# Water Heater Bursting?



## Illum (May 24, 2006)

um....regarding this: http://www.electrical-contractor.net/The_Store/Cr/RPlumb_Insp_Back.htm


Our tank water heater was newly installed about over 1 year ago.


We are leaving on a vacation and mom, out of no where, begin fearing the water heater will blast off like a rocket....

I have found few info on the event, none on maintaining and avoiding the event from occuring....any suggestions here?


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## yuandrew (May 24, 2006)

Water heaters are suppose to have a T&P safety valve to vent excessive pressure if something like that would happen. Unless whoever installed the water heater plugged the hole where the T&P valve would go with a capped off peice of pipe;  :help: I don't think there should be too much of a problem.

If she is really paranoid; tell her you're going to shut off the gas or electricity to the heater, shut the water off to the house and drain the tank so that there's no water pressure inside. :naughty:


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## DUQ (May 24, 2006)

If a T&P valve doesnt get tested once a year, it can seize and fail. You should always close the main water valve when you are away for extended amounts of time.


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## BIGIRON (May 24, 2006)

The cold water line into the wh should have a valve on it. Just close it and set the thermostat to off (if gas) or flip the breaker(s) to off if electric. You'll have to relight the pilot (or maybe you have elec ignition if only a year old) or reset the breakers when you return.

Leave the popoff valve closed. 

Enjoy your trip.


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## cobb (May 24, 2006)

I recall that famous clip they show on the history channel when they air bathroom tech. THe hot water heater exploses like a rocket several feet hundred into the air. I actually knew a couple who had a mini one in a small bar they were setting up in a restaurant. Somehow it was not setup right and EXPLODED. They said it looks like a bomb exploded in the middle of the place and it was just ruined.


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## raggie33 (May 24, 2006)

just recall what hot water does it can move a locotmotive steam is amazeing


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## jason9987 (May 24, 2006)

water heaters can violently explode but its very rare and if it did happen you would be lucky if it happens while your on vacation cause then you wont get killed. I'm a vouluteer firefighter and we just had a call for that happening last night but its the only time it ever happened in our fire district and it is very rare. But the one we had would have killed anyone if they were in the basement, thank God no one was. it damaged the entire foundation of the house an shot pieces of glass from basment windos through the garage door. But many things must go wrong at the same time for this to happen, the gas needs to get stuck on and two pressure realease safetys need to fail, and the tank need to be strong enough to build up enough pressure to explode rather and tear apart.


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## James S (May 25, 2006)

Jason has the right idea, it's very rare. Most water heater failures just cause leaking.

But you SHOULD be pulling the pin on the T&P valve (thats Temperature and Pressure) once a year and you should also drain a buckets worth of water our the bottom tap once a year to remove sludge.

If it's been many years since you've done any of this then have more buckets handy as the valves may not want to close all the way if they are gummed up... Worst case you'll have to run turn the water off and call a plumber to replace them.

I've seen pictures of installs where in order to fix a leaky T&P valve the homeowner has just screwed a cap on the pipe!!! Dont do anything like that...

much more dangerous would be flue problems from gas water heaters. Make sure your flue is installed properly and not sagging or running downhill or running into the wrong kind of chimney and all that stuff.


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## C4LED (May 25, 2006)

Are electric water heaters safer than gas heaters?


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## raggie33 (May 25, 2006)

gas vs elctric for safety id say no other then electric wont emit carbon monoxide.but im no expert so dont listen to me lol


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## dfred (Nov 8, 2007)

Mythbusters on the Discovery channel tonight (on right now in PST) is doing their main myth on catastrophic water heater failures due to multiple failures in the safety devices...

(I can't believe I remembered this thread.  )


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## Aaron1100us (Nov 8, 2007)

Just get a tankless water heater. No tank to explode. Our water heater is old and I'm thinking about replacing with a tankless one. Not for that reason but because they are supposed to be more efficient. They do take a little bit longer to get hot water and are pretty expensive. Still investigating them.


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## Avatar28 (Nov 8, 2007)

Aaron1100us said:


> Just get a tankless water heater. No tank to explode. Our water heater is old and I'm thinking about replacing with a tankless one. Not for that reason but because they are supposed to be more efficient. They do take a little bit longer to get hot water and are pretty expensive. Still investigating them.



