Shutoff Valve in Hot Water Line of Water Heater

[BurleyMike]

Come on now, you don't have to worry about excess pressure if you have brass Zurn pex fittings!

 

[Basement_Lurker]

Many thanks for the clarification.

I must have been confused on this one.

I guess I am just be one of those weirdos who likes to see installations done as per the manufacturer's installation instructions, which never show a hot-side shut off valve for a traditional single tank installation.

You are correct to follow the manufacturer's installation guides, however, just like the installation requirements in a code book, they are just minimum guidelines on how to do it. While I don't agree with you that having a shutoff valve on the hot water line is a safety issue, I will say that for a normal sized home, having a hot water shutoff isn't really necessary since it doesn't take much longer to drain down the hot water lines while you are draining down the tank.

However, I will say that I always install a valve on the outlet and inlet side of the tank. But that is just because of the way I plumb in a tank with flex hoses; it just makes it so much quicker and simpler for the next guy who replaces the tank.

 

[Sponsor]

 

[hj]

valve

There is no prohibition against a valve on the hot water side, in fact mechanical engineers usually specify one on the larger projects. In a parallel multiple heater setup they would be required in order to isolate individual tanks when they fail. In other situations they can be a convenience. But in systems with basic flaws, they will mask the problem.

 

[SewerRatz]

I swore it was in the Illinois plumbing code, but I do know many local codes which can be stricter than the Illinois code does not allow a shut off on the hot discharge side of the heater.

As for there is no difference than having a shut off valve on the hot side or a faucet making it a closed system, there is a HUGE difference. I was called by a car dealer that told me they had smoke coming out of their water closets. When I got their it was steam coming out of the W/C sinks and wall hydrants for the car wash. I walked up to their water heater it was running non-stop, the hydro-stat failed, and the P&T valve was frozen shut. I shut the heater down opened a yard hydrant till cold water ran. Replaced the hydra-stat and P&T valve, as well as rebuild all the Sloan valves, faucets and any other valve that used a rubber to make a seal. If for some reason they had a ball valve on the outlet and it was closed that tank (120) would of launched it self and taking out half the dealership. But they got lucky the water was so hot it back flowed through the cold water and meted the rubber seals.

So I say NEVER NEVER NEVER put a shut off valve on the hot side of a tank. So damn what you need to drain down the hot side. Big whoop.

 

[theplumber]

If your local codes allow it, I'd put one on both sides just so you don't have to drain it down. The real benefit of having the shut off on the supply side is mostly for that 8pm bottom of the water heater blows out on you moment. That way you can flush the toilet as much as you like until you get the new heater in. Also if you don't ahve one on the supply side and you just have a gate valve for your main, it will not shut off the water completely. Depending on where the WH is, it could mean the difference of a ruined wood floor or just a wet smitty pan that causes no problem.

 

[Jar546]

I believe Chicago does prohibit the valve on the hot side.

 

[Verdeboy]

I swore it was in the Illinois plumbing code, but I do know many local codes which can be stricter than the Illinois code does not allow a shut off on the hot discharge side of the heater.

As for there is no difference than having a shut off valve on the hot side or a faucet making it a closed system, there is a HUGE difference. I was called by a car dealer that told me they had smoke coming out of their water closets. When I got their it was steam coming out of the W/C sinks and wall hydrants for the car wash. I walked up to their water heater it was running non-stop, the hydro-stat failed, and the P&T valve was frozen shut. I shut the heater down opened a yard hydrant till cold water ran. Replaced the hydra-stat and P&T valve, as well as rebuild all the Sloan valves, faucets and any other valve that used a rubber to make a seal. If for some reason they had a ball valve on the outlet and it was closed that tank (120) would of launched it self and taking out half the dealership. But they got lucky the water was so hot it back flowed through the cold water and meted the rubber seals.

So I say NEVER NEVER NEVER put a shut off valve on the hot side of a tank. So damn what you need to drain down the hot side. Big whoop.

That tank was already a bomb. You just arrived in time to deactivate it. If someone was stupid enough to close the valves, it may have blown up before you got there, but as someone said, "you can't fix stupid." A better idea would be to create and enforce a preventive maintenance schedule to test the T&P valve, etc..

 

[SewerRatz]

I believe Chicago does prohibit the valve on the hot side.

I think so too, but its to dang cold out for me to run out to my truck and dig up the Chicago code book. I wish they post the Chicago code online, would make life so simple, but then they can not charge you $125 bucks every other year to get the new code book.

Verdeboy: Well if they turned off the cold valve, the presure would of melted the rubbers in the hot side of the faucets.. actuly it did, as I think a bit more what I had to do to repair the stuff. But in this case the P&T Valve was only a year old, and the thermostat died in the on postion.

I had a lady e-mail these pics and told me she heard a loud bang and a pop come from her water heater. I told her to get out of the house now and call the gas company to turn off the gas to the home. I showed up an hour later as the gas company guy was just leaving.

