Replacing old water heater
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Where I live you must put an expansion tank on no matter what, if your getting it inspected.
Ask your inspector if he’s ever removed an expansion tank that was in an open system and looked at and smelled the water that was in it.
If he hasn’t then tell him he should investigate it, find a few that’s 7-8 yrs old.
Code hasn’t caught up with reality.
user 32496
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Are you saying an expansion tank in an open system is good or bad?
user 32496
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I think you’re right! I’m going to have to figure out a solution for my circumstance. There isn’t a floor drain in the room but there is a washer drain right next to the WH. Is that suitable drain for the T/P valve line? Or would it be better to route it out the wall to the outside?
pasadena_commut
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Is outside just through the wall right next to the heater? In that situation I think having a (braced) pipe go straight down and stop, then 6 inches (or whatever is required) below it have a wide metal cylinder that is open on top and has a drain on the bottom. Use a slowly curving 2" (?, maybe bigger) pipe to drain and change the direction of flow and go out through the wall to an outlet pipe. (Big pipe because while the water coming out could flow at garden hose rates, it can only drain by gravity. Our washer drains into a sink with a 1.5" or 2" drain pipe. Big sink. It fills halfway up at the end of each rinse cycle, and yes, the drain is clear.) Be sure the outlet is in a place that cannot spray boiling water on anybody nearby. Like discharge it into a pile of rocks or down into a pit filled with gravel. Not sure how to handle the "keep the bugs/critters from coming up the pipe and into the room" problem. Some sort of metal screen halfway down the cylinder maybe?
I would have said to just pipe it straight through the wall and then aim down, but if memory serves, the code says it must discharge in the same room as the WH.
Is the washer drain in the floor? Is it 3" or 4" in diameter? Is it made of some material which can withstand 212F water? If so, I guess it would be an option. However, consider what would happen if it was even partially blocked.
In all honesty I don't recall having ever seen a house in my neighborhood where a TPR firing off wouldn't have destroyed something. (Correction, there is one. The WH is mounted to the wall in the alley next to the house, and there is literally nothing near it.) Even the ones where the WH is in the garage and discharges straight down onto the concrete floor are going to splatter water all over the place, I'm guessing 5' in every direction. If the garage was completely empty that would be it, but everybody has piles of crap in their garages and the bottom boxes, shoes, or whatever else is on that floor will be soaked. My house is tiny, but nearby there are some very big and expensive McMansions, and in some of those there are very expensive cars parked inches away from where the TPR for the WH in the garage would discharge. Can BMW bumper covers handle boiling water exposure?
I guess the compromise we are all implicitly accepting is that the plumbing will handle a leaking TPR valve, and if that valve is ever used in anger just be happy that there is "only" a lot of water damage and not a life threatening explosion.
I would have said to just pipe it straight through the wall and then aim down, but if memory serves, the code says it must discharge in the same room as the WH.
Is the washer drain in the floor? Is it 3" or 4" in diameter? Is it made of some material which can withstand 212F water? If so, I guess it would be an option. However, consider what would happen if it was even partially blocked.
In all honesty I don't recall having ever seen a house in my neighborhood where a TPR firing off wouldn't have destroyed something. (Correction, there is one. The WH is mounted to the wall in the alley next to the house, and there is literally nothing near it.) Even the ones where the WH is in the garage and discharges straight down onto the concrete floor are going to splatter water all over the place, I'm guessing 5' in every direction. If the garage was completely empty that would be it, but everybody has piles of crap in their garages and the bottom boxes, shoes, or whatever else is on that floor will be soaked. My house is tiny, but nearby there are some very big and expensive McMansions, and in some of those there are very expensive cars parked inches away from where the TPR for the WH in the garage would discharge. Can BMW bumper covers handle boiling water exposure?
I guess the compromise we are all implicitly accepting is that the plumbing will handle a leaking TPR valve, and if that valve is ever used in anger just be happy that there is "only" a lot of water damage and not a life threatening explosion.
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user 32496
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I wonder how common it is for the T/P valve to release water? I’ve never seen one or heard of one opening.
It’s not real common but it happens.
The T&P valve pops off for two reason and each of these conditions it pops off different.
High water pressure will cause it to dribble water.
High temp will cause it to pop off full flow and not close until the tank cools off. So you get a lot of water at once.
The most common reason I see a T&P pop off from heat is on electric water heaters from loose thermostats not contacting the tank and from a grounded element that heats 24/7.
user 32496
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Well...You made me research the code (not a bad thing) and here is what I found. We are in a IPC code area.
IPC 2018 - 504.6 Requirements for discharge piping.
The discharge piping serving a pressure relief valve, temperature relief
valve or combination thereof shall:
1. Not be directly connected to the drainage system.
2. Discharge through an air gap located in the same room as the water heater.
My understanding of the air gap is it is required only if you hook the T&P discharge to the waste system or some other concealed piping. When connected to a waste system, the purpose of any air gap is to prevent contamination of the water supply in case of backflow. The same as a dish washer. If your discharge goes to the floor or the pan, the airgap is not applicable.
3. Not be smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap.
4 Serve a single relief device and shall not connect to piping serving any other relief device or equipment.
5. Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor or to the outdoors.
