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Paul Alciatore
09-01-2017, 01:52 PM
I had to flee Harvey and my town is now without water. I did not turn the gas off on the water heater when we left. Does anyone know how long it would take for a water heater tank (40 gal?) to go dry with no water coming in? I am mildly worried.

3 Phase Lightbulb
09-01-2017, 01:57 PM
You should have nothing to worry about. As the water temp rises it will expand into your inline expansion tank and that is it. Also there is a back flow valve so even if you get zero water pressure at the water main you'll still have pressure in your system.

Paul Alciatore
09-01-2017, 01:59 PM
I was not worrying about where it would go when it expands. I was worried about running about water, going dry and perhaps overheating if the over temperature controls fail. Melt down, house fire, that type of stuff.

I know the loss should be small, but even a small loss can add up to something over time. Just wondering how much time would/might be involved.

A.K. Boomer
09-01-2017, 02:02 PM
Paul I bet you will be alright for quite awhile if it's in a low spot of the house and everything drains down to it,
just what's in the heater and the upper pipes alone would probably allow for ample reserve to keep the thing from going supernova,,,

I just had a similar worry with mine, went on a week long trip and I usually always cut the water supply to the house just in case one of my old pipes shoots craps, I also forgot to turn the heater to just pilot light mode, kinda worried about it some even though my heater is the lowest thing in the plumbing I was concerned because it was so old and I gridlocked my system, I have everything shut off and then stopped the back feed to the water supply line so hydrostatically locked the plumbing with no room for expansion, do to the tank being so old I then imagined the lower part blowing out and springing a leak after a heat cycle expansion mode, then all water would be lost in a hurry and yet the tank would still be trying to heat the water, with no water the tank would overheat yet maybe not even sense it to be able to shut off...

anyways - got home and all was well but yeah was a stupid thing I did and unlike you I was not having to leave in a fury...

good luck to you hope things work out.

3 Phase Lightbulb
09-01-2017, 02:02 PM
If you have a 40 gal tank, then maybe 1/4 to 1/2 gallon (guessing at most) might expand outside. You will never loose enough water to disrupt the thermal control loop.

3 Phase Lightbulb
09-01-2017, 02:10 PM
I was not worrying about where it would go when it expands. I was worried about running about water, going dry and perhaps overheating if the over temperature controls fail. Melt down, house fire, that type of stuff.

I know the loss should be small, but even a small loss can add up to something over time. Just wondering how much time would/might be involved.

It should be fine for several years.

A.K. Boomer
09-01-2017, 02:16 PM
Again totally depends on it's position in regards to the rest of the plumbing system...

Im not positive but does not one of the lines going in or out of the tank have an internal pipe that runs close to the bottom of the tank? if the tank was higher than the main water inlet that's all it might take to percolate a little water out each heating cycle...


edit;

yes the cold water inlet is the one and that's incidentally the one that could toss it back into the dry inlet system "if" maybe the anti-back flush valve was frozen and inop. or just never installed.

they call it the cold water "dip tube" https://www.thespruce.com/anatomy-of-a-gas-water-heater-1824894

also keep in mind an un- pressurized tank will boil allot quicker and cause that unwanted percolation,,, then you got one big fancy coffee pot that gets dryer and dryer inside every cycle...

01-7700
09-01-2017, 02:17 PM
You have nothing to worry about from your water heater friend - hope you are able to resume life as you knew it soon.

H380
09-01-2017, 02:33 PM
The gas valve has a built in high water temperature "Fuse". I have a 12 year tank 40 Gal Whirlpool that if I don't drain every year. The buildup from the anodes corroding falls on the bottom of the tank. It will bridge the gap between the temp probe and bottom of the tank and overheat the gas valve and it closes the gas valve. It is permanently closed. The only way to fix it is to put in a new gas valve.

A.K. Boomer
09-01-2017, 02:55 PM
H380 does my tank have that? My tanks a 1983!!! have no idea how it's still making it but works like a charm...

