TRP Drain Line Question

[Peter Foxe Smothers]

Is the drain line from the TRP valve on a attic installed hot water heater allowed to drain in to the pan if the pan is plumbed

[David P. Valley]

yes, Peter

[Jeffrey R. Pope]

In LA it's allowed (per the IRC), but not in states where the UPC is enforced, such as CA.

[Peter Foxe Smothers]

Thanks!

[Emmanuel J. Scanlan]

NO!

2003 IRC:

P2803.6.1 Requirements of discharge pipe.
The outlet of a pressure relief valve, temperature relief valve or combination thereof, shall not be directly connected to the drainage system. The discharge from the relief valve shall be piped full size separately to the floor, to the outside of the building or to an indirect waste receptor located inside the building. In areas subject to freezing, the relief valve shall discharge through an air gap into an indirect waste receptor located within a heated space, or by other approved means. The discharge shall be installed in a manner that does not cause personal injury or property damage and that is readily observable by the building occupants. The discharge from a relief valve shall not be trapped. The diameter of the discharge piping shall not be less than the diameter of the relief valve outlet. The discharge pipe shall be installed so as to drain by gravity flow and shall terminate atmospherically not more than 6 inches (152 mm) above the floor. The outlet end of the discharge pipe shall not have a valve installed.

P2706.1 General.
Every waste receptor shall be of an approved type. Plumbing fixtures or other receptors receiving the discharge of indirect waste pipes shall be shaped and have a capacity to prevent splashing or flooding and shall be readily accessible for inspection and cleaning.

The standard pan used under a hot water heater is not acceptable to prevent the possibility of damage to the structure from a large flow of water, under pressure, when a TPR releases. If the pan were appropriately sized to prevent splashing and potential damage then it may be allowed.

[Jeffrey R. Pope]

I understand your logic Manny, but I'm not sure I agree with your interpretation.

The UPC is much more specific. . .

510.8 Relief Valve Discharge. Discharge from a relief valve into a water heater pan shall be prohibited.

[Emmanuel J. Scanlan]

Jeff,

Wish I had a copy of the UPC. Any links to an online version?

Basically what I am referring to is the size of most pans placed under water heaters are very meager. Most are barely big enough to hold a gallon or two of liquid and the edges are barely an inch high. If a TPR pops there is going to be a lot more water flowing than the pan can handle. Also it will wind up splashing everywhere when under pressure.

Probably a better explanation comes from the IRC Commentaries:

P2803.6.1 Requirements of discharge pipe. The outlet of a
pressure relief valve, temperature relief valve or combination
thereof, shall not be directly connected to the drainage system.
The discharge from the relief valve shall be piped full size sepa-
rately to the floor, to the outside of the building or to an indirect
waste receptor located inside the building. In areas subject to
freezing, the relief valve shall discharge through an air gap into
an indirect waste receptor located within a heated space, or by
other approved means. The discharge shall be installed in a
manner that does not cause personal injury or property damage
and that is readily observable by the building occupants. The
discharge from a relief valve shall not be trapped. The diameter
of the discharge piping shall not be less than the diameter of the
relief valve outlet. The discharge pipe shall be installed so as to
drain by gravity flow and shall terminate atmospherically not
more than 6 inches (152 mm) above the floor. The outlet end of
the discharge pipe shall not be threaded and such discharge pipe
shall not have a valve installed.


❖ Relief valves are emergency devices that are not in-
tended to operate continuously. Any discharge must
not go unnoticed, because discharge from a relief
valve indicates that something is wrong with the sys-
tem. The termination of a relief valve discharge must
be visible for observation so that corrective measures
can be taken as necessary.
If a relief valve discharges to a drainage system, the
discharge must be an indirect connection through an
air gap to prevent backflow from potentially contami-
nating the potable water system.
The diameter of the discharge pipe must not be re-
duced or be less than the diameter of the relief valve
outlet. Relief valve discharge piping must not be ex-
posed to freezing temperatures, since freezing water
could block the pipe and disable the relief valve. The
relief valve must first discharge through an air gap into
an indirect waste receptor located in a heated space,
which, in turn, terminates outside. The discharge pipe
must terminate close to the floor level to prevent harm
to building occupants. See Commentary Figure
P2803.6.1. Water must not be allowed to discharge
where it can cause structural decay. Discharge piping
must drain by gravity and must not be trapped within
the relief piping system. Standing water in the dis-
charge line may become contaminated. To discourage
any obstruction in the discharge pipe, the code prohib-
its the installation of a valve or threads on the outlet
end of such pipe.

[Jeffrey R. Pope]

As I said, I understand and agree with your logic, however, your interpretation is not in line with common understanding as I know it. I believe that most code authorities agree that it is acceptable to discharge into the drain pan when referencing the IRC.

[Russel Ray]

It's allowed down here in San Diego.

[Jeffrey R. Pope]

I assume you mean that some of the AHJ's turn a blind eye to it Russ. San Diego County follows the same California Plumbing Code as Los Angeles County.

[Emmanuel J. Scanlan]

Russel,

www.municode.com does not list San Diego but the San Diego County WEB site does provide a reference to their codes www.sdcounty.ca.gov/dplu then to www.amlegal.com/sandiego_county_ca/ . It appears San Diego county follows the California Plumbing Code which does prohibit this (see Jeff's reference above ).

[Russel Ray]

Originally Posted by jpope

I assume you mean that some of the AHJ's turn a blind eye to it Russ. San Diego County follows the same California Plumbing Code as Los Angeles County.

Not some. All.

Remember that the AHJ, and his/her interpretation, has the final say-so.

[Jeffrey R. Pope]

There's really no other way that this can be interpreted.

510.8 Relief Valve Discharge. Discharge from a relief valve into a water heater pan shall be prohibited.

I'm sure there are many AHJ's in San Diego County that abide by the CPC. After all, most of them have never known any Building Code other than the UBC/CBC.

[Russel Ray]

Originally Posted by jpope

There's really no other way that this can be interpreted.

Hmmmmmm.

If that were the case, we wouldn't be having this discussion. Witness:

Originally Posted by psmothers

Is the drain line from the TRP valve on a attic installed hot water heater allowed to drain in to the pan if the pan is plumbed

Originally Posted by dvalley

yes, Peter

Originally Posted by jpope

In LA it's allowed (per the IRC), but not in states where the UPC is enforced, such as CA.

Originally Posted by escanlan

NO!

2003 IRC:





The standard pan used under a hot water heater is not acceptable to prevent the possibility of damage to the structure from a large flow of water, under pressure, when a TPR releases. If the pan were appropriately sized to prevent splashing and potential damage then it may be allowed.

Originally Posted by jpope

I understand your logic Manny, but I'm not sure I agree with your interpretation.

The UPC is much more specific. . .

510.8 Relief Valve Discharge. Discharge from a relief valve into a water heater pan shall be prohibited.

Originally Posted by jpope

As I said, I understand and agree with your logic, however, your interpretation is not in line with common understanding as I know it. I believe that most code authorities agree that it is acceptable to discharge into the drain pan when referencing the IRC.

[Jeffrey R. Pope]

The IRC is not as clear as the UPC/CPC.

It is quite clear by California Standards.