# Water Heater Relief Valve Discharge Piping



## Michael.L (Nov 26, 2019)

2015 IPC 504.6 states:
The discharge piping serving a pressure relief valve, temperature relief valve, or combination thereof shall:
2. Discharge through an air gap located in the same room as the water heater.
5. Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor, or to the outdoors.​I have seen many, many installations where the water heater relief valve discharge pipe passes through a wall before discharging. The most common is when the water heater is located against an exterior wall and the discharge pipe passes through the wall and discharges above the ground outside the building. But I have also seen installations where the water heater is in a small enclosure (mechanical room, water heater closet, etc) and the discharge pipe passes through the wall of that enclosure and empties above a floor drain, floor sink, or mop sink in an adjacent room.

Are all these improper installations? If they are, they seem to be so common that they are practically accepted as a legal variance of the code.


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## steveray (Nov 26, 2019)

I think hey make them do that in Cali, I recall a bunch of ICE pics....You can dump it in the pan and then indirect to anywhere you want.....


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## Rick18071 (Nov 26, 2019)

Michael.L said:


> Discharge through an air gap located in the same room as the water heater.



If you do not understand this simple requirement ask the ICC for an interpretation.

If the water went somewhere else the home owner would never know that there is something wrong..


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## Pcinspector1 (Nov 26, 2019)

So many water heaters are installed without permits I suspect is the reason. I have had water heaters installed in my homes in the past, the contractor's don't bother with getting permits. 

Here, I tell residents that call that there's quite a few things to inspect on a WH! 

Venting flue pipe and clearances, union, valves, drip or dirt leg, gas line types and support, bonding CSST, pre-made appliance connectors with required tag, seismic straps, location, clearances, serviceability and then there's electric type WH issues like disconnect location, breaker size and conduit to the ceiling. 

The violation I see the most is the wrong discharge piping being used, usually PVC or PEX that has an insert fitting reducing the inside size. There are pre-made discharge pipes with a threaded end and you can still use CPVC. 

I thing the installers do the best they can to comply when permitted.


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## ADAguy (Nov 26, 2019)

"When"? or "If"?


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## classicT (Nov 26, 2019)

Michael.L said:


> 2015 IPC 504.6 states:
> The discharge piping serving a pressure relief valve, temperature relief valve, or combination thereof shall:
> 2. Discharge through an air gap located in the same room as the water heater.
> 5. Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor, or to the outdoors.​I have seen many, many installations where the water heater relief valve discharge pipe passes through a wall before discharging. The most common is when the water heater is located against an exterior wall and the discharge pipe passes through the wall and discharges above the ground outside the building. But I have also seen installations where the water heater is in a small enclosure (mechanical room, water heater closet, etc) and the discharge pipe passes through the wall of that enclosure and empties above a floor drain, floor sink, or mop sink in an adjacent room.
> ...


Is this per your State's amendments? Non-amended IPC below.

*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.
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.​


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## ICE (Nov 26, 2019)

This is California plumbing code.  One difference is that the smitty pan is out.   Another is the height above a floor. 

608.5 Discharge Piping. The discharge piping serving a temperature relief valve, pressure relief valve, or combination of both shall have no valves, obstructions, or means of isolation and be provided with the following:

(1) Equal to the size of the valve outlet and shall discharge full size to the flood level of the area receiving the discharge and pointing down.

(2) Materials shall be rated at not less than the operating temperature of the system and approved for such use.

(3) Discharge pipe shall discharge independently by gravity through an air gap into the drainage system or outside of the building with the end of the pipe *not exceeding 2 feet (610 mm) and not less than 6 inches* (152 mm) above the ground and pointing downwards.

(4) Discharge in such a manner that does not cause personal injury or structural damage.

(5) No part of such discharge pipe shall be trapped or subject to freezing.

(6) The terminal end of the pipe shall not be threaded.

(7) Discharge from a relief valve *into a water heater pan shall be prohibited. *


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## e hilton (Nov 26, 2019)

ICE said:


> (7) Discharge from a relief valve *into a water heater pan shall be prohibited.
> *
> Whoops.  Every WH i see around here, the discharge pipe points straight down from the t&p valve, and ends a couple of inches above the overflow pan.