H380
09-01-2017, 03:09 PM
Yep it should. The gas valve screws in to the tank. It has a SS probe that looks like a commercial thermometer. I am on my 3rd as you can see.

https://i.imgur.com/EazVYxP.jpg

3 Phase Lightbulb
09-01-2017, 03:12 PM
Unless your heating your water with an open bucket over a fire, the system is closed and can't vent/expand anywhere except into an expansion tank on the hot-water side. Even when it "expands" the hot water tank is still full of water -- the volume just increased a little bit due to the temperature then returns back into the tank as it cools down.

A.K. Boomer
09-01-2017, 03:38 PM
Don't know about Paul but me no gots an expansion tank...

3 Phase Lightbulb
09-01-2017, 03:54 PM
Do you have a well pump and a pressurized holding tank? If you're on city water, you should also have a check-valve preventing back-flow into the city supply. Without an expansion tank, you're just putting stress on your plumbing system every time the water in your heater thermally expands then contracts as it cools off. If you have air in your system then this acts like an expansion tank.

A.K. Boomer
09-01-2017, 03:58 PM
This is a very old system - iv looked for long standing vert. pipe thats a dead end and would be used to hold air but have never seen any of it,

im on city water...

Paul Alciatore
09-01-2017, 04:36 PM
House is single story, on a slab. No basement. The heater is in a storage room, off the garage and that room is at the same level as the rest of the house. The garage is about 4-6 inches lower. As on all water heaters I have ever seen, the hot and cold connections are at the top. I don't know how they work on the inside.

It is a new heater, about six months old so it should be in good condition.

I am in the city and I do have city water. But as I said, the whole city is without water and will probably be that way for several days.

3 Phase Lightbulb
09-01-2017, 04:41 PM
Just know that you will have a full tank of hot water when you get home. And if the city water supply is back on then you'll be able to take a nice long shower and wash all of that worry away.

old mart
09-01-2017, 05:24 PM
Things would only be bad if the gas was set to boil the tank, or if the water drained out. The gas heater will have built in safety features anyway.
It reminds me of the end of "Around the world in eighty days".

Weston Bye
09-01-2017, 05:34 PM
A phone call to police/fire/power/gas supply/somebody might get someone to go out to the house with a crescent wrench and turn off the shutoff valve at the gas meter or tank.

3 Phase Lightbulb
09-01-2017, 05:42 PM
A phone call to police/fire/power/gas supply/somebody might get someone to go out to the house with a crescent wrench and turn off the shutoff valve at the gas meter or tank.

Why would he want to do that? He won't be able to take a hot shower when he gets home. Instead, he'll have to call someone to check/purge his gas lines of air and turn the gas back on.... Major PITA

Weston Bye
09-01-2017, 06:25 PM
Why would he want to do that? He won't be able to take a hot shower when he gets home. Instead, he'll have to call someone to check/purge his gas lines of air and turn the gas back on.... Major PITA

Yep, but it would be his choice as to which hassle to deal with, and depends on what he is comfortable doing for himself. I would never "call someone" to check/purge .... Indeed, I will be doing that very thing tomorrow, to install a new dryer at a relative's house. "to check/purge" a gas line is just not that big a deal, for most people I know.
"He won't be able to take a hot shower when he gets home." Small price to pay for peace of mind until he gets home.

PStechPaul
09-01-2017, 07:51 PM
I thought you were worried about flood waters rising above the base of the water heater. In that case, I think it would extinguish the flame and cool off the flame sensor so it would need to be reset. Not having a water supply is probably not a problem, as discussed above. It may even be that the gas supply might be cut off (as well as electric), until the emergency is over.

J Tiers
09-01-2017, 08:27 PM
Don't know about Paul but me no gots an expansion tank...

No such here either. No expansion tank, no one-way valve. Our tank would expand and push water back into the city water system. House is just under a hundred years old, and the first water heater in here was probably coal fired. Part of the shop is in the old coal bin.....

none of that newfangled stuff to go wrong here.

lakeside53
09-01-2017, 08:32 PM
We had the same thing until 10 years ago when we had flat rate un-metered water. When the meter was put in it contained a soft seat check valve (not a "rated" back flow preventer) to stop gross push-back. We were told to put in an expansion tank. Dead easy.

johansen
09-02-2017, 02:50 PM
No such here either. No expansion tank, no one-way valve. Our tank would expand and push water back into the city water system. House is just under a hundred years old, and the first water heater in here was probably coal fired. Part of the shop is in the old coal bin.....

none of that newfangled stuff to go wrong here.

well if you don't have a one way valve at the city water line, sure.

most people do, and without an expansion tank, water heats up and forces its way out of the pressure/temperature relief valve on the hot water tank. eventually this causes the valve to fail and it will constantly leak water.

not to mention the 150 psi needed to open the valve. that may be enough to burst failing pipes/valves..

lakeside53
09-02-2017, 04:44 PM
Yes, and as the temp/pressure relief valve often vents to the outside, you may not know it's happening.