My favorites are the point of use water heaters. Just a couple of seconds to get hot water and they should be even MORE efficient than the tankless ones.


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## chmsam (Nov 8, 2007)

Read the manual that came with the water heater, check for on line manuals/help, or call a plumber. Most hot water manufacturers now have on line manuals or safety sheets that should allow you to safely setup, maintain, set for vacation, and drain water heaters. 

There are usually also instructions for checking the T&P valve but use caution since even "low" settings on water heaters can produce water hot enough to cause burns. 

Electric and gas water heaters can be quite different in their maintenance. Air in any hot water system can be very bad. Proper setup, operation, and maintenance is much better than a flooded basement and no hot water, and it's usually not that much work. 

Basically, don't assume or guess about the maintenance, just find out to be sure.

And never trust a brother in law who says he knows what he's doing.


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## Avatar28 (Nov 8, 2007)

chmsam said:


> And never trust a brother in law who says he knows what he's doing.




Uh oh. I had TWO brothers in law help me install mine.


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## BB (Nov 8, 2007)

I was the son-in-law that installed my In-Laws' new water heater the last time (hmmm, probably getting near time for a new round of installs around the various family homes).

Been there, done that...:shakehead

-Bill


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## will (Nov 8, 2007)

one thing about turning off the cold water supply prior to the heater. If you do - open a hot water tap somewhere. closing the cold water supply will make the system closed, nowhere for the pressure to go if the pressure valve is not working..


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## Valpo Hawkeye (Nov 8, 2007)

Aaron1100us said:


> Just get a tankless water heater. No tank to explode. Our water heater is old and I'm thinking about replacing with a tankless one. Not for that reason but because they are supposed to be more efficient. They do take a little bit longer to get hot water and are pretty expensive. Still investigating them.



Lots of work to install and way more parts to maintain. Also, the heat exchanger must be flushed at certain intervals, usually every year, but depending on your water quality, it can be more often. They are "green" but they sure do cost some "green", as well. Most use a stainless steel flue, need an upsized gas line, and are often (though not necessary) moved to an outside wall. 

As for the main discussion, it's VERY rare that a water heater explodes. Several things have to go wrong concurrently...

Oh, and I always turn off my water when leaving the house for anything longer than a day! You never know. I'm a licensed plumber, and I've had to repair some pretty catastrophic leaks before. An ounce of prevention...


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## BB (Nov 8, 2007)

Valpo,

Have you seen any "green" tanked natural gas water heaters?

I have found one (can't find the link/model right at the moment)--but it was really designed for use in a restaurant type setting (instant hot water and high water rate demand)--it had forced air and the inlet/exhaust where at the bottom (so that there would not be a continual "breeze" up the chimney cooling the water column).

I would have thought that there would be options out there now (say a 10-40 gallon tanked heater with forced air combustion).

I have used tankless heaters before--overseas--but they tend to be a pane in the rear end to get a stable shower temperature (the newer one of my in-laws would turn off and I would have to stop and start the water a few times to get it working right again). And anytime you stop/start the shower--the dance starts all over again (plus you have to keep the water flow relatively high for them to turn on in the first place--typically 1/2 gpm or more).

-Bill


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## Valpo Hawkeye (Nov 8, 2007)

Yeah, some of the tankless use a small water-powered generator to handle the intermittent pilot. As for the "green" water heater, no, I'm not sure. They used to use a flue damper to prevent a natural draft from cooling the tank, but they don't allow those in my state any longer. A power-vented water heater will essentially do what you described. However, they're not sealed combustion. I'd be interested in a link to the product if you can find anything.


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## yuandrew (Nov 8, 2007)

> Have you seen any "green" tanked natural gas water heaters



AO smith has a 90+ efficiency lineup called "Vertex" as well as some sealed combustion power vent models.


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## BB (Nov 8, 2007)

Looks like Yuandrew beat me too it...

Here is one link (A.O. Smith Residential Closed Combustion Tanked Heaters and other types) I had looked at long ago--either they have more models now, or I did not look closely the first time.

I am going look through the specs. and see what pops up.

Also interested in your professional opinion too Valpo.

-Bill

PS: Looks like a standard gas water heater is around a 0.6 heating factor, 0.8 is considered the minimum for a Fed Tax Credit, and at least one of the closed combustion models (tanked) is 0.9.... Not bad. Need 120 VAC to run the fan and igniter--no hot water during long power failures.

