# Water  Heater  T & P  Valve  Drain  Line



## north star

** * * **

I'm looking for discussion and input from you all......On the T & P valves,

what size and type of piping are you seeing installed?

From my observations, on most [ typical 40 gal. sized ] water heaters, the

T & P valve has a 7/8" sized opening......If the opening is 7/8", can you

[ by the letter of the code - referring to Section 704.2 and / or 504.6,

Item # 3, 2006 IPC ], install 3/4" sized cpvc or 3/4" pex and be

compliant?

My contention is that if the 3/4" cpvc is installed, that the inside

diameter has indeed been reduced in the direction of flow, and

reduced in size smaller than the opening of the T & P valve.

Thoughts...

FWIW, ...as some may remember, the missing "Uncle Bob" used to be

very adamant about this requirement........Even on the use of 3/4" pex.

Thanks for your input!



** * * **


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## rshuey

We allow 3/4 CPVC or copper. We do not allow 1/2" CPVC or copper.


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## jeffc

The pressure relief valve exit is threaded and the 7/8 inner diameter is presumed that a threaded fitting will reduce the inner bore to 3/4".  I think the concern about the pipe size reduction occurs with Pex pipe. The Pex has internal fittings that reduce the inner bore of the pipe from 3/4" to 9/16", A reduction of area by over 50%.


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## Pcinspector1

Agree with rshuey and jeffc in both cases.

Will not allow garden hose either!

pc1


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## DAYWALKER

In illinois.....cpvc not allowed. Copper, iron pipe....etc. The thinking is the cpvc will melt.


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## Daddy-0-

We allow CPVC but not PVC. 3/4" is also allowed.


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## peach

PVC isn't listed for water supply (hot water)... CPVC is... water distribution piping is what is required.  I don't know that you'd want to allow a reduction in the discharge diameter regardless of the material used.


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## north star

** * * **

peach,

My thoughts exactly!......Plus, I want to know it if I am

incorrect [ according to the letter of the code ].

I actually measured the inside diameter of the 3/4 " cpvc

piping, ...it is 5/8" in diameter.

So, the question still is being posed......How many of you allow

this diameter reduction [ down to 5/8" i.d. ] in direct

disagreement with Section 504.6, Item #3, [ `06 IPC ]?

The reason that I am asking is that I have recently been

challenged on this requirement, in a Commercial application.

Your thoughts are encouraged and very much appreciated!

** * * **


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## Rider Rick

The T&P valve manufacturer Watts require 3/4" ID from valve to the end of the discharge line.

3/4" CPVC and Pex do not meet this requirement.


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## David Henderson

If the ID is 7/8" how in the world would you get a 7/8" discharge to the termination point without a bushing that would create a sort of bottle neck if you will?


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## north star

** * * **

David Henderson,

Good question!....I am not the manufacturer or associated with any

manufacturer, so what I am saying is only my opinion and experience.

IMO, the 7/8" opening at the T & P valve itself starts out with

the intention that any size of plumbing fitting [ an "increaser" or

a "reducer" ] will reduce the opening, at the T & P valve, down to

a designed 3/4" opening dimension......This "designed" 3/4" opening

is the dimension that is the dimension that is not to be reduced

over the length of the drainage piping.

Obviously, there will be some type of fitting attached to

the T & P valve to install the drainage piping to the point

of disposal......Sinced this specific installation point is not

addressed in the IPC or the IRC, and the fact that if the T & P

valves does open [ under pressure I am concluding ], I am erring

on the side of providing more piping diameter to accomodate

this pressure & hot water release rather than lesser piping

diameter......Also, I am taking in to consideration of Section

504.6, Item #6: Discharge in a manner that does not cause

personal injury or structural damage.