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## e hilton (Nov 26, 2019)

Well i messed up that quote somehow.  Sorry.


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## ICE (Nov 26, 2019)

If you consider that the volume of the pan is mostly filled with water heater......the pan is shallow......the discharge will hit the pan and not stay in the pan.  If the pan were empty and the drain pipe was high enough to not have blow-back, the pan drains by gravity and the T&P would overwhelm it right away.






This one was dripping.  They do that before they fail.


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## e hilton (Nov 26, 2019)

I think the intent of the pan is to catch water from a leaking tank, and drain it to the outside.  The t&p discharge is just conveniently pointed into the same pan. In the first picture, at least they have a drain hose connected, most i have seen do not.  Like the second picture.


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## ADAguy (Nov 26, 2019)

Good stuff, thank you


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## Michael.L (Nov 26, 2019)

Rick18071 said:


> Michael.L said:
> 
> 
> > Discharge through an air gap located in the same room as the water heater.
> ...


I fully understand this "simple requirement"; I just think it's stupid and misguided. Apparently this was a recent change in the code (sometime around 2007) which would explain the many, presumably older, installations I've seen where the air gap is located outside the room where the water heater is installed.

Insisting that the air gap is located in the same room provides NO assurance that the property owner will "know that there is something wrong." For example, many water heaters are installed in unfinished basements or attics. How many people hang out in their basements or attics all day watching their water heater relief valve discharge pipes? I've seen an installation where the water heater is in a dedicated enclosure off the laundry room and covered by a wood panel with four retainers (not a door); the retainers were little metal tabs that had to be rotated out of the way to remove the cumbersome panel to access the heater. How many people do you suppose open that on a regular basis to check the status of their discharge pipes? I've seen water heaters in commercial buildings that are installed in locked dedicated water heater closets. Again, they are not at all visible to anyone during normal daily routines. Even maintenance and cleaning crews wouldn't normally check on them.

In every one of these scenarios, the water heater would not be observed for months, and in most cases, would not be observed in years. So explain to me how this "simple requirement" actually makes anything safer or better than before? The requirement for _"Discharge to a termination point that is readily observable by the building occupants"_ is a much more sensible and useful requirement.

You might argue that the new code is good because it demands both (air gap in same room AND termination point readily observable). But the reality is that the requirement for the termination point to be observable means that any termination point that is not the air-gap-in-the-same-room, must itself be either an air gap or air break: direct plumbing wouldn't be observable. This means the piping between the air-gap-in-the-same-room and the termination point will be a gravity drain. Since no one is going to plumb that in 2" piping, it will quickly be overwhelmed by any substantial discharge from the relief valve. So now the air-gap-in-the-same-room will overflow and you will have scalding hot water flooding whatever room the water heater happens to be installed in. What a great idea for attic-installed water heaters! Imagine if that water heater quickly relieves 50 gallons of 140+°F water onto the drywall ceiling of a bedroom over some sleeping occupants.

I also take issue with the code change that allows discharge into the water heater pan. As ICE pointed out, a water heater pan with it's 3/4" gravity drain, would quickly be overwhelmed by any substantial pressurized flow from a "popped" relief valve. And if the valve is weeping (as is often the case), then you will have a puddle of water that the water heater could be standing in for months, rusting out the bottom, while no one's the wiser.

Most times, the code creators get things right. In this case, I contend they got things horribly wrong.


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## e hilton (Nov 27, 2019)

Michael.L said:


> _"Discharge to a termination point that is readily observable by the building occupants"_ g.


When i was in texas 20 yrs ago, placing hvac units in the (blistering hot) attic was common.  The drain tube from the overflow pan was usually located over the front door, the idea being that if there was water dripping out of the tube the homeowner would more likely see it.


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## ADAguy (Nov 27, 2019)

And slip and fall if it did?