PPS: Yes, it looks like the Vertex (link to PDF file) is the only true high efficiency tanked water heater on this page.. 90% efficiency rating, 50 gallon capacity, and 76,000 BTU--more or less normal gas volume and flue size (unlike a true tankless water heater with ~200,000 BTU of heating).



> Today’s homes demand more hot water than ever before, and the 90% efficient Vertex power-vent gas water heater offers unprecedented levels of performance to meet the need. The 50-gallon Vertex delivers hot water output that rivals a 75-gallon atmospheric gas water heater. In fact, the fully condensing Vertex design is so advanced, it can deliver “endless hot water for showers”…a continuous flow of over 3 gallons per minute.* Yet Vertex is easy to install, with height, diameter and installation requirements similar to standard power-vent units.



So, does this thing cost an Arm and a Leg, or just a Leg? Installation, problem with local codes, who stocks locally, is this a do-it-yourself project (like a normal water heater) or not???

-BB


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## UncleFester (Nov 9, 2007)

Just from intuition, it seems unlikely that a water heater could "take off like a rocket". Several conditions would have to be met in order for pressure to build up. The TP valve would have to be frozen shut, there would have to be some sort of back flow preventer between the heater and the supply(any expansion would normally cause water to flow backwards into the supply), the thermostat would have to stick so the heater ran wayyy too long and the faucets have to be able to hold back the over pressure. 
In addition, water being a fluid, doesn't compress very much so there is very little elasticity to store energy in. Scuba tanks are pressure tested using water for that very reason. 
maybe if the water were heated waayyyy above boiling but kept from doing so by the pressure, and the heater springs a leak, the pressure relief would then allow the water to boil and provide the energy release to provide thrust by forcing water out the leak..... 
Just guessing here.


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## LED_Thrift (Nov 9, 2007)

If it's not lithium it won't take off like a rocket


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## BB (Nov 9, 2007)

Here is the Vertex 90% efficient Tanked water heater installation manual (PDF Link).



UncleFester said:


> Just from intuition, it seems unlikely that a water heater could "take off like a rocket". Several conditions would have to be met in order for pressure to build up. The TP valve would have to be frozen shut, there would have to be some sort of back flow preventer between the heater and the supply(any expansion would normally cause water to flow backwards into the supply), the thermostat would have to stick so the heater ran wayyy too long and the faucets have to be able to hold back the over pressure.
> In addition, water being a fluid, doesn't compress very much so there is very little elasticity to store energy in. Scuba tanks are pressure tested using water for that very reason.
> maybe if the water were heated waayyyy above boiling but kept from doing so by the pressure, and the heater springs a leak, the pressure relief would then allow the water to boil and provide the energy release to provide thrust by forcing water out the leak.....
> Just guessing here.



Exploding boilers and hot water heaters (and those that take off), are not legends... Yes a TP valve would have to fail (or somebody puts a pipe plug in one to stop a leak), a back flow preventer or well system or cold water valve turned off, but heat still available, and gas valve sticks on--all would have to happen for the water heater to explode/take off (rare--but it does happen).

Assuming that all of this happens, and the water heats to well above 200 PSI--residential hot water tanks are rated to 150 PSI (from this link, 200PSI = 382F/194C)... And some steels begin to loose significant strength above 400-450 F (if I recall correctly).

So, assuming the bottom lets loose first (I saw a quick picture on Mythbusters--did not see full episode yet--bottom is what inverted then let loose). You have 200+PSI of hot water instantly turning into steam (15PSI ATM), forcing a ~50 gallon/400lb slug of water down, and a 100 lbs of steel tank 100-400 feet into the air (as well as the expanding water/steam creating over pressure in any enclosed space and looking like an low velocity explosion...).

-Bill


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## yuandrew (Nov 9, 2007)

On Mythbusters, both tanks they tested failed at around 350 PSI.

In their test, the thermostat and high limit switch was removed and bypassed and the T&P valve removed and capped.


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## BB (Nov 9, 2007)

yuandrew said:


> On Mythbusters, both tanks they tested failed at around 350 PSI



Saturated Steam temperature would be  222.1 




C  431.8 



F

-Bill

PS: Go to http://www.discovery.com/mythbusters and you can find a few minute clip of their exploding water heater tests.