With a smaller diameter pipe, the probability of providing

a larger / greater sized bottleneck of pressure would be

created.....Again, IMO!......I would not want to utilize

the "god clause" provided in Chapter 1 - Section 102.9, `06

IPC, but I would want the system and its components to

operate in a safe manner.......I would encourage and review

any engineering reports or ICC ES Reports submitted in

rebuttal for using 3/4" cpvc or pex, ...or even 1/2" cpvc

or pex, ...or even 1/4" cpvc or pex [ "tongue in cheek" ].

Since we are discussing the "letter of the code" [ which is

what I asked for ], let us take into consideration all aspects

of the "letter"......If someone wants to install something smaller

than the 3/4" inside diameter, then please submit the appropriate

reports that will allow it.........Some on here might say that by

using this clause, I am abusing my position......I would

respectfully counter with "It is my intention to provide the

safest operation of the components installed.......If your

submitted data will support a smaller sized pipe, then I will

go by what the elected officials and AHJ leaders direct me to

do.".....Until directed otherwise, I will require a larger sized

inside diameter of the drainage piping and not worry about

the contractor or homeowner who is attempting to save money

on a smaller sized pipe.......No disrespect to you or others!

Also, if there is another means to attach approved sized

materials for this pressure relief valve, ...please list it on

here so I can learn about approving another type of

installation,  ...as approved by the manufacturer of the

T & P valves.

Thanks!



** * * **


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## mtlogcabin

Good article on T & P installation mistakes http://www.ashireporter.org/articles/articles.aspx?id=1568''>http://www.ashireporter.org/articles/articles.aspx?id=1568' rel="external nofollow">

http://www.ashireporter.org/articles/articles.aspx?id=1568


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## north star

** * * **

Thanks " mtlogcabin "  for the article......It's a good read!   

Also, "Much Thanks" to Uncle bob for his passion on

plumbing and other codes as well.   [ Hoping that you will

reconsider and rejoin this code forum Uncle Bob ! ].

** * * **


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## mtlogcabin

The inside diameters between the copper, iron or CPVC is miniscule. I agree with Post #3 with regards to the 7/8" size you are measuring.

http://www.gizmology.net/pipe.htm

http://www.engineeringtoolbox.com/pvc-cpvc-pipes-dimensions-d_795.html


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## Pcinspector1

IMO I don't believe PEX plumbing meets any required working tempatures for a T&P and the inside dia. of 3/4" PEX is 0.677 and that's before the insert fitting is added that reduces flow even further like an hour glass or like your postrate.

The closest Working temp. of PEX, 100PSI at 180degrees F does not meet the T&P pressure valve requirements.

pc1


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## north star

** * * **

Pcinspector1 ( and others ),

Can you please provide documentation / a link regarding the

PEX non-compliance!......I will need it to defend my position

of "not" installing it on T & P valves......The plumbers around

here will just love it when they cannot use it on T & P valves

any longer.

*& & & &*


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## Pcinspector1

north star,

Try the ICC-ES/ESR-1929 report.

3.1 Tubing pressure-rated for 100PSI @ 180 degrees and the insert fitting reducing the flow dia.

also see 4.2 about PEX should not be uses within 18" above the water heater on the supply side.

Our water heater at work has a WATTS 3/4" 100XL, 150PSI- 210F max. T&P which is pretty common I think? Would'nt the pipe melt or get soft if the T&P was to discharge?

pc1


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## Mule

The securing of PEX could also be a problem when using it on T&P valves.

Also doesn't most T&P valves require rigid pipe???? PEX is not a rigid material! Just thinking.....


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## north star

** * * **

Pcinspector1 ( and others ),

The Zurn [ brand ] PEX tubing can be installed on T & P

valves according to their manufacturers installation

literature.....See Page 23 in this link.

*http://www.zurn.com/images/pdf/zpm07199.pdf*

_" _Water _Heater Temperature and Pressure Relief Valves_


Zurn PEX tubing may be used on the discharge side of a

typical water heater temperature-pressure relief valve."


​I'm thinking that there are different types of

manufactured PEX tubing, ...with different design

characteristics.

So, should we be allowing the pex on T & P valves or

not, ...whether Commercial or Residential?