Baz
09-02-2017, 05:21 PM
Does you main jet even come on without mains electricity? I'd think if the water is off the electric could well be too.

J Tiers
09-02-2017, 05:51 PM
I have put in some air chamber type anti-water-hammer devices, which have some expansion capability. Basically a length of pipe stubbed off near the local valve. Need to put in more, still have some hammer.

The hot water heat system has a big air tank on it, for obvious reasons. Not the incoming water.

Paul Alciatore
09-02-2017, 08:07 PM
Water is OFF. Electricity is ON and, as far as I can tell, has been for most if not all of my absence. My house DID NOT FLOOD and I believe that danger is past, at least for this storm. I was smart enough to look at a topographic map BEFORE I bought it. For my city, which is relatively flat, it is on high ground and the neighborhood has good drainage.

I was only worried about a number of heating cycles causing small amounts of water to boil off and after a period of time, with no water supply, it could become empty. I think all the comments here have eased my mind.

I am sitting in a motel in northern Texas, watching Google Maps for the road conditions and waiting for the water to be restored. Can you say "boring"!

dbq49er
09-02-2017, 08:37 PM
I thought you were worried about flood waters rising above the base of the water heater. In that case, I think it would extinguish the flame and cool off the flame sensor so it would need to be reset. Not having a water supply is probably not a problem, as discussed above. It may even be that the gas supply might be cut off (as well as electric), until the emergency is over.

Finally somebody gets it, The only issue here is did the water flood the bottom of the water heater and snuff out the pilot flame, at which time the thermal couple would cool and shut off the gas supply at the valve. Many people go away for weeks on vacation and do nothing with their water heater and there fine. I have only seen expansion tanks on hot water base board heating systems. Water lines have hammering arresters installed to stop the pounding when washing machines or dishwashers have there valves suddenly stop the flow of water.

PStechPaul
09-02-2017, 08:51 PM
The water hammer arrestors eventually fill with water due to air dissolving into the water. They need to be repressurized from time to time to remain effective. A one-way valve like a valve stem on a tire might work, and then you can blow air into the system with a compressor. Or just an ordinary valve opened with the system shut off and allowed to drain a bit. Otherwise a pressure tank with a rubber bladder, as used with well pumps, would be ideal, and not very costly.

https://www.amazon.com/Water-Hammer-Arresters/s?ie=UTF8&page=1&rh=i%3Aaps%2Ck%3AWater%20Hammer%20Arresters

https://images-na.ssl-images-amazon.com/images/I/41ZTVwXI4IL._AC_US218_.jpg

https://www.amazon.com/dp/B00Q798N8E/ref=sxr_pa_click_within_right_2?pf_rd_m=ATVPDKIKX0 DER&pf_rd_p=3163805422&pf_rd_r=MDSTXCTFFSZXDYC9KH0M&pd_rd_wg=cZECK&pf_rd_s=desktop-rhs-carousels&pf_rd_t=301&pd_rd_w=hAmkI&pf_rd_i=Well+Pressure+Tank&pd_rd_r=RW81D9ZP6CZNNRJM77R1&psc=1

https://images-na.ssl-images-amazon.com/images/I/71iiFnPyy5L._SL1500_.jpg

J Tiers
09-02-2017, 11:56 PM
I just drain them every so often. And, some are located so they refill with dissolved air that comes out of solution at or near high spots.

I have some of the bladder or piston ones as well, but they are generally copper, so they require a dielectric union to connect to the iron pipe.

