple enough concept if you're not "smoking tails." (-:

If hyperbole/humor is going to twist up your panties so much it generates an irate WTF from you, perhaps I'd better steer clear of you (and you me) until the scorpion venom leaves your system. That way I don't have to waste time explaining the obvious -- over and over and over again. As ST's venerable Dr. McCoy once said "A blind man could see it with a cane!"

So for any other "stinger smokers" out there, let's review. It's a pretty simple concept: tank water heaters *can* provide an emergency water source in a variety of disasters that tankless units simply *cannot*, no matter how many tankless units you install in a house and no matter how large, well-planned, well-sited, well-built, well-installed, well-maintained, well-liked, well-sized, well-armed or self-powered they are and no matter how hard you try to press your case because neither one holds water. (-:

It's junior high school science. Repeat after me slowly: Tank-type water heaters can store water, tankless ones can't. (-:

|-- Bobby G.

[Robert Green]

Another good reason to avoid tankless. (-: Or at least another data point to consider when evaluating the two different types of technology. FWIW, my old pilot-light gas water heater doesn't need any electricity to keep churning out hot water day after day and that's just the way I like it! What bothers me most about gas tankless heaters is the large bore supply pipe that's needed. Lots of houses blow up from gas leaks every year. A very large supply pipe increases the potential of a serious and very fast moving gas leak. No thanks!

Thanks for your input, Ralph.

[trader4]

I doubt there is much correlation between a larger gas pipe in a house and the risk of explosion. Probably more explosions are from small appliance hoses and their connections than from a supply line. And even if a 1.5" gas line started to leak, it's usually at a fitting, or maybe where some corrosion ate through a pin hole . and I'm not sure it's going to necessarily leak any more than a 1" pipe. Where it would matter would be if the whole pipe got severed and that is very rare. Even then, if it's a 1" or a 2", the result may very well be the same.

[Robert Green]

I believe that slow leaks and smaller pipes reduce the potential for a fast build-up of gas without anyone noticing the smell. I saw the results of a truck backing into a gas meter at a loading dock and remember seeing the "shadow" of the gas pouring out from the ruptured main on the ground. It was an impressive amount of gas escaping the broken pipe, but fortunately it was outside and couldn't build up to. A few years ago a similar event in a shopping center nearly knocked the entire building down just as the gas company techs were arriving on the scene. It was caught on CCTV surveillance video and it was a very impressive explosion.

I'll agree that the chances of a major rupture are small, at least in areas that don't have frequent earthquakes, but after we got shook with a 5+ quake in the DC area, an earth-quake induced rupture is not out of the question. I'd still rather have a smaller gas pipe entering the premises, just in case.

If for some reason I were to "heavy up" the gas line coming into the house, I might opt for this:

[trader4]

Small leaks do reduce the potential for a build-up of gas. But I don't think there is much, if any difference in the the size of a typical leak from a 1.5" pipe or a 3/4" pipe. If the pipe is leaking a little at a fitting, as is typically the case, probably not much difference. And chance of it somehow getting severed completely, which would make a difference, in the amount of gas released, is remote. Even then, if you have a 3/4" pipe or a 1.5 pipe spewing gas, not sue the outcome is going to be all that different either. I'd bet there are far more serious explosions and fires from the small hoses that connect dryers, stoves and such than from a large gas pipeline serving the whole house or a major appliance.

I saw the results of a

That apparently took out the gas meter and had gas spewing out from the high pressure side. Would have been pretty much the same thing with or without a tankless water heater.

It

But then you already have large service pipes entering homes and all kinds of buildings. What size service do you think goes into an apartment building with 100 people? Yet, we're supposed to worry about a slightly larger pipe to handle a tankless in a house? Where do you draw the line? Gas outdoor grill OK? Gas range? Gas ovens? Gas dryer? Gas water heaters, some houses have two? Gas furnace, some houses have two of those? Gas generator? They are all OK, but adding a tankless and suddenly it's so much more dangerous that it becomes a special consideration?