 

[Frenchie]

Never mind that, he's not even making sense.

He says what saved it was that the hot water backflowed on the cold side. Steam coming out of the toilets...

How would a valve on the hot side have prevented that, or affected the situation in any way whatsoever?

 

[SewerRatz]

Never mind that, he's not even making sense.

He says what saved it was that the hot water backflowed on the cold side. Steam coming out of the toilets...

How would a valve on the hot side have prevented that, or affected the situation in any way whatsoever?

Well in this case the cold water got used more than the hot, with the increased pressure in the tank it backflowed towards the water closets and the other faucets that where used. Now I also posted that I did have to replace rubber washers that melted away in some faucets as well. If some one turned off the cold water supply the water still would of melted the rubber seals in the hot taps. Now if there was a shut off valve (which are normally ball or gate vales) on the hot side as well as the cold site and they both where off, this tank would of blown up. I am sorry I did not mention that I did have to replace washers on the hot taps as well. The fact of seeing steam out of a water closet was pretty amazing and the detail of replacing rubber seals on both hot and cold fixtures slipped my mind.

 

[Probedude]

As for there is no difference than having a shut off valve on the hot side or a faucet making it a closed system, there is a HUGE difference.

Worked out great for that particular instance, but I'm sure we could all draw on paper a situation where it wouldn't have helped.

If some one turned off the cold water supply the water still would of melted the rubber seals in the hot taps.

Only if there were flow. With no flow, the heat would have been dissipated long before reaching those close faucets so they would never see the scalding temp.
Though I doubt they could melt anyways at boiling water temps since that's as high as it would have been.

 

[Dunbar Plumbing]

Is there any model code, manufacturer's installation instruction, or just plain reason that prohibits the installation of a shutoff valve in the hot water line coming out of the top of a water heater?

One of the most dangerous situations you create.


Two valves off, water heater kicks on and the T&P is clogged...


A pressure cooker that when it explodes, will kill and destroy your property.

Having the ENTIRE plumbing system to use as a buildup for when a supply line blows or forces a fill valve to malfunction, anything is better than containing that water heater expecting that $7 relief valve to open up when you need it most.


I've removed every hot side shutoff on every water heater I've replaced, no exceptions and I've warned every customer of the ones I've beared witness to.

Things can and will go wrong in plumbing and just because you know how your plumbing system operates, doesn't mean your wife, kids or the incoming new property owners know what kind of bomb you built in the basement.

 

[Frenchie]

Ratz, what you're basically saying , then, is:

if there was a shutoff on the hot side, and if they shut it off, and also closed the (existing) supply-side shutoff...that would be really be dangerous... if or when something went wrong with the t&p valve.


Whereas if there isn't a shutoff on the hot side, they could only shut off the cold, and so if or when something goes wrong with the t&p, at least the seals on the faucets (hot or cold) can blow & let off some of the excess pressure?


I have to ask you why the hell anyone would turn off the inlet OR the outlet to a tank? What possible scenario you can see where someone would do that, unless they were swapping it out?

 

[Dunbar Plumbing]

I have to ask you why the hell anyone would turn off the inlet OR the outlet to a tank? What possible scenario you can see where someone would do that, unless they were swapping it out?

Because people are effing retarded most times when they have a leak in their home, and they start that chain reaction of shutting valves off until the leaks stop, not understanding that there's a water heater sitting there operating because they think the device shuts down when the water is turned off.


That's simply not true.

Ian Gills is spot on with his thinking and this is where any mode of thinking that implies you got any sense about you does NOT need to be a reference back to any code, provision, statute or law.

It's called "logical thinking" and you either have it or don't.


Code in KY doesn't restrict that hot side valve, but that doesn't mean that I as a plumber don't understand that two valves off and a thermostat kicking on to either satisfy a temp drop or the leak that removed the ready to use hot, put you in sync with relying on a T&P that I've seen clogged completely shut in less than two years.


Did you all even realize that the mfg. of all water heaters require annual tripping of that valve, replacement after a couple years? That would be ideal but half the fools that install them, never install the drip leg down to the floor because they're too inept to understand any different.


I'm a code abiding plumber but I don't support weak arguments because they don't exist in print, in code. It's the probability standard along with years of experience knowing the what ifs in plumbing and how detrimental an okay or nod, an acceptance that since it isn't in the book that it's a go.

Total bullshit and you'll be held responsible for your bad advice if someone is killed for what we all know is a bad situation when thermal expansion becomes a multiplier for pressure and no weak links in the chain to break before the big one lets go.


Kudos to Ian, don't cowl down when you know you're right. That's something you'll never see from me in person or in print.

 

[Frenchie]

Because people are effing retarded most times when they have a leak in their home, and they start that chain reaction of shutting valves off until the leaks stop, not understanding that there's a water heater sitting there operating because they think the device shuts down when the water is turned off.