This type is brass, which typically needs no fancy union. Not bad on price, either.

http://www.homedepot.com/p/Quiet-Pipes-1-2-in-x-1-2-in-Low-Lead-Brass-Pipe-Thread-x-Pipe-Thread-Water-Hammer-Absorber-39177/202078129

However, only the larger airspace type will dual function as expansion chambers, the others will be rapidly overcome

gellfex
09-03-2017, 12:10 AM
Finally somebody gets it, The only issue here is did the water flood the bottom of the water heater and snuff out the pilot flame, at which time the thermal couple would cool and shut off the gas supply at the valve.

I recall reading that if that happens the new combustion safety system they put in some years ago is shot and you need to replace the heater.

Paul Alciatore
09-03-2017, 12:48 AM
Paul,
I have heard that and I understand the idea and the science behind it. But I think there is more to it. I have a long water run to one toilet in my house. And when the water cut off, it always produced a bang in the pipe. Not a quiet little bang, but a big bang, like someone hit the pipe hard with a hammer. I guess that is why they call it hammering. I installed an air chamber like the one you showed. It did nothing. It was a big bang. So I made a larger air chamber with pipe and fittings. It held five or six times as much air as the puny one you show. And presto, no more bang; not even a quiet one. Gone. And it continued to work for years. Never again was there any noise what so ever from that pipe.

So I can only think that there is something else at play here. Perhaps some dissolved gases are coming out of the water and getting trapped in the chamber. Perhaps this is due to the lower temperature because it's in an air conditioned house. Or perhaps it takes decades for the air to dissolve - several decades. All I know is it did completely cure the bang for years and years.




The water hammer arrestors eventually fill with water due to air dissolving into the water. They need to be repressurized from time to time to remain effective.
...<snip>...

PStechPaul
09-03-2017, 04:13 AM
It could also be that there is a sharp turn in the pipe after a long straight run, and the inertia of the long column of water causes the pipe to flex and perhaps hit something nearby. I've never had a problem with water hammer, so no direct experience.

lakeside53
09-03-2017, 11:05 AM
Water hammer (hydraulic shock wave) happens even if you don't "hear" it. Your dishwasher and washing machine are primary culprits, as are temperature/pressure regulating shower valves. Small "hammer arresting" devices, often have a piston and o-ring seal; some of course are just dead-ended pipes. You typically need to place these at the problem source - not just "per house". An expansion tank might help hammer, but not if some distance away from the problem (large house).

I retrofitted 12 inch tall dead-ended pipes to stop my regulating shower valve from destroying my pipes (it sounded like a non-stop woodpecker) - no problem for 25 years.

A.K. Boomer
09-03-2017, 12:19 PM
in regards to water hammer, for some reason I don't have the "condition" and cannot find any real reason as to "why not" because I have long straight runs ending at things like toilet shut offs - washer shut offs and other mechanical or solenoid controlled devises that abruptly close off large quantities of water, yet I have no buffering systems.

One of the reasons not mentioned might be the fact that I have large pipe feed holes in the flooring where the pipes go from being horizontal to then being vertical,,, if your systems don't have this and the pipe is just 1/16" or 1/8" away from the wood flooring and esp. if that clearance happens to be on the momentum side then you can really amplify the waterhammering effect 10 fold as the pipe itself will physically connect with the house flooring... it could also add a real fast acting woodpecker effect, just something to be aware of,




I have heard mild hammer but it's such a non-issue and so infrequent I cannot even tell you what makes it happen - and when it happens it's "lazy" sounding - very elastic and not abrupt. mine is just pipes that's for sure and not getting any of the house involved...

J Tiers
09-03-2017, 11:48 PM
That might actually stress the pipes more than if they were restrained, even though it SOUNDS worse when they bang on things. When restrained, they do not move as much, and presumably do not have as much bending applied to the pipe joints.

MattiJ
09-04-2017, 03:32 AM
in regards to water hammer, for some reason I don't have the "condition" and cannot find any real reason as to "why not" because I have long straight runs ending at things like toilet shut offs - washer shut offs and other mechanical or solenoid controlled devises that abruptly close off large quantities of water, yet I have no buffering systems.

Worst-case scenario is open-ended long pipe connected AFTER quick operating valve. Quickly acting tap or valve at the end of pressurized pipeline is mild compared to that.

