Shutoff Valve in Hot Water Line of Water Heater

**Ian Gills** · 12-18-2008, 02:28 PM

I have checked and it would not appear to be against code everywhere, as I originally assumed. Sorry. In Illinois for example it appears to be allowed.

But I maintain that it is dumb to have two shut-offs on a WH. If you the plumber have put a ball valve on the hot you have opened the door for human nature to injure someone.

They possibly would not want to call a plumber when the T+P is working properly and releasing water.
They put a cap on the T+P "I can fix this honey"...
The heater builds up excessive pressure and pinholes a weld on the tank...
They close both valves and know it is now time to call you to replace the heater...
You pull up to a house with a bunch of emergency vehicles in front of it because the homeowner never turned off the gas,"It wasn't what was leaking"
With hot open maybe they will have a chance blowing a water supply.

Yes, there might be exceptions. From my 365+ days of plumbing experience as a fully qualified and master homeowner, I would guess that on a residential 2 heater parallel installation, installing a hot and cold on each heater might be essential. When 1 heater takes a dump, that heater can be isolated, and the other heater will work without the leaker leaking.

But I maintain that traditionally a 1 tank residential heater will only have a cold water valve.

A tankless might require both a cold and hot shut off with bypass valves to allow for flushing though.

**jar546** · 12-18-2008, 04:24 PM

Ian,

It is not against code to add a shut off on the hot water side and it makes it easier to service the equipment. The TPR valve is what protects the equipment. If you don't have one and all of the hot water fixtures are in the off position, it is no different than having a valve installed on the hot side and in the closed position.

I understand your concern and appreciate your passion but you are incorrect.

I think you need to specify the code that prohibits this, otherwise you are misleading people with false information.

A shutoff valve is required on the cold water side per the IPC and IRC. In the IPC it can be found in 503.1 and in the IRC it is in P2903.9.2

I have supplied you with direct references, now I ask the same from you.

**jar546** · 12-18-2008, 04:31 PM

Also,

You cannot fix stupid and keep people from injuring themselves due to their own negligence. It is bad enough that we have to have stickers on lawn mowers telling people that they are not hedge trimmers because some moron picked up a mower to trim his hedges and won a lawsuit.

Under normal operating conditions, the valves will be in the open position.

Again, as long as you don't have water running in the house, there is no difference between that and a closed valve on the hot side. Either way the water is restricted and pressure can build up, hence the need for a TPR valve.

If you are stupid enough to cap the TPR, leave the gas on and turn off both valves then you don't belong in society anyway.

If you don't like it then don't do it in your house. It is not required but it certainly is not against any nationally recognized codes.

**Ian Gills** · 12-19-2008, 09:38 AM

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.

**GabeS** · 12-19-2008, 10:48 AM

I'm with jar on this one. I don't see how a closed faucet or shower head is any different from a closed valve. I guess Ian is suggesting that a soldered copper elbow is a weaker connection than a valve and would burst before the tank would as opposed to a ball valve not bursting in a high pressure situation. This may or may not be correct, but I can't imagine a huge difference in strenght between the two.

Also, I believe a bigger concern would be to have threads on the bottom a T&P extension pipe, where a unfamiliar homeowner would even have the ability to cap it. Absolutely no threads allowed on the bottom of that pipe.

A hot water side valve would allow you to change the water heater without having to drain all the hot water lines.

**burleymike** · 12-19-2008, 11:39 AM

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

**Basement_Lurker** · 12-19-2008, 02:03 PM

Originally Posted by Ian Gills

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.

hj · 12-20-2008, 02:04 PM

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** · 12-20-2008, 04:33 PM

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** · 12-20-2008, 04:56 PM

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** · 12-20-2008, 05:19 PM

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

**Verdeboy** · 12-20-2008, 05:22 PM

Originally Posted by 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.

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** · 12-20-2008, 05:38 PM

Originally Posted by jar546

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** · 12-20-2008, 05:42 PM

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** · 12-20-2008, 06:08 PM

Originally Posted by 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?

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.