** * * **


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## Pcinspector1

north star,

Just goes to show you what I know. I'll start looking for the external PEX connection fittings that will no doubt be designed next to prevent the flow from being reduced from 3/4"

pc1


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## north star

*& & & &*



Pcinspector1,

That's o.k.!......At least you are trying to help in my search for information

and application of the published codes.

Thank you ( and the others ) who are assisting!  :agree

FWIW, the Zurn web site also has some opportunities for FREE online

CEU seminars - *http://www.zurn.com/pages/education-main.asp*

*% % % %*


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## Mule

2009 IPC 504.6 Requirements for discharge piping. The discharge

piping serving a pressure relief valve, temperature relief valve

or combination thereof shall:

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.

TABLE 605.4

WATER DISTRIBUTION PIPE

Cross-linked polyethylene (PEX) plastic tubing ASTM F 876; ASTM F 877; CSA B137.5

Cross-linked polyethylene/aluminum/cross-linked polyethylene (PEX-AL-PEX) pipe ASTM F 1281; ASTM F 2262; CAN/CSA B137.10M

Cross-linked polyethylene/aluminum/high-density polyethylene (PEX-AL-HDPE) ASTM F 1986

Code allows PEX however it must be secured according to specifications. What is that????? Every 32"............. Wonder if it 90's straight down...do you want to screw a fastener into the water heater? Does it require rigid pipe???


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## north star

*& & & &*



Section 504.6 [ from the `06 IPC ] does not provide Table 605.4

for application of fastening / support of the pex type tubing.

I could not "require" the 32 inch fastening dimension!



Beginning in the `09 IPC,  ...it does require the 32 inch fastening

dimension......I wonder how the plumbers will be anchoring the

pex tubing with this "new" requirement...



*$ $ $ $*


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## Mule

504.6 # 13 specifies that the discharge pipe of the T&P be constructed of materials specified in Table 605.4. Table 605.4 lists PEX as one of the materials allowed for T&P discharge pipes.

I would think it was sanitary also however the code refers you to water distribution......

I think the rigid pipe come from the manufacturers recommendations....... I think.... I'll do a little more research! But I may also be having flashbacks from the 70's!


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## Mule

504.6 # 6.....6. Discharge in a manner that does not cause personal

injury or structural damage.

If you use PEX (flexible) then it would be possible for the pressure relief valve to cause personal injury if not secured.

Still looking about the rigid stuff............


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## north star

** * * **

Agree on Item #6, from Section 504.6 [ `06 IPC ], ...unfortunately,

in most cases, the plumber that did the install is not around to incurr

those [ possible ] personal injuries, and most homeowners and a lot

of inspectors are not aware of the fastening requirements and the

amount of potential damage / injury that is possible with a fully

discharging T & P valve line.

In days gone by, it used to be common practice to install a 3/4"

copper [ rigid ] drain line on the T & P valves.

*& & & &*


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## skipharper

1) In years past the plumbing code said all pipe sizes are inside diameter (I.D.)

2) 3/4 pipe is 3/4 pipe regardless of the material

3) Refer to strapping requirements from Chapter 3 (pex every 32") small screw in water heater jacket

Burn your energy on Chapters 4, 7, and 9

Just my thoughts.............


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## Mule

skipharper said:
			
		

> 1) In years past the plumbing code said all pipe sizes are inside diameter (I.D.)2) 3/4 pipe is 3/4 pipe regardless of the material
> 
> 3) Refer to strapping requirements from Chapter 3 (pex every 32") small screw in water heater jacket
> 
> Burn your energy on Chapters 4, 7, and 9
> 
> Just my thoughts.............


Skip,

By reading this is it my understanding that you allow PEX to be used on T&P drains?

It would be interesting to see how many others allow PEX.


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## skipharper

Based on the water distribution table and the fact that my staff only enforces the language of the code (no what if's allowed) leaves no choice.