You had me at "retarded".

 

[GabeS]

Why don't they install high temperature shutoffs on hot water tanks like they do on boilers? Or expansion tanks on hot water tanks? They are closed systems, right?

Now I know to remove any valves on hot water side of hot water tank. I think that point has been made rather clear. I don't see any clear arguments why it should stay there.

The point about the water only reaching boiling water. In a closed system the water can heat up to a much higher temperature before it boils because it is under pressure.

Everyone keeps saying why would someone close both valves. I think it's obvious that the chances are very very low. But it only takes one exploision to kill someone.

 

[Dunbar Plumbing]

Why don't they install high temperature shutoffs on hot water tanks like they do on boilers? Or expansion tanks on hot water tanks? They are closed systems, right?

Now I know to remove any valves on hot water side of hot water tank. I think that point has been made rather clear. I don't see any clear arguments why it should stay there.

The point about the water only reaching boiling water. In a closed system the water can heat up to a much higher temperature before it boils because it is under pressure.

Everyone keeps saying why would someone close both valves. I think it's obvious that the chances are very very low. But it only takes one exploision to kill someone.

That would be ideal if there was high temperature shutoffs, but considering anything mechanical can and will fail, that's another device in the series of many that can protect only if it is working.


On expansion tanks, Code in KY states that the tee for the line for the expansion tank must be between the cold water shutoff and the top of the water heater. That way in the scenario if the cold water valve is shut off, the expansion tank is NOT isolated from the heater that is producing thermal expansion.


If a water heater produces a full tank of ready to use hot water, I can cut the lines off that tank at the top and water will "well" out of that tank for hours. That's why you can put your hand on the cold water inlet if no water has been used in the house for some time and the cold water inlet line will be warm/hot due to thermal expansion.


We shouldn't expect property owners to understand the particulars of plumbing. They just know it's broke when it doesn't work. That's why plumbers that are educated like us need to stand up to the plate and educate the masses of worst case scenarios because they do indeed happen. Was this the site that had the guy who ran new copper to the water heater and the top collapsed in because of a backflow device?

Could of been an even greater disaster and I believe the guy was so embarrassed after we did a pile-on that he didn't want to face the music how right we were, how deadly wrong his actions were. He had a family in that home as well.


So those of you dismissing these hazards, you're not speaking from the extensive knowledge a plumber posesses. I'm sure I can question the rhetoric of the rules you play by but somewhere in the mix you have to put case history into thinking.


Dual valves on commercial applications, large condo units, you know why?

Far less chance of "uneducated" hands ending up on those valves, even though bad things like hot reversal causing burns have happened in this mode when 1 of 3 units are down and a crossover occurs.

You're not going to have Miss Daisy trying her luck at stopping the leak in that scenario. In her home, yes, a large building....maintenance or plumber is coming.


Closed systems like a PRV on the main line, a common device nowadays. Dual Check Valve assembly = water comes in, never goes back out.

People misunderstand/underestimate plumbing and its hazards.

 

[Dunbar Plumbing]

You had me at "retarded".

LOL! I like the picture. I'll have to pay you royalties every time I use it.

 

[Probedude]

Why don't they install high temperature shutoffs on hot water tanks like they do on boilers?

They don't? My previous 3 have them.

 

[SewerRatz]

Ratz, what you're basically saying , then, is:

if there was a shutoff on the hot side, and if they shut it off, and also closed the (existing) supply-side shutoff...that would be really be dangerous... if or when something went wrong with the t&p valve.


Whereas if there isn't a shutoff on the hot side, they could only shut off the cold, and so if or when something goes wrong with the t&p, at least the seals on the faucets (hot or cold) can blow & let off some of the excess pressure?


I have to ask you why the hell anyone would turn off the inlet OR the outlet to a tank? What possible scenario you can see where someone would do that, unless they were swapping it out?

People do it all the time. Lets say they where changing a Moen cartridge on a shower valve that does not have stops. They turn of the water at the meter and turn of the valves at the water heater. There can be a ton of what ifs.



Probedude: 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. Now will this happen in every case. NO , in other cases like the picture of the water heater I posted the water was on and the water did get super heated and caused the tank to buldge.

In the car dealership where the rubbers did get melted everyone was lucky that (a) that the heater did not blow up (b) no one got hurt by the steam coming out of the fixtures. You know anyone that doesn't believe that a water heater that has a failed Pressure and Temperature valve and the thermostat does not shut down the heater is a danger you should go to Watts web site and order the free video Explosion - Danger Lurks. Also you should ask for the Danger - Scalding Lurks and heck just for grins Water Backflow Prevention.

Here is the link to the order form http://www.watts.com/pro/divisions/watersafety_flowcontrol/learnabout/learnabout_dvdorderform.asp