Over 698,000 strictly plumbing related posts
Plumbing education, information, advice, help and suggestions are provided by some of the most experienced plumbers who wish to "give back" to society. Since 1996 we have been the best online (strictly) PLUMBING advice site. If you have questions about plumbing, toilets, sinks, faucets, drains, sewers, water filters, venting, water heating, showers, pumps, and other strictly PLUMBING related issues then you've come to the right place. Please refrain from asking or discussing legal questions, or pricing, or where to purchase products, or any business issues, or for contractor referrals, or any other questions or issues not specifically related to plumbing. Keep all posts positive and absolutely no advertising. Our site is completely free, without ads or pop-ups and we don't tract you. We absolutely do not sell your personal information. We are made possible by:
Author:
Thomas (MS)
Hello, I have a Pro-line FlameGuard 50 gallon gas water heater made by the American Water Heater company. The water heater was installed when the house was built 8 years ago. If the thermostat and the temperature/pressure relief valve both fail, will the water heater explode?
|
Post Reply
|
Author:
KCRoto (MO)
If you had a closed system, and the T+P valve was stuck shut, and the gas valve was stuck running wide open, then the possibility exists. Usually T+P valves don't get stuck closed unless they are very old. It is far more common that they discharge and keep leaking from calcium buildup holding them open/ stuck between the sealing surfaces. I personally have never seen a gas valve on a hot water tank stuck open, but someone else here may have. I have seen valves that fail to operate properly, but they kept shutting down entirely; they weren't getting current from the thermocouple for some reason.
Edited 1 times.
|
Post Reply
|
Author:
bernabeu (SC)
If you have a closed system:
YES - 80% chance
This is why the TPRV should be tested annually.
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
|
Post Reply
|
Author:
Thomas (MS)
Not sure what a closed system is. Is that a system that won't back feed into the city water supply? How can I tell if I have a closed system?
|
Post Reply
|
Author:
hj (AZ)
I had a 75 gallon heater with a failed thermostat and the burner was running wild. The T&P valve discharge was also "clogged" somewhere in the wall. Fortunately, the installer had made a bad solder joint on the discharge line so she called me to fix the leak, not knowing that it was just the tip of the iceberg.
|
Post Reply
|
Author:
hj (AZ)
Actually ANY heater is a danger if the water exceeds 212 degrees, which can happen because while it is NOT a closed system, it is still under pressure. At 80 psi, not unusual for a house, it can reach 325 degrees, which will make a very nice explosion if anything were to rupture.
|
Post Reply
|
Author:
m & m (MD)
All water heaters are shipped with an I & O manual. In the maintenance section of the manual, the homeowner is instructed to manually test/operate the T & P valve at least once a year. The T & P is the last line of defense against a runaway fire.
|
Post Reply
|
Author:
bernabeu (SC)
'fire' as in gas valve or electric element
see: [www.mass.gov]
Effects of a 5 gallon hot water heater explosion - Avon High School 5/11/00
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
Edited 2 times.
|
Post Reply
|
Author:
hj (AZ)
Going pedantic on us? "Fire" as in "flame". An electric element heats, it does not "fire".
|
Post Reply
|
Author:
Thomas (MS)
What's a "closed system"? Is that a system that's designed not to backflow into the city water supply? How can I tell if I have a closed system?
|
Post Reply
|
Author:
bernabeu (SC)
makes little difference
merely 'less' risk if open system - but danger is still present
if liquid water gets over 212 while pressurized
then tank ruptures resulting in pressure = 0
liquid will 'flash' into steam
volume of steam = 1,700 times that of liquid water = KABOOM
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
|
Post Reply
|
Author:
hj (AZ)
You look at it, but you have to know what to look for. But in this context, even the normal city pressure can create a potential hazard. Excessive pressure CAN compound the problem but ANY pressure would be dangerous under the proper circumstances.
|
Post Reply
|
Author:
bernabeu (SC)
'fire' as in 'fire up the heater'
? pedantic ? perhaps
The 'cold war' was caused by a de-coder NOT being pedantic!
General G. Patton to headquarters: 'Sighted bridge over Danube and it's blue'
decoded as: 'Sighted bridge over Danube and it'd blown'
Headquarters to Patton: 'Hold and consolidate position'
That is why the Soviets got to Berlin first. Gospel truth!
? pedantic ? you betcha
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
|
Post Reply
|
Author:
hj (AZ)
You have to know the contect that "fire" is being used it.
Is there fire in the heater?
Is the heater fired up?
Take this gun and fire at the heater.
|
Post Reply
|
Author:
Thomas (MS)
My water heater sits in a square steel pan with 6" walls. There's a pvc drain pipe connected to the pan that's routed to the outside of the house. The T&P valve is mounted on the side of the heater near the top. There's a copper drain pipe connected to the T&P valve that extends down to about 4-5 inches above the steel pan.
I tested the T&P valve by pulling up on the lever. Hot water shot out of the copper drain pipe into the steel pan then stopped when I pushed the lever back down. From what I can gather that's a good test.
Is there anything else I can do to insure that my water heater is in good shape?
|
Post Reply
|
Author:
bernabeu (SC)
yes, that is the proper test
it shows that the mechanism is not 'stuck'
it shows that the discharge piping is 'clear'
we all trust the actual TPRV mechanism to function
the only other 'practical' maintenance is to drain a gallon of water from the bottom periodically as per the manual which should be with the heater
if no manual, get one from the manufacturer (probably for free)
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
Edited 1 times.
|
Post Reply
|
Author:
bernabeu (SC)
hj,
also: 'fire the bum'
ps.