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## north star

*& & & &*

Mule,

Our AHJ allows pex also, but we require the minimum inside diameter to

be at least 3/4"......That typically means that 1" sized pex, with the

"inserted type" of fitings to be installed.....As Skip has stated, pex is

allowed by the IPC code.

*& & & &*


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## Mule

We allow it also. However there are jurisdictions around ours that do not.

We allow the 3/4" pex because somewhere I remember something about the fitting being "nominal" sized. Which inmy opinion if it is a 3/4 fitting then it's 3/4".

Also ..... which don't make any sense .... the opening for the actual valve on the inside is only about a 1/4" in diameter. So why would a fitting smaller than 3/4" make any difference? Volume?

Also for some reason I seem to remember something about pex not being allowed within 18" of the valve because of ????????? Or am I having flashbacks of the 70's?

Skip, A screw in the jacket? Would that void the manufactuers warranty? Just throwing out some thoughts.


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## skipharper

They say if you remember the 70's you weren't there!!! I do not believe the screw (small naturally) is an issue. I wonder how many folks require a 1" pex to a 3/4" hose bibb? I think the coke used to say nominal Mule however at 56, I have many strange flashbacks!!!


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## skipharper

See there--meant code!!!!!!!!!!!!!!!!!!


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## Glennman CBO

Don't have the code section handy, but in the '09 UPC, pex is not allowed to be installed within 18" of the water heater.

Therefore, I do not approve pex as a T&P line, or as a direct connection for the water supply or output.

Has anyone ever checked the listing of the pex in this regard?


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## Mule

From a pex website. http://www.ppfahome.org/pex/faqpex.html

What are temperature limitations for PEX?

PEX tubing can be used up to 200° Fahrenheit for heating applications. For plumbing, PEX is limited to 180° F. Temperature limitations are always noted on the print line of the PEX tubing.. PEX systems are tested to and can be used with standard T and P relief valves that operate at 210” F and 150 psi.

To me this doesn't make sense. PEX is limited to 180° F but can be used with standard T&P that operate at 210°. They do indicate that it HAS been tested though....


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## north star

*& & & &*

Glennman ( and others ),



Wonder why the IPC allows it and the UPC does not?   

*& & & &*


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## mtlogcabin

> To me this doesn't make sense. PEX is limited to 180° F but can be used with standard T&P that operate at 210°. They do indicate that it HAS been tested though....


The 180 degrees would be sustained use. When a T&P goes off at 210 it will discharge the hot water/steam for a short period of time. A 3/4" water line will flow about 25 GPM's at 60 PSI. Therfore the pex would not be subject to high temps for prolong periods of time.

JFYI we do not allow it here based on the UPC as glenman pointed out


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## north star

*& = & = & = &*

From the Zurn PEX Installation Guidelines.......See Page 23 for

water heaters.

*http://www.zurn.com/images/pdf/zpm07199.pdf*



*& = & = & = &*


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## skipharper

Good find North Star--the concern is with the B Vent from gas water heaters. I think this holds true with any plastic water distribution tubing for obvious reasons. The relief line is allowed to be pex per the instructions which match the plumbing code. The only issue left would be the pipe size which to me, if it's 3/4", its 3/4".


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## north star

** * * **

Skip,

What is the actual inside diameter of 3/4" pex tubing / piping...

Also, what is the inside diameter of the "inserted type" fittings

installed inside of the 3/4" pex tubing / piping?

Has the "diameter of the valve" served been reduced by the

use of 3/4" pex.......Our forum friend "Mule" stated that he

thinks that that valve is 1/4" in dimension.

Your thoughts...

** * * **


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## skipharper

While I have never measured these it is quite obvious to me that the inside diameter is smaller than 3/4". I simply use the rule of thumb that if you go into a supply house and ask for a pex male adapter in 3/4" thats what you will get. My personal opinion is if indeed the water heater relief line is blowing off due to pressure, and you use a 3/4 T & P with 3/4 pex x MIP adapter the intent of the code is met. In years past you could have seen a 1/2" sweat x 3/4" MIP adapter and that to me is what the code is trying to avoid. I do realize that in essance that is what has been created using pex however I lean on just reading the code book to my staff and do not add design thoughts, etc. to the code language. The books are already thick enough!!


