# TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER



## Rider Rick (Feb 2, 2010)

I failed a plumber for a flex line on a T&P relief line off a water heater because the inside diameter was smaller than the inside diameter T&P valve.

The plumber said that the ID of a 3/4" flex line is the same as the ID of the 3/4" CPVC pipe.

I said the code requires the relief valve drain pipe with fittings that will not reduce the interal bore of the pipe and extend from the valve to the outside.

Also I would post on the BB about the ID of 3/4" CPVC pipe for relief valves.

I recieved this e-mail from that plumber today:

Subject:	RE: relief line on water heater

Rick,

I have some information on the T&P relief line off a water heater. On most relief valves there is a

mark stating NPS standing for Nominal Pipe Size, or NPT for Nominal Pipe Tube. On a ¾” relief

valve any listed ¾” pipe will approved for relief lines can be used.  The ID does not matter.

The statement “does not reduce the bore…” refers to a smaller listed pipe (i.e. ½”) or some

non-listed fitting (possibly a water heater flex).

The 2010 UPC Answers & Analysis Committee answered Item #10-01 as follows:

No. Nominal pipe size does not refer to an exact ID or OD of a pipe. It is the

name given to a pipe size and used in the sizing tables in chapter 6 and

appendix A. Industry standards have set the OD’s of different pipe materials

to facilitate the use of fittings and pipe threads etc that work for a number of

pipes. For instance, ¾ copper tube may be used in type K, type L or Type M

pipe. The OD of all three is the same while the ID is different on each. They

are all called ¾ pipe and all use the same fittings to join them.

Considering this issue were Chairman, John J. Roth, City of Houston, TX (Retired); Rex

Crawford, City of Lincoln, NE; Steven Nastruz, Seattle/King County, Seattle, WA; Bruce

Pfeiffer, City of Topeka, KS; Ed Schoenfeld, City of Salt Lake City, UT; G.F. “Jed”

Scheuermann, City of Portland, OR; K. Anthony Wilcockson, City of Walnut Creek, CA

(Retired); Trini Mendoza, County of Ventura, CA and Alfred Ortega, City of Houston, TX.

Thank you for your patience and interest in clarifying this matter.

With this information I will stop using the ¾” nut by nut flex line coming from the relief and

start using ¾” CPVC pipe and fittings to the outside of the house.

This clears up some of the doubt on the ID bore of ¾” CPVC.

Have a good day


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## Pcinspector1 (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Rick,

I had a commercial job that used pex pipe with elbows to get to a discharge drain, I failed it because the elbow fittings were an insert type that reduced the inside of the pex pipe. The plumber changed the line and used external elbows instead I think it was the right call. Once saw a garden hose being used for a T&P line :shock:


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## Mule (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

It's not the size but the rating of the flex connectors. The flex connectors are rated for maximum pressure of 125 PSI and max temperature of 180 degrees. The Temperature Pressure Relief Valve discharges at 150 PSI and/or 210 degrees. Therefore flex lines do not have the rating required to be used for TPR lines.


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## Uncle Bob (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Rick,

First, the UPC committee report is on the use of flex lines used on WATER SUPPLY LINES; not T&P discharge pipe.

If you are using the 2006 IRC; P2803.6.1 Requirements for discharge pipe;

"3.  Not smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap."

There is no reference to nominal pipe size.  The discharge of the T&P valve is a 3/4" female thread.

3/4" CPVC male adapter and pipe has a reduced diameter and does not meet the requirement of # 3.  If the plumber want to use CPVC pipe; he must use an approved 3/4" nipple at the T&P valve and a 1" CPVC female adapter and 1" CPVC pipe.

The purpose of this code requirement is to insure that the diameter of the discharge is not reduced; and the flow is not restricted.

Hope this helps,

Uncle Bob


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## Pcinspector1 (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Please clarify "flex line"


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## Mule (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

This is what I am refering too.


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## Rider Rick (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Thank you to all that replied!  

It is very helpful to me as a building inspector.

Thank you,

Rick


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## Uncle Bob (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

This is from "Watts" who manufacturers T&P valves;

"Drain Lines

A drain line must be connected to the discharge outlet of a T&P relief valve to avoid water damage and scalding injury. A drain line, the same size as the relief valve outlet, must be used in order to channel the discharge of hot water to a safe place of disposal. The drain line must pitch downward to allow for the complete drainage of both the valve and the line. The drain line must never be trapped. Also, the drain line should not contain any shut-off valves, reducing couplings or restrictions.  One must never plug or crimp or reduce the size of a drain line. The T&P valve rating can only be achieved with a full sized discharge line."