A.K. Boomer
09-04-2017, 09:30 AM
Matt that sounds like a recipe for cavitation so can only imagine all the weird forces happening with that,

but aside from me operating my house shut-off valve fast I cannot think of any places where I have a situation like that in my plumbing...

JT would depend on what type of plumbing and how it's connected at the end of it's vertical runs, I could see trying to keep it contained with the floorboards being really hard on one particular joint also - the first one to take off and run vert. is going to go through allot of hell,

If someone is experiencing water hammer on the hot side and only after letting the water run a little it might be worth checking into this clearance issue, long runs of pipe might have ample room for clearance normally but heat a piece of 20' long copper up over 100/120 degree's F and that clearance will get eaten up pretty quick...

Paul Alciatore
09-04-2017, 12:27 PM
Yes, long run of pipe and water is flowing fairly fast to fill the toilet tank. It is shut off fairly quickly by the float valve but that mass of water is still moving so energy is stored in it and has to go somewhere. Inertia.

I understand that some modern toilet valve mechanisms have a slow shut off feature to prevent this. It must be a somewhat common problem. I did not know that such valves were available when I installed my super sized air chamber.

3 Phase Lightbulb
05-03-2019, 06:23 PM
Unless your heating your water with an open bucket over a fire, the system is closed and can't vent/expand anywhere except into an expansion tank on the hot-water side. Even when it "expands" the hot water tank is still full of water -- the volume just increased a little bit due to the temperature then returns back into the tank as it cools down.


Don't know about Paul but me no gots an expansion tank...


No such here either. No expansion tank, no one-way valve. Our tank would expand and push water back into the city water system. House is just under a hundred years old, and the first water heater in here was probably coal fired. Part of the shop is in the old coal bin.....

none of that newfangled stuff to go wrong here.

That's funny :)

J Tiers
05-03-2019, 11:26 PM
That's funny :)

You probably think so. You would.

You also resurrected an ancient thread.

Back in another city when I was a kid, the city decided to require backflow valves. But that was before expansion tanks were a "thing", and the city did not require them. naturally, a lot of HW tanks were destroyed, and the city took out the requirement. But the tank we had was destroyed, and it was a monel tank that would have lasted a century if the $#@! city had not required the valves. When the tank was replaced, the valve was removed.

Just had the tank here replaced. It now has an expansion tank. There may or may not be any valve as part of the water meter, no info on that, the old HW tank lasted 22 years, so there was no big problem. If there is a valve, then when (not if) the tank bladder fails, the expansion tank will fill with water, and become worthless, at which time we may have an issue with the HW heater. There is nothing on the expansion tank to show whether or not it is working.

New thing is the water pressure, which if over 80 psi has to have a pressure regulator. I measured ours at 95 PSI, which the plumbers also found. But the next street over had 70 PSI a year ago, and they are on the same pipes. Something does not seem correct with that. Either the pressure went up 25 psi, or the two streets are very different..... although we are on a hill, accessible from only one side, so there is just one pipe supplying water to this area.

A.K. Boomer
05-03-2019, 11:43 PM
My tanks a reliance 1987 --- so 32 years not to shabby - im hoping for another happy 32 more...

alanganes
05-04-2019, 09:28 AM
But that was before expansion tanks were a "thing", and the city did not require them. naturally, a lot of HW tanks were destroyed, and the city took out the requirement.

Not many systems around here have expansion tanks on the HW lines, at least not older systems. Maybe for new construction. Every HW tank does have a "T&P" (temperature & pressure) relief valve that is supplied with the tank. So any excessive pressure just blows water onto the floor (messy) or down a drain, outside of the building or whatever They also have a vacuum break valve that allows the tank to suck in air if for some reason water is drawn out with nothing flowing in to replace it, to prevent the tank from buckling in under vacuum.

plunger
05-04-2019, 09:37 AM
Not many systems around here have expansion tanks on the HW lines, at least not older systems. Maybe for new construction. Every HW tank does have a "T&P" (temperature & pressure) relief valve that is supplied with the tank. So any excessive pressure just blows water onto the floor (messy) or down a drain, outside of the building or whatever They also have a vacuum break valve that allows the tank to suck in air if for some reason water is drawn out with nothing flowing in to replace it, to prevent the tank from buckling in under vacuum.