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## Rick18071 (Nov 27, 2019)

Michael.L said:


> I fully understand this "simple requirement"; I just think it's stupid and misguided. Apparently this was a recent change in the code (sometime around 2007) which would explain the many, presumably older, installations I've seen where the air gap is located outside the room where the water heater is installed.
> 
> Insisting that the air gap is located in the same room provides NO assurance that the property owner will "know that there is something wrong." For example, many water heaters are installed in unfinished basements or attics. How many people hang out in their basements or attics all day watching their water heater relief valve discharge pipes? I've seen an installation where the water heater is in a dedicated enclosure off the laundry room and covered by a wood panel with four retainers (not a door); the retainers were little metal tabs that had to be rotated out of the way to remove the cumbersome panel to access the heater. How many people do you suppose open that on a regular basis to check the status of their discharge pipes? I've seen water heaters in commercial buildings that are installed in locked dedicated water heater closets. Again, they are not at all visible to anyone during normal daily routines. Even maintenance and cleaning crews wouldn't normally check on them.
> 
> ...



I agree with you but until the code changes I will inspect to code. There are a lot of things in the code I don't agree with.


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## ICE (Nov 27, 2019)

2. Discharge through an _air gap _located in the same room as the water heater.
That works if there is a laundry sink....other than that ....I doubt it.

5. Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor or to the outdoors.
The garage floor is a last resort that I have reluctantly allowed when it was that or no hot water.  The thing with the pan serving the water heater tells me that the committee in charge of this code  didn't get it and that's why there is a number two.

Michael.L,
I have never heard of a T&P operating because there was too much pressure or too high of a temperature.  On the odd chance that it did happen I want it to function.  Through an air gap or into a pan will not work.

I should clarify: An air gap could be made to work.  At the point of the gap the mechanics of a gravity drain take over.  Given a pipe of sufficient diameter with few twists and turns....well then maybe.

So as Rick pointed out, you have a code to contend with.  A stupid code.  I myself know how to contend with a stupid code.....That would be to confab with the Chief Plumbing Engineer and reach an agreement....or at least let him know what I was up to.


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## Michael.L (Nov 27, 2019)

ICE said:


> I have never heard of a T&P operating because there was too much pressure or too high of a temperature.  On the odd chance that it did happen I want it to function.  Through an air gap or into a pan will not work.


I agree about wanting it to work. Absolutely! Safety is the primary concern.

I have seen T&P valves discharging due to excessive pressure (no expansion tank). Granted, it was a dribble, not a blast. But it's not an uncommon problem.

I've also seen a water heater that burst due to excessive pressure (again, no expansion tank). It was not a Mythbusters style explosion, but it was catastrophic (i.e., the tank split open). Fortunately, that was in the unfinished basement of a hillside house, so no flooding or other serious damage occurred. (But imagine if that happened when the homeowner was away on vacation and the gushing water washed out a section of the supporting hillside!) In this case, the T&P valve discharged through the exterior wall of the house to an air gap over the ground outside. No matter: no one would have seen it if the air gap was inside next to the heater.



ICE said:


> I should clarify: An air gap could be made to work.  At the point of the gap the mechanics of a gravity drain take over.  Given a pipe of sufficient diameter with few twists and turns....well then maybe.
> 
> So as Rick pointed out, you have a code to contend with.  A stupid code.  I myself know how to contend with a stupid code.....That would be to confab with the Chief Plumbing Engineer and reach an agreement....or at least let him know what I was up to.


So I am building-out a small commercial space. The water heater will be in a utility room located in the back adjacent to the kitchen. Inside the kitchen area, there will be a mop sink located against the common partition wall that separates the kitchen from the utility room. I intend to have the T&P relief pipe pass through this common wall and discharge via an air gap into the mop sink. If the T&P valve starts weeping, it WILL be seen almost immediately by the kitchen staff because it's in plain sight of a workspace that's used throughout the day. If the air gap and drain were in the utility closet, who knows when a discharge would be seen. As far as I'm concerned, I'm meeting the spirit of the code, if not the exact language of the code. And I'll argue anyone that my installation will be safer and minimizes the risk of personnel and property damage compared to following the "letter of the law."

Btw, the water heater pan drain will also discharge into the mop sink via an air gap drain pipe separate from the T&P discharge pipe. According to the "letter of the law" I could just dump my T&P valve discharge into the water heater pan. Then I would only have to install the single drain from the pan to the mop sink. Perfect code compliance! But what's the purpose of the pan in the first place? To prevent water damage in the event of a water leak. What's the point of that requirement when you have the potential of dumping many gallons of water into the pan and quickly overwhelming its 3/4" gravity drain?

The code is at odds with itself.


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