See page 6;

http://www.restor.co.za/PDF/Watts_Regul ... manual.pdf

When T&P valves fail; the failure usually starts with a slow leak; which is why it is important for the discharge line to terminate "at a point that is readily observable to the building occupants (2006 IRC, P2803.6.1, number 7.)

The reason for insuring that the discharge pipe and fittings are full size; besides being a requirement of the manufacturer; is because, where the leak is not observed or discovered; deposits from the water heater will build up at the reduction and/or restriction and plug the line; which can result in the water heater exploding.

Hope this helps,

Uncle Bob


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## Rider Rick (Feb 2, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Hello Uncle Bob,

Yes this helps!

Thank you again!

We can always count on you!

Rick


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## mark (Feb 4, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

On the issue of a connector not having the pressure or temperature rating of the t & p valve (connector rating  of 125 psi @ 180 degrees) the temp. rating goes up on the connector when the pressure is lower. The same for pex pipe (check manufactors literature on this). Since the t & p valve is open to the atmosphere the pressure and temp. ratings will allow these products to be used for t & p relief lines.


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## Coug Dad (Mar 24, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Oh Moderators, I think we have problem with this new member


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## Mule (Mar 24, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER



			
				Coug Dad said:
			
		

> Oh Moderators, I think we have problem with this new member


POOF!!! Gone with the wind! Sorry I don't have any authority in the other forums he posted in!


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## skipharper (Mar 24, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Plumbing is always I. D. = inside diameter

a 3/4" copper pipe or a 3/4" pex pipe is 3/4"

The plumber is correct.


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## Rider Rick (Mar 24, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER



			
				skipharper said:
			
		

> Plumbing is always I. D. = inside diametera 3/4" copper pipe or a 3/4" pex pipe is 3/4"
> 
> The plumber is correct.


Watts the manufacturer of the temperature and pressure relief valve requires 3/4" bore from valve to the air gap.

Not all 3/4" pipe has 3/4" ID.

Rick


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## Mule (Mar 24, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

But what is crazy is if you look at the actual opening of a relief valve....what are they....1/4" maybe 3/8"? But they want a full 3/4"?


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## Rider Rick (Mar 24, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Here's my E-mail:

Hi Rick,

Yes , full size 3/4" I.D.

Best,

Ken

Kenneth A Westfall

Technical Support

Watts Water Technologies

815 Chestnut Street

North Andover, MA 01845

978-689-6066  ext. 2154

Fax 978-689-6011

>>> Rick Taylor  3/4/2010 12:56 PM >>>

Hello Ken,

Just to be clear the discharge piping from the relief valve shall be full size  ¾” inside diameter  of non Ferris material.

Thank you,

Rick


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## Glennman CBO (Mar 26, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

If the T&P has a 3/4" female thread (which they do), and you screw a 3/4" male nipple into it, you have already reduced the bore. The only way to not reduce the actual bore of the T&P is to figure out a way to attach the fittings to the outside of the T&P. I agree with the plumber. If the pipe and fittings say 3/4", they are 3/4".


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## Rider Rick (Mar 27, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER



			
				Glennman CBO said:
			
		

> If the T&P has a 3/4" female thread (which they do), and you screw a 3/4" male nipple into it, you have already reduced the bore. The only way to not reduce the actual bore of the T&P is to figure out a way to attach the fittings to the outside of the T&P. I agree with the plumber. If the pipe and fittings say 3/4", they are 3/4".


Glennman,

This is what I like about this BB I don't know all the right answers but I can put the question on this BB and we all can put our heads together and learn together.

The problem here is not all 3/4" plumbing pipe are the same, some are 3/4" on the inside and some are 3/4" on the outside.

When a 3/4" brass nipple is threaded into the 3/4" female thread of the T&P valve the inside bore is a true 3/4" clear hole not ture for the 3/4" CPVC pipe.

Rick


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## Glennman CBO (Mar 29, 2010)

Re: TODAYS PLUMBING QUESTION-RELIEF LINE ON WATER HEATER

Thanks Rick. I love learning things, and brain storming.


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