6. Discharge in a manner that does not cause personal injury or structural damage.
7. Discharge to a termination point that is readily observable by the building occupants.
8. Not be trapped.
9. Be installed so as to flow by gravity.
10. Terminate not more than 6 inches (152 mm) above and not less than two times the discharge pipe diameter above the floor or flood level rim of the waste receptor.
11. Not have a threaded connection at the end of such piping.
12. Not have valves or tee fittings.
13. Be constructed of those materials listed in Section 605.4 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.
Note: Just about any material except PVC, which is odd because my old house had PVC.
14. Be one nominal size larger than the size of the relief valve outlet, where the relief valve discharge piping is installed with insert fittings. The outlet end of such tubing shall be fastened in place.
504.7.2 Pan drain termination Where a pan drain was not previously installed, a pan drain shall not be required for a replacement water heater installation.
****************
Even though it looks like T&P termination into the pan or onto the floor is acceptable by IPC, I can see that it would be catastrophic to have the T&P trip due to thermal over-run. I will be brainstorming for a solution just as soon as I clear a few other projects.
ICC Section P2902.3.1 sheds more light on the reasoning for the code concerning an air gap...
There are three reasons for the air gap to be in the same room as the water heater: (1) it prevents a direct connection to concealed discharge piping that might be bent, flattened, plugged, reverse-sloped or inadvertently capped off; (2) it provides a location for observing discharge when testing the relief valve and (3) it provides a readily accessible location to observe valve leakage indicating a defective T&P valve, a water distribution system overpressure problem, or a water heater operation problem.
further...
Water discharged from the T&P valve must be directed to one of four locations: 1. The floor below the water heater; 2. The water heater or storage tank drip pan, if present; 3. A waste receptor, such as a floor drain; or 4. The outdoors. The choice of discharge location must consider the potential for personal injury and structural damage that water discharge might cause. For example, a floor discharge might be suitable in a concrete-floored and curbed garage, but where the garage walls are of wood and rest directly on the floor, this discharge point might be unsuitable. Another suitable floor discharge example might be the tiled and sloped floor of a laundry/utility room that has a floor drain. Discharge to laundry trays/tubs and sinks would not be a suitable location as it violates the intent of Item 6 of this section, which is to protect the person using the fixture from hot water and steam that could come from the discharge pipe.
pasadena_commut
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Supposedly they don't open up very often. However, it is fairly common for them to leak (slowly) after testing one using the lever on top. I had one do that and had to replace it. The only positive thing I can say about that experience is that it was much easier to get the TPR valve out than it was to replace the sacrificial anode. A big wrench was good enough for the valve, whereas an impact wrench was needed for the anode.
Ludington
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Never could understand why the end of the discharge pipe can't be threaded. ???
I'm about to change the W/H for my neighbor, who was just diagnosed with liver cancer. He wants it connected the same way it was installed in 2004, but the 3/4" discharge is connected into the wall, and discharges on the floor of his patio by his front door. Seems that is not to code, so it looks like I too will just discharge into his pan in his garage, right?
To prevent someone from screwing a cap on it
I agree.
Why don’t they require a coupling soldered on the end of copper so a clown couldn’t slip a sharkbite on it ?
Ludington
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I guess there would always be someone that would do that. I wonder if the tank would just split, or blow up like a bomb.
A lot of them shoot out of the roof like a rocket. Some have blown the side of the house off.
I agree but these guys go by the book. Sometimes I wonder if they ever worked in the field.
user 32496
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Does the discharge line just go straight through the wall or is it concealed inside the wall and come out some distance away? What I'm getting at is...my interpretation of the code concerning concealed discharge piping is that you would need an air gap in case the concealed pipe was crushed, kinked, or otherwise blocked. If you can ascertain that the concealed pipe is not blocked, ie. it just goes straight through a wall and you can see the other end of it, I wouldn't be worried about installing an air gap.
I think discharging to the outside is far better than discharging to the pan.
pasadena_commut
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The layout isn't clear from your description. Is the tank next to a wall that has the patio on the other side, so that the existing pipe is short and goes straight through the wall, or does the pipe take some other, longer, path to that patio?
Where does the existing pan drain to?
If "outside" is on the other side of one of the garage walls you could have the TPR discharge through an air gap into something like a small metal garbage can (several gallons capacity and watertight) and then run a fairly large diameter drain from that can to the outside. Not sure how to keep critters from coming back up that pipe and into the can. A metal screen part way down would work - the water would go right through but a rat, not so much.
If the tank is in a corner and the outside isn't nearby, I suppose one could also run a pipe or other channel along the floor next to the wall of the garage from the can to empty near the door. Moving it inward away from the wall would be too much of a tripping hazard.
The w/h is in the center of his 3 car garage, against the back wall. The tpr comes out of the top of the tank, goes halfway down the side, then goes horizontally into the drywall. From there, it is anyone's guess, since in on direction, it could connect into the sewer line, and the other direction, it could discharge onto the front porch area. The guy wants me to hook up the new w/h just as the old one was installed, back in 2004. BTW, he has no pan under the w/h currently.