_Shut_Off_Valve/

[The Daring Dufas]

Around here most of the guys installing extra equipment at a home and the equipment requires more BTU than the existing gas lines will provide, make a call to the gas company to see if a 2psi gas service is available and it usually is. The gas meter is changed out to one that has a red dial and markings making it easy to identify it as a 2psi meter and a regulator is added to bring the pressure back down to 6-8 inches WC for the existing lines serving existing equipment. The 2psi line is tapped ahead or the regulator for the exiting gas lines and a

1/2" flexible line carrying 2psi gas is run to the new equipment where a regulator is added bringing the pressure back down to the required pressure to operate the new equipment. Most gas appliances require a pressure of 6-8 inches water column to operate but the generators I used to install required 11" WC pressure in order to run properly. When me and my late friend GB were doing a lot of remodels, it was less expensive and took less labor to install 1/2" flexible gas lines carrying 2psi to all the appliances, water heater, wall heaters and or furnace then add a regulator at the point of use. The flexible gas lines gave us a lot of flexibility (no pun) when installing equipment and making changes especially when in the middle of a remodel. I think there has been a code change requiring the thinner walled gas lines to be grounded better because a lightning strike could punch a hole in the flexible gas lines. Of course a direct hit can melt a heavy walled gas line too. ^_^

TDD

[Tomsic]

-- More stuff snipped--

But then you already have large service pipes entering homes and all kinds of buildings. What size service do you think goes into an apartment building with 100 people? Yet, we're supposed to worry about a slightly larger pipe to handle a tankless in a house? Where do you draw the line? Gas outdoor grill OK? Gas range? Gas ovens? Gas dryer? Gas water heaters, some houses have two? Gas furnace, some houses have two of those? Gas generator? They are all OK, but adding a tankless and suddenly it's so much more dangerous that it becomes a special consideration?

-- Another snip --

Seems to me that knowing how to shut the gas off quickly in an accident or earthquake would be more helpful than worrying about pipe size. Our main gas valve is outside by the meter in plain sight. It takes a hefty wrench to turn the valve which is why I keep a large pipe wrench hanging on the wall by the back door. I suppose I could also get the special tool for the street valve; but that sounds like overkill.

Tomsic

[Stormin Mormon]

Can commoners like me buy a street valve wrench for gas? I know we can get water wrenches. But gas? Some day I should pop the cover off a gas street valve, look in with a light, and see what kind of lug it has.

As to the gas shut off by the meter, they are typically greased with heavy waterproof grease. I've turned off valve by the meter with 18 inch pipe wrench.

In case of earthquake, or large fire, a gender neutral politically correct adult person of nondescript racial and ethnic origin can save a lot of people a lot of damage. Just need a good man with a pipe wrench.

. Christ>

[RobertMacy]

[Tomsic]

Getting one doesn't seem to be a problem. See:

Tomsic

[Stormin Mormon]

I've got something like that from HF, years ago. Don't think they still have the item, sadly. That does above ground meter shut off, which I can do with a pipe wrench. And "curb box valves" for water, which NYS doesn't have.

Not sure if that will work on the utility company's gas valves, under ground. Anyone know?

. Christ>> Can commoners like me buy a street valve wrench for gas?

[Robert Green]

In those cases I would suspect there would be far less potential for gas to build up in an enclosed space to explosive levels. However I do believe that in certain areas of California the main distribution feeders are protected as well as individual homes because there are underground tunnels that could fill up with gas. I am too lazy to look it up. (-:

I know Japan, specifically Tokyo, has a lot of earthquake-activated equipment designed to prevent massive fires since they can do so much damage to an earthquake stricken area. Tokyo has lots of wooden buildings spaced very close together and I've read books that talk about how bad a conflagration could be if it got really out of control on a very windy day. Got a "mate" who is a "firey" in Australia and sends me all these books. They've been having some seriously bad times with bushfires in recent years as humans move further out into the "bush."

I've also read speculation that says if a really bad earthquake hits in Tokyo Bay all of the surrounding oil and chemical plant tanks will burst and spill into the water. It will make TEPCO and Fukashima look like a bubble bath. Can't quite remember the name of that book. Something like "Ring of Poison Pearls." CRS today. )-: