Shutoff Valve in Hot Water Line of Water Heater

SewerRatz said:
Here is the trouble. If water that is in a pressure vessel, boiling point is a whole lot higher than normal. The more pressure on the system the higher the boiling point is. They call this water super heated. When this super heated water is exposed to normal atmosphere it flashes to steam. Which can and in the case I pointed out did melt the rubbers on the faucets, and the Sloan flush valves.
Click to expand...

You're right about the rise in boiling point - I completely overlooked that.

Still though there are 3 safety mechanisms that have to fail

- high temp cutoff not working
- thermostat not working
- TPV not working

So all these failed in your example apparently. I can see the point of not having a shutoff on the output of the WH, but if all three safety mechanisms fail I would say that this would be a big problem in MOST installations regardless.
 
Ahh found my Chicago code book. Dang brother-inlaw had it.

From the 07 Chicago plumbing code:
18-29-503.1.1 Shut-off valves Shutoff valves for water heaters or heated water storage tanks may be installed on the inlet side only.
 
I am an example of someone who shut off the hot water valve and the main

Ian Gills, "Robin Hood", thank God you posted on here in rebuttal and got the debate going and then cleared up....thanks to SewerRatz expertise and further input.

I noticed water on my garage floor and traced it back to a drip leak at a section right near the hot water shut off valve. My husband and I were leaving for a cruise that early morning and had no time to call the plumber. Touching the drip it was hot water, and I concluded it would stop if I shut off the hot water valve, which it did. I then went outside and turned off the main and we left for a 10 day cruise. I had no idea this was a potential killer bomb. Now I know. Hope others will chance upon this thread and learn the danger involved in the simple act of shutting off a shut off valve. Wow, I get sicked thinking about what I could have caused. The gas company should really send out stickers to be placed next to any water heater hot water shut-off valve to each and every home, that says "do not shut off this hot water shut-off valve for more than 30 minutes - explosion danger!!".

Thank you Ian Gillis, "Robin Hood", and SewerRatz!!!!!!!! Your posts may save lives.
 
Like I have been saying for years, you need REDUNDENCY- back up to the single stupid relief valve.

And guess what boys, its made, and no one uses it because granpa didnt have one.

http://media.wattswater.com/es-BRV.pdf

http://www.watts.com/pages/_products_details.asp?pid=564

Anyone ever heard of a tee with a secondary, plain pressure relief valve on the heater also? Is 12 bucks too much to save a house or heater? Got a car without an emergency brake lately?

It was too expensive for for the Japanese at their sieve of a nuclear plant, and now have a look at what their lack of forethought caused. -30 kilometer circle of new wilderness, and fish that glow in the dark.

Funny how they floated their department stores on huge springs. Built the reactors rock solid. I guess the Prada purses are more important that a few hundred thousand houses being abandoned.
 
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ballvalve said:
Got a car without an emergency brake lately?
Click to expand...

Actually, the new car I just bought uses a computer driven hydraulic system for the parking brake...there is no direct mechanical lever or pedal to mechanically operate the brakes. If the engine is running, it works on all 4 wheels, if it's not, it only works on the rear wheels. You pull the little switch up to activate, and push it down to turn it off.

As we've gone over multiple times, the code approved method is an expansion tank along with the factory T&P valve. If doing more makes you feel better, go for it, but millions of people don't do more and their tanks haven't blown up, nor do I expect that they will.
 
Wheel chocks are required by law in many places for trucks because they are mechanisms in PLAIN SIGHT that do not fail.

And all my tractors and excavators have hydraulic acculumulators, seem to NEVER break or leak, and within a few seconds lock up all drive mechanisms when the engine is killed. As soon as you turn off a 100,000 pound excavator, you have nothing to do but go home, no levers to pull. Great system.

Very handy on the edge of a cliff when the engine dies and braking power ends. Might not work so well on a pickup at 80 MPH on the freeway.

A hydraulic accumulator on autos, with brains, would be a huge safety factor for braking and parking.

Funny how a backup relief valve disturbs everyone. But all those stupid backflow valves that we lived without for 150 years are gods new standard without question. How many of you got sick from reverse flow water? Better to regulate chickens in the market for bacteria.
 
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ballvalve said:
Funny how a backup relief valve disturbs everyone. But all those stupid backflow valves that we lived without for 150 years are gods new standard without question.
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Because you propose it instead of a thermal expansion tank which is about the equivalent of us saying strip the brakes off your truck because they might fail and use "Fail Safe Wheel Chocks" instead....

The fact is your relief valves can and do fail quite often and plumbed to a drain and in a failed or, operational state could conceivably run full flow unnoticed until a well goes dry or, you have a heart attack when you open your water bill.

So jump off your engineer soap box and realize the data and logic you are applying to your brilliant solution is flawed badly.

That is why we repeat ourselves every time you mention this....

We will repeat it as often as you do, because bad advice does need to be exposed as such.
 
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Sure expansion tanks help, when NEEDED, but they have the same pressure rating as the heater body, so blowing the internal bag is not back up like another pressure valve. You can do another myth busters video with a expansion tank in the circuit, and the simple question is which one blows first.

Unless you have 2 shut off valves on the water heater and a absent relief valve, the value of the exploding water heater videos is the same as a video showing what happens when you build your charcoal barbeque fire right under the gas tank of your motor home.
 
Okay... Let me get this straight now...

If someone turns off the two valves on the inlet and outlet of the water heater... (Even though us plumbers don't put one on the outlet)

and...

If the T&P Valve fails..... which is easily tested and should be regularly.....

and...

If the Thermostat fails in a manner which causes heating continuously 50-50 chance....

and....

If the TCO (Thermal Cut Off) fails....

Oh Boy Mr Engineer... Just how much redundancy do you want anyway?

By your theory we've got your dump truck parked:

The emergency brake is set...

and

The engine is off and in lowest gear...

and

the wheel chocks are in place

and

the truck is on level ground....

All we can do now is take your silly azz little ball valve and throw it at the window breaking it....

Come on Ball valve grow some grey matter will ya?
 
Everyone must be bored around here.

My point was that the exploding water heater videos are fun, but almost irrelevant. As you well point out with all the other devices to be bypassed.

Leave out the hot shut off, and now you have lots of pipes and hoses that can become your pressure relief valve.

As to grey matter, dump trucks do not have nitrogen filled liquid hydraulic accumulators for the e-brake. And the dump truck driver with the most of it actually uses his wheel chocks.

In case you missed the POINT - expansion tanks provide no help with a run-away [tampered with] water heater.
 
ballvalve said:
Everyone must be bored around here.
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No, We are just tired of you the "Unknowing" spewing your lack of wisdom on this subject and determined to rebut the bad advice you consistently spew...

We have tried to educate you on the subject but due to a lack of absorbency your grey matter repels knowledge...

This is a common occurrence in some people in your chosen field. Most continue to educate themselves all through life and become very good in the field. Others blindly decide at some point that they know everything and at that point cease to have any value.

ballvalve said:
In case you missed the POINT - expansion tanks provide no help with a run-away [tampered with] water heater.
Click to expand...

And your ball valve with a relief does?

If you will note at the product link you provided it states...

"It is for applications that require a means to shut off the water supply to the water heater and for providing protection from excess water pressure caused by thermal expansion."

Your assumption that it provides protection with a runaway water heater is completely out to lunch.

A properly sized T&P Valve will provide that protection. In looking at the specifications for the Watts 100XL T&P Valve you will not the following lines of information that do not appear on the product you recommend...

A.S.M.E Rated*, CSA Listed. Self-closing T&P Relief Valves
for Water Heaters up to 105,000 BTU/Hr.
The combined 2 in 1 T&P relief valve provides the least expensive and proven means for protection against both excessive
temperature and pressure emergency conditions.
Provides fully automatic temperature and pressure relief protection for hot water storage tanks and heaters up to 105,000 BTU/HR.

Each water heater and hot water storage tank shall be
equipped with a CSA and A.S.M.E. Rated* automatic temperature and pressure relief valve to protect the heater from excessive pressure and temperature. The device shall be ANSI Z21.22 certified. The BTU discharge capacity of the device
shall be in excess of the BTU input rating of the heater.

Now I'm not a General Engineering Contractor so I don't profess too have knowledge about digging irrigation ditches, land leveling, installing driveways, and ditch digging... Frankly I don't want that knowledge... I'll bow to your excellence or, hire some undocumented day laborers to do the work...

I'm a plumber! That is my area of expertise...
The engineers at Watts are a slightly different type of engineer than you are...
They have expertise in the safety controls needed on a water heater. So me the plumber having an awareness that you lack have decided that...

I will have a safety device that is CSA and A.S.M.E. Rated, ANSI Z21.22 certified, With a BTU discharge capacity in excess of the BTU input rating of the heater...

Now go dig a ditch or, something....
 
The unknowing with repellant soft grey matter dont know the meaning of redundency and rely on granpas valves rather than the new choices in conjunction with the valve that comes installed on the heater.

Must be bored not having Ian to kick around lately. Glad to be of service.
 
Wow, there's a lot to unpack about the car dealership "horror story". There's no mention of the age or how many decades past the Warranty period the water heater was. There is also no mention of how many (at least yearly) inspections had been skipped by the business owner. Inspections that are usually required for privately owned buildings open to the general public. The scenario you described would require the TCO, the thermostat, and the T&P valve to fail simultaneously (winning the lotto and being struck by lightning on Feb. 29th) because only one operational safety would be required to avoid that. If I remember all the details in the posts, I believe it was stated that it was a 120 gallon heater which would have been way overkill for a few restrooms (no bathing facilities) and undersized if they were using it to wash cars. The more likely scenario is either someone tampered with the heater to bypass the thermostat or the safeties (TCO or T&P valve) or ignored the regular fault opening of the T&P valve. If, as stated in the post, all the gaskets in the faucets and toilets melted you would not have steam coming from them, you would have warm water at best because failed gaskets cause valves to leak. If all the valves were leaking you would have a constant flow of cold water into the water heater. And now onto the whole exploding water heater myth. The tanks on water heaters are only designed to hold slightly more pressure than the T&P rating. Anything more would cut into the manufacturer's profits. They are also designed to not fail catastrophically (explode). Seams (welds) will zipper open and instantly reduce pressure to around the incoming water pressure.

The other item I would like to address is everywhere you look people are saying "test your T&P valve regularly" (anywhere from annually to monthly). Let's get this straight, you are not "testing" your T&P valve, you are manually forcing it open and dumping hot water on your floor (because most T&P valves are not plumbed to a drain). To test a T&P valve for functionality you would have to exceed it's temperature and/or pressure ratings. As well, manually opening the T&P valve often can actually lead to premature failure (and potential for scald injuries). Because of the increased temperature in the water heater, there is a high level solubilized minerals in the water in the tank. When you manually open the T&P you can cause either mineral buildup on the seal and/or seat (fail open) or mineral buildup on the stem and/or spring (fail closed). Stop opening your T&P. If you are worried about the integrity of the T&P, just replace it.

Now, onto the actual subject of this thread. Shut-offs on water heater outlets. It amazes me when people talk about what is in the code book like Moses just brought it down from the burning bush, but doubt it's validity when something isn't in the code book that they feel should be. Plumbing code in most states is governed by the department of health. 95% of the code is about health and safety (like having a T&P valve on a water heater), the rest is comfort and convenience (like flow rates to fixtures). If there were a real (not a perceived) health or safety concern with shot-offs on water heater outlets, it would be explicitly prohibited by code. Plain and simple. Besides, what would you call zone valves, other than shut-offs on a water heater (or boiler) outlet.

Without the shut-of on the outlet you would be forced turn off the main and drain down the entire building to change out the heater, replace side mount anodes, replace the elements on electric water heaters or control valves on gas water heaters. Why might you ask. It's because most homes do not have sinks with separate valves anymore. They are single handled combination valves. When you turn off the supply to the water heater, you still have cold water feeding those combination valves. You can't drain down the water heater, because the reduced pressure on the hot side of the valve allows cold water to flow across the valve and into the hot water lines and back into the water heater. Draining down the entire building is also extremely time consuming because the water heater drain valve is usually the lowest point in the plumbing system and they are woefully undersized (1/4 to 3/8 inch at best).

OK, let the hating begin.
 
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Ian Gills said:
Are all of you completely mad? Or is it 1 April?

Even a DIYer knows this one, which says something.

It is incredibly dangerous and absolutely against code to have a shut-off on both the inlet and outlet of a hot water heater. If both are closed, the WH relies completely on the proper functioning of the PRV to deal with pressure/expansion changes and faults if the heater is left on.

If the PRV fails, then we start to see explosions of the type some of you post links to on this site every now and again.

My neighbor has valves on both the inlet and outlet of his WH and I live in fear. Say he shuts them both off and forgets and the PRV fails?

Shut-offs on WHs should only be installed on the cold side. That way, the fixtures and fittings (think washer hoses) of the hot supply will also take the strain of any increase in pressure should the PRV fail and there is fault with the WH. There is therefore less chance of a boom.

How many bombs are you guys making?

LONG LIVE D.I.Y.
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Please explain to me how a heater will explode by pressurizing with water vrs all the house valves close. Relief opens at 150 lbs or 210°. Don't heater blow up by running dry still firing then water enters the vessel flash into steam that expands 1600 times
 
Lot's of discussion here about the potential for explosion.
That's certainly an important thing to consider, as I will below.

But.. I don't see anyone mentioning MY current situation.

My hot water heater's tank failed last night. It is leaking on my floor.
Of course the original installer did NOT install a pan. (Kind of hard to do after-the-fact once it's attached via solid pipes, can't lift it)

Now we are waiting for a home warranty company to get this replaced.
Meanwhile I have turned off the cold water intake to the heater, unplugged the electricity and turned off the gas. This thing is NOT going to explode.

Of course I don't have a valve on the hot water side.

So?!?!?
So ever time someone in the house forgets, turns on both the hot and cold at a faucet or the mixing valve of a shower the COLD WATER BACK-FEEDS INTO THE HOT WATER LINES, DOWN TO THE BROKEN WATER HEATER AND RE-FLOODS MY GD FLOOR!

So.. I certainly don't want to explode my house.
Nor do I want to violate a code and so invalidate my insurance.

But seriously! WTF would anyone go down there, turn off both valves, leave the electricity plugged in and the gas turned on, walk away and leave it like that?!?! And if they did what are the odds that the thermostat and pressure relief valve would both fail??

Is there something I am ignorant of here?
Or is the conventional wisdom more based around dealing with 1920s silent film villain murder methods and less around the practicalities of sharing a house with a family and not wanting flood damage?
 
Steam from water expands 1600 times. Their is no relief valve that can handle that rate. It doesn't matter if there is a valve on the outer but for service it's not necessary. Why take a chance closing off both valves with the burner on. Water or boiler doesn't matter IT'S A BOMB look on you tube. 40+ years running commercial and industrial service only was scared one time. Not from explosion from a over fired boiler the wood sub structure. Heaters explode when the burner is on boiler runs out of water wh or boiler is red hot and water is added flashes to steam and explodes. Oh your probably DEAD! Walked away from one job at a chemical plant wanted me to work on a running chiller that need to be shut down and they said no bye. Called back 30 hours later after another service person got electrocuted.
 
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Bobberman said:
Is there something I am ignorant of here?
Or is the conventional wisdom more based around dealing with 1920s silent film villain murder methods and less around the practicalities of sharing a house with a family and not wanting flood damage?
Click to expand...

Turn off all of the hot stop valves supplying your sinks and tub.
For extra caution, consider hooking a garden hose to the WH drain valve, run the other end of the hose to a floor drain or sump. Open the drain valve.

If you don't have stop valves, you could turn off the water into the house overnight; that would limit leakage in the case you describe.
 
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