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## BB (Nov 9, 2007)

Here are a couple of short PDF lists of 90%+ efficient hot water heaters (that appear to be tank type) from various manufacturers...

US List (eligible for tax credits?)

Canadian List

Have to go through the lists in detail... One I checked was still 190,000 BTU--I was looking for a smaller one because I don't need that high of heating capacity (and re-plumbing of gas lines and possible expanded venting for the higher BTU rating)...

-Bill

PS: Although 95+% efficient and 1% heat loss for a 50 gallon water heater does sound good...


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## UncleFester (Nov 9, 2007)

I stand corrected


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## Illum (Nov 9, 2007)

Aaron1100us said:


> Just get a tankless water heater. No tank to explode. Our water heater is old and I'm thinking about replacing with a tankless one. Not for that reason but because they are supposed to be more efficient. They do take a little bit longer to get hot water and are pretty expensive. Still investigating them.




I wonder if these tankless models can be installed in the outdoors....running a propane line in would probably going to require drilling alot of holes


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## Valpo Hawkeye (Nov 9, 2007)

Illum_the_nation said:


> I wonder if these tankless models can be installed in the outdoors....running a propane line in would probably going to require drilling alot of holes



Yes, the do make outdoor tankless water heaters. See www.palomatankless.com or www.hotwater.com


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## Ras_Thavas (Nov 11, 2007)

A while back I had a failure that was not explosive but would have caused significant damage if I was not home. The tank rusted through and a small hole opened in the top of the tank. Water shot out of the tank just like a garden hose. It hit the wall on the opposite side of the garage. I noticed it at around 03:00. I remember waking up because something did not seem right. I walked around the house in my underwear and finally opened the door to the garage. It was about 50 degrees out and all the hot water made the garage look very eerie, all steamy like a rain forest.

It made quite a mess. The wall where the stream was hitting had all the texture eroded away on a good sized spot. I would have hated to see what it would have done if left alone for a couple of days.


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## Numbers (Nov 17, 2007)

I installed a new 50gal 50,000 btu in my house today. Going on vacation starting monday next week. Should I turn it off before I go or forget about it as I have always done in the past.
Is it safe to assume that my installation is good because no leaks, water or gas now, or could something pop up in the next few days while I am gone?


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## will (Nov 17, 2007)

I have an oil fired hot water heater, I turn it off if I am away for more than a day, There is the switch right by my door. When I return, I just flip the switch back on. It takes about 10-15 minutes to heat back up.


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## Valpo Hawkeye (Nov 17, 2007)

Turn your water off at the meter (unless you have a housekeeper or irrigation) and turn the selector on the water heater's gas valve to the vacation setting. Just turn in back to its original position when you get home and in about 45 minutes you should have hot water.


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## will (Nov 17, 2007)

Valpo Hawkeye said:


> Turn your water off at the meter (unless you have a housekeeper or irrigation) and turn the selector on the water heater's gas valve to the vacation setting. Just turn in back to its original position when you get home and in about 45 minutes you should have hot water.



if you turn off the water at the meter you create a closed system. any pressure build up has nowhere to go.


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## Numbers (Nov 17, 2007)

I would like to shut the water off in the house when I am away but I am not sure it's the right thing to do because if the water heater or gas boiler were for some reason, get low on water they could not fill themselves; then if either of units thermostat called for heat and the burners were ignited I would think that's a problem? 

The boiler needs to maintain minimum heat in the house so I would leave it's thermostat on a low setting with the water feed also on. For the hot water heater could I put the thermostat on the pilot (light) setting and safely close the water supply to it?


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## Valpo Hawkeye (Nov 18, 2007)

Will, you already have a closed system if your municipality requires a check valve or backflow preventer, as most do. 

Numbers, I understand what you're saying. The only realistic problem there is your boiler. However, many installers, after purging the system, turn the supply to the boiler off anyway. That way if the system leaks it doesn't cause catastrophic damage to the house. Do you have any reason to suspect you have a pressure loss? If you're curious, turn of the supply for a couple of days, then turn it back on and see if any water is lost. 

I always turn my water off when I leave, just for peace of mind. When I return and turn it back on, the system is just as I left it. The meter barely spins when I turn the supply back on. The chances of a failure in your domestic (potable) water system are higher than a failure on your boiler side (which runs only at about 12-20 psi). If you're really concerned about freezing, they make little boxes that will call up to 3 numbers if you're house drops below a certain temp.