In my country geysers or tanks are made from steel so thay cant collapse through vacuum. But we still need two vacuum breakers .One on the cold to prevent back syphon through the anti syphon loop or else the tank would burn its element out if theres a water failure shut off. The vacuum breaker on the hot facilitates draining ,otherwize the water would just stay in the tank.We dont have expansion tanks but have relief valves which constantly drip. No potable water is ever allowed to be fed back into the main system.We also have tp valves on our geysers. Its a criminal offence to install a geyser incorrectly but there are no geyser police. But people do die every year from incorrect installations.

3 Phase Lightbulb
05-04-2019, 10:28 AM
I'm thinking of replacing our water heater in our main house (large 80 gallon propane) with an equivalent sized electric on-demand system. We have a 400 amp service and the SE panels are in the same utility room as my hot water heater so powering one is nice and convenient. In our new beach house we have a propane fired on-demand hot water heater which works really well but it does seem to take a full minute or so before hot water comes out. I'm thinking a well designed electric on-demand system of sufficient capacity could replace my 80 gallon water heater.

Tankless 199K BTU propane fired on-demand water heater in our beach house:

http://www.bbssystem.com/pictures/tankless1.jpg

http://www.bbssystem.com/pictures/tankless3.jpg

A.K. Boomer
05-04-2019, 10:52 AM
I guess i have 3 dates on my heater - 1983 1987 and 1988 --- it looks like the 83 is it's efficiency rating year or something and the 87 is year built and 88 is year installed (scratched into the paint)

I really like the newer gas heaters that shut down the vent, these old ones may be insulated on the sides but they just bleed heat constantly in fact they create draw just with their own heat so accelerate the process,,,

still - it's hard to justify it until this one shoots craps cuz I have gas heat, gas hot water heat, gas cook stove and gas cloths dryer and what's my monthly gas bill? 15 bucks a month spring summer and fall and maybe 30 max in winter if I get a little lax with the wood burning... lol

3 Phase Lightbulb
05-04-2019, 12:10 PM
I guess i have 3 dates on my heater - 1983 1987 and 1988 --- it looks like the 83 is it's efficiency rating year or something and the 87 is year built and 88 is year installed (scratched into the paint)

I really like the newer gas heaters that shut down the vent, these old ones may be insulated on the sides but they just bleed heat constantly in fact they create draw just with their own heat so accelerate the process,,,

still - it's hard to justify it until this one shoots craps cuz I have gas heat, gas hot water heat, gas cook stove and gas cloths dryer and what's my monthly gas bill? 15 bucks a month spring summer and fall and maybe 30 max in winter if I get a little lax with the wood burning... lol

Tick..... tick....... tick..... tick...... tick...... tick.....

A.K. Boomer
05-04-2019, 12:51 PM
it's true - just so it doesn't happen when im on vacation or something - would be a fine time to find out the sump pump quit working lol

wmgeorge
05-06-2019, 08:22 AM
I guess i have 3 dates on my heater - 1983 1987 and 1988 --- it looks like the 83 is it's efficiency rating year or something and the 87 is year built and 88 is year installed (scratched into the paint)

I really like the newer gas heaters that shut down the vent, these old ones may be insulated on the sides but they just bleed heat constantly in fact they create draw just with their own heat so accelerate the process,,,

still - it's hard to justify it until this one shoots craps cuz I have gas heat, gas hot water heat, gas cook stove and gas cloths dryer and what's my monthly gas bill? 15 bucks a month spring summer and fall and maybe 30 max in winter if I get a little lax with the wood burning... lol

Same here. Hard to justify a tankless on demand when your bill for heating water is $20 or less per month. It makes more sense to insulate the tank more to hold the heat in, once its up to temp.

If I cut my water heating cost in 1/2 ;) it would take how many years to pay off the difference?

PS When I am gone on vacation, I turn off the main water valve. WH leaks no big deal, I also have a ball valve shutoff on the cold water feed to the WH. Leaking, turn off until its replaced.

Bob Engelhardt
05-06-2019, 07:25 PM
In my country geysers ...

geyser: a gas-fired water heater through which water flows as it is rapidly heated