Quote
You have to know the contect that "fire" is being used it.
perhaps you meant: context
gotcha
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
Edited 1 times.
|
Post Reply
|
Author:
Thomas (MS)
Many thanks.
I'm thinking about getting a tankless water heater when the time comes. Are tankless water heaters less prone to overheated water explosions? That picture of the Avon School looks pretty scary.
|
Post Reply
|
Author:
hj (AZ)
quote; 'fire the bum' [
I medieval times they used real "fire".
|
Post Reply
|
Author:
WC (VA)
Reference earlier post.
For clarification - Sorry, not actually plumbing related.
"Sighted bridge over Danube and it's blue" -- If this was the intended transmission even that would be a joke. The BRIDGE itself 'may' have been blue, but The Danube river is not blue - at least not at any of its part in Germany. Seen it - crossed it - and it is dinghy brown looking. (IE - I doubt the Red Sea is red.)
The US did not choose to enter Berlin first. Why would we want to sacrifice any soldiers at that point in time of the war? Victory was already established. The US Army did allow me to enter Berlin -- 18 years later - with no problem whatsoever.
|
Post Reply
|
Author:
bernabeu (SC)
....as in 'the blue danube'
Patton was, in fact, somewhat of a 'loon'
the story is true
check out "Johnny Come Lately", a British novel which was NOT derogatory, as 'come lately' was merely a common British expression meaning later or late
history from an ally's point of view
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
|
Post Reply
|
Author:
packy (MA)
my wife just asked me if i "extinguished" the cat. yes, i replied. but she (the cat) wants to come back in now..
|
Post Reply
|
Author:
Plumber3 (FL)
In a "closed system" you could double your safety chances by installing a "Pressure Relief" on the cold side of you system. Pressure reliefs are now required by code in Florida, we install a tee off of the exterior hose bib water line and install them there and the hose bib on the other side. BUT if you live in cold weather conditions with "Frost Free" hose bibs then you could install it somewhere indoors where if it went off you could let water flow. They are usually adjustable between 50-175psi
|
Post Reply
|
Author:
Thomas (MS)
Sounds like a good idea. So what you're saying is that a T&P relief valve could be installed anywhere on the cold water line and if the water heater thermostat and water heater T&P relief valve both failed, the T&P relief valve on the cold water line would open and prevent the water heater from exploding, right?
|
Post Reply
|
Author:
hj (AZ)
It is a "P" valve, not T&P. If it is not ON the water heater it does not need a temperature component.
|
Post Reply
|
Author:
Thomas (MS)
Thanks hj. What's your take on having a pressure relief valve installed on the cold water line?
|
Post Reply
|
Author:
bernabeu (SC)
You had best not.
Should you have a 'run away' heat condition and said valve were to pop open relieving pressure the 'superheated' water could still flash into steam.
The TEMPERATURE relief is the important element.
If you are really 'paranoid' install a second TPRV on the heater.
If no tapping available:
Install a 'street tee' on the HW discharge (male into tank)
(available from our sponsor)
TPRV into 'run' (temperature element will be inserted enough as a 'back-up')
HW out from side (bull of tee)
Belt AND suspenders!
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
Edited 1 times.
|
Post Reply
|
Author:
Thomas (MS)
Thanks for the info bernabeu.
I mainly want to do anything I can to prevent a catastrophic explosion.
Are tankless water heaters less prone to overheated water explosions?
|
Post Reply
|
Author:
hj (AZ)
BAsically useless, but no problem with it, because the T&P valve will limit the pressure to 150 psi.
|
Post Reply
|
Author:
hj (AZ)
When they are working correctly, yes, but we are talking about an abberation, and there is no way to tell how they would work under those conditions. Their saving grace is that they only have a small amount of water to "overheat", and the volume of superheated water is the dangerous thing.
Edited 1 times.
|
Post Reply
|
Author:
Thomas (MS)
Thanks again hj. Your encyclopedic knowledge of plumbing systems is much appreciated.
|
Post Reply
|
Author:
myles29 (VA)
If there is a clog in the pressure and temperature relief valve, and excess gas is trapped, yes, there is a possibility of explosion. But you don't have to worry since water heater explosions rarely happen, and there are things you can do to prevent this. You can have it regularly checked and make sure to maintain the recommended water heater temperature.
Edited 1 times.
|
Post Reply
|
Author:
harry02 (VA)
Hi, OP! A leak in your pressure relief valve might cause an explosion. Leaks in the valve mean that there is too much pressure inside the tank and the valve cannot effectively handle it. This means that it can fail anytime and might even result in an explosion. You can find more information on the causes of water heater explosion in this article: [#$%&].
|
Post Reply
|
Please note:
- Inappropriate messages or blatant advertising will be deleted. We cannot be held responsible for bad or inadequate advice.
- Plbg.com has no control over external content that may be linked to from messages posted here. Please follow external links with caution.
- Plbg.com is strictly for the exchange of plumbing related advice and NOT to ask about pricing/costs, nor where to find a product (try Google), nor how to operate or promote a business, nor for ethics (law) and the like questions.
- Plbg.com is also not a place to ask radiant heating (try HeatingHelp.com), electrical or even general construction type questions. We are exclusively for plumbing questions.
Search for plumbing parts on our sponsor's site:
Special thanks to our sponsor:
|