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## will (Nov 18, 2007)

Valpo Hawkeye said:


> Will, you already have a closed system if your municipality requires a check valve or backflow preventer, as most do.
> 
> .



You are correct - The only requirement here is a check valve on underground lawn sprinklers to prevent back flow. That is only necessary on the portion of the water supply that goes to the sprinklers, not the entire system.

Then, the failsafe is the Temp and Pressure valve on the heater.


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## Valpo Hawkeye (Nov 18, 2007)

will said:


> You are correct - The only requirement here is a check valve on underground lawn sprinklers to prevent back flow. That is only necessary on the portion of the water supply that goes to the sprinklers, not the entire system.



Wow. That's very minimal protection for the water supply. In our area, a vacuum breaker and a check are required, and a full-blown backflow preventer is needed on any fire-prevention system or certain irrigation systems. A check valve is also required for the entire water service, even domestic supply.


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## will (Nov 18, 2007)

Valpo Hawkeye said:


> Wow. That's very minimal protection for the water supply. In our area, a vacuum breaker and a check are required, and a full-blown backflow preventer is needed on any fire-prevention system or certain irrigation systems. A check valve is also required for the entire water service, even domestic supply.




My house was built in 1927 - there may be a requirement on new construction, but I don't know that. There could even be something on the water meter ( mine is located at the curb, underground )


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## Numbers (Nov 18, 2007)

As you can tell I am in NY too and the only back flow device is on my irrigation system, nothing on the water coming into the house. Mine was built in 1960 with extensive renovation/construction in 1990 at which time everything was up to code. For the boiler I will do as I always do and just turn the thermostat down (I dont believe I have any pressure loss, but now that you pointed it out I will test when I get home). For the hot water heater, since it is brand new, I will turn off the gas and water supply to it for the few days I am away. 
It is running fine. I assume I saved enough money to buy a new light by installing it myself.
Anyone know what they get to install a water heater?


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## Valpo Hawkeye (Nov 18, 2007)

Numbers said:


> Anyone know what they get to install a water heater?



Depends on your market and the company, but anywhere from $200-$450. The company I work for charges about $300.


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## bfg9000 (Nov 19, 2007)

Ras_Thavas said:


> The tank rusted through


There are now completely rustproof electric water heaters. 

And as was pointed out last time, feeding a small electric heater with preheated water from a gas tankless model (one with a pilot light) will ensure continued hot water even if electric _or_ gas service is interrupted (or if one of the heaters fails). The small, highly insulated tank heater serves as a buffer for the variable temperature output of the tankless heater, and the bulk of the heating is done by the more economical gas heater in this hybrid setup.


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## Numbers (Nov 19, 2007)

Wow, 
I am a happy camper. Now I can never run out of hot water, I saved a few hunderd $ on installation and on top of that I checked my CC bill on line and they charged no sales tax on the purchase of the unit itself.


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## James S (Nov 19, 2007)

They are updating those laws here. If you have a well pump anyway that is connected to the regular house plumbing. This is going to affect me at some point. They are going to require that you have a low pressure zone or something like that between your pump and the plumbing. I'll probably just install and automate some valves so that I can switch back and forth that way rather than relying on water pressure differences which always seemed sketchy to me as those things all fluctuate quite a bit normally.


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## Valpo Hawkeye (Nov 19, 2007)

James S said:


> They are updating those laws here. If you have a well pump anyway that is connected to the regular house plumbing. This is going to affect me at some point. They are going to require that you have a low pressure zone or something like that between your pump and the plumbing. I'll probably just install and automate some valves so that I can switch back and forth that way rather than relying on water pressure differences which always seemed sketchy to me as those things all fluctuate quite a bit normally.



I'm not sure about the code in your area, so don't take this as gospel but... 

There's no way that would fly in Indiana or any state under the UPC (Universal Plumbing Code). If they're requiring that the two systems be seperated, you cannot do it by anything other than a certified backflow preventer. When the pressure on the domestic side exceeds the pressure on the service (main) side, instead of a backflow situation occuring, the water is released through a drain. An automated system such as you describe is too open to failure, i.e. both solenoids open at the same time. Just as an FYI.


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