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## mtlogcabin

The terms _PEX pipe_ and _PEX tube_ have been used interchangeably, however some manufacturers distinguish beween the two by manufacturing to different inside/outside diameters. For example, PEX pipe may be manufactured to IPS-ID (iron pipe size, inside diameter controlled) sizes with varying thickness to meet pressure requirements, while PEX tube may be manufactured to CTS-OD (copper tubing size, outside diameter controlled) sizes, commonly with a standard thickness of SDR-9 (standard dimension ratio).

What is the concern you have? The code allows copper or schedule 40 pipe which have different ID's which PEX uses the same national standard sizes.


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## north star

** * * **

mtlogcabin,

If the question is being posed to me, my concern is that the

smaller sized pipe / tubing does not meet the letter or the

intent of Section 506.4, #3, `06 IPC.....That a "bottle neck"

[ if you will ] is created by installing a smaller diameter

piping......From the angry plumbers in this AHJ, they believe

that they are compliant by installing the 3/4" pex tubing with

the insertable type fittings......I would like to know which is

the compliant installation.

Glennman CBO,

From the WattsPEX web site, see Page 6: Water Heaters

and Boilers......This particular manufacturer requires the 18"

separation from water heaters.



*http://media.wattswater.com/IS-WaterPEX.pdf*



** * * **


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## skipharper

mtlgcabin, I agree with the plumbers Sir.


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## skipharper

Meant Northstar, sorry, almost beer time!!


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## mtlogcabin

north star said:
			
		

> ** * * **mtlogcabin,
> 
> If the question is being posed to me, my concern is that the
> 
> smaller sized pipe / tubing does not meet the letter or the
> 
> intent of Section 506.4, #3, `06 IPC.....That a "bottle neck"
> 
> [ if you will ] is created by installing a smaller diameter
> 
> piping......From the angry plumbers in this AHJ, they believe
> 
> that they are compliant by installing the 3/4" pex tubing with
> 
> the insertable type fittings......I would like to know which is
> 
> the compliant installation.
> 
> ** * * **


It would not be a smaller diameter under the code according to 506.4 #13

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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## north star

** * * **

mtlogcabin,

Sorry, wrong code section listed.....Shoulda been Section 504.6, #3,

`06 IPC.

Skip,

So if a plumber installs a 3/4" Watts [ brand ] PEX, 3/4" tubing,

you would approve it as compliant, ...even though they require the

18" separation?

** * * **


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## Glennman CBO

I agree with Skipharper...

3/4" is 3/4".


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## mtlogcabin

06 or 09 it says the exact same thing and #13 would allow pex. If the pex fittings reduced the flow of the pipe they would not meet code

605.5 Fittings.

Pipe fittings shall be approved for installation with the piping material installed and shall conform to the respective pipe standards or one of the standards listed in Table 605.5. All pipe fittings utilized in water supply systems shall also conform to NSF 61. The fittings shall not have ledges, shoulders or reductions capable of retarding or obstructing flow in the piping. Ductile and gray iron pipe fittings shall be cement mortar lined in accordance with AWWA C104.


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## north star

*& & & &*

mtlogcabin,

Respectfully, we may have to agree to disagree!.....The 3/4" [ o.d. ]

pex piping & tubing and the insertable type fittings are smaller than

3/4" [ actual ], and to me, ...this would not meet the intent or letter

of Section 504.6, #3, `06 IPC......Even the 1" pex tubing & piping,

nor the insertable fittings meet the 3/4" i.d. dimension.

I understand that some jurisdictions allow the use of 3/4" pex tubing

& pipe on the t & p valves.

To me, it just does not meet the inside diameters required.

*& & & &*


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