Thread: Expansion Tank on Hot side

I've never seen this before and thought I'd toss this out there... Anyone ever seen an expansion tank installed on the hot side of the water heater? Is there anything inherently wrong with the installation?

Thanks

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Reis,

Where's the Draft Hood?

I'm guessing this installation is in the garage and should be 18 inches above the floor.

Sunday Pot Roast is ready gotta go.

Originally Posted by Reis Pearson

I've never seen this before and thought I'd toss this out there... Anyone ever seen an expansion tank installed on the hot side of the water heater? Is there anything inherently wrong with the installation?

Thanks

Well for starters I'm not aware of any manufacturer that allows for it to be installed on the hot water side. Just a wild guess but I'm betting that a constant supply of hot water on the diaphragm might tend to weaken it. Also the water will want to expand back toward the cool side or the water inlet.

It looks like a Watts tank so you might be able to contact Watts for the correct install guidelines.

This is a direct vent, sealed combustion chamber unit so it does not need to be 18" off the ground as well as it is sealed from the garage. This room used to be part of the garage and they converted to a laundry room with a wall between the garage and the laundry room.

Thanks for the input... I'll check Watts...

Reis,

Sorry no Watts Installation instructions.

This is what I have and it's on the cold side.

Reis:

M1307.3 Elevation of ignition source.
Appliances having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor in garages. For the purpose of this section, rooms or spaces that are not part of the living space of a dwelling unit and that communicate with a private garage through openings shall be considered to be part of the garage.

G2448.2 (624.2) Water heaters utilized for space heating.
Water heaters utilized both to supply potable hot water and provide hot water for space-heating applications shall be listed and labeled for such applications by the manufacturer and shall be installed in accordance with the manufacturer’s installation instructions and this code.

A.O. Smith and State Industries:
INSTALLATIONS IN AREAS WHERE FLAMMABLE LIQUIDS
(VAPORS) ARE LIKELY TO BE PRESENT OR STORED (GARAGES,
STORAGE AND UTILITY AREAS, ETC.): Flammable liquids (such as
gasoline, solvents, propane (LP or butane, etc.) and other substances
(such as adhesives, etc.) emit flammable vapors which can be ignited
by a gas water heater’s pilot light or main burner. The resulting flashback
and fire can cause death or serious burns to anyone in the area. Even
though this water heater is a flammable vapors ignition resistant water
heater and is designed to reduce the chances of flammable vapors
being ignited, gasoline and other flammable substances should never
be stored or used in the same vicinity or area containing a gas water
heater or other open flame or spark producing appliance.

Rheem/Ruud:
This water heater must be installed in accordance with these instructions, local codes, utility company requirements, and/or in the absence of local codes, use the latest edition of the American National Standard/National Fuel Gas Code. A copy can be purchased from either the American Gas Association, 400 N. Capitol Street NW, Washington, DC 20001 as ANSI standard Z223.1 or National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02269 as booklet NFPA 54.

American Water Heater:
IT IS NOT DESIRABLE TO INSTALL A GAS FIRED WATER HEATER IN A
RESIDENTIAL GARAGE. IF INSTALLATION IN A RESIDENTIAL GARAGE IS
YOUR ONLY OPTION, THIS WATER HEATER MUST BE INSTALLED SUCH
THAT THE PILOT FLAME AND MAIN BURNER FLAME ARE NO LESS THAN
18 INCHES ABOVE THE FLOOR (SEE FIGURE 2, PAGE 6). THIS IS TO
REDUCE BUT NOT ELIMINATE THE RISK OF IGNITING FLAMMABLE
VAPORS WHICH MAY BE PRESENT IN A GARAGE. THE WATER HEATER
MUST BE LOCATED OR PROTECTED TO AVOID PHYSICAL DAMAGE BY
VEHICLES OR FLOODING. FAILURE TO FOLLOW THESE WARNINGS
CAN CAUSE A FIRE OR EXPLOSION, RESULTING IN PROPERTY
DAMAGE, PERSONAL INJURY OR DEATH.

Aaron

I'm cool with the sealed combustion chamber relieving the 18" requirement, but there should still be a draft hood. The water heater has to take room air with it to properly draft and without a draft hood, it can't.

Also, I don't like the washing machine hookup that close to the water heater. A washing machine placed there will be too close to the heater itself.

http://www.watts.com/pdf/1915323.pdf

Aaron

Originally Posted by Jon Randolph

I'm cool with the sealed combustion chamber relieving the 18" requirement, but there should still be a draft hood. The water heater has to take room air with it to properly draft and without a draft hood, it can't.

Also, I don't like the washing machine hookup that close to the water heater. A washing machine placed there will be too close to the heater itself.

This is the installation guide for the unit in the picture.

http://www.statewaterheaters.com/lit...183774-000.pdf

It is built without a draft hood..

I had that same State water heater setup on Friday. The "flue" was also a State heater product, so it must come as a "system." I tried to look at the instructions, but the installer put them under the water heater.

On the expansion tank vein, any thoughts on the "adequate drainage" provisions needed for attic installation? This would seem to be a catch 22 when there is no place to install the expansion tank except the attic with the water heater, maybe an alternative valve protection should be used instead of the tank? Any thought from people in the land of no basements?

Originally Posted by Jim Luttrall

On the expansion tank vein, any thoughts on the "adequate drainage" provisions needed for attic installation? This would seem to be a catch 22 when there is no place to install the expansion tank except the attic with the water heater, maybe an alternative valve protection should be used instead of the tank? Any thought from people in the land of no basements?

I have one in my home. The expansion valve has a small tube that takes any water to the exterior of my home. Also the entire unit sits in a drain pan that drains to the exterior and that will catch some of the water if the tank fails

Originally Posted by Scott Patterson

Also the entire unit sits in a drain pan

Scott,

Ever contacted any of the manufacturer's and asked the following two questions (separately on separate occasions, of course).

Question: 'Are your water heater allowed to set down into the drain pan below the top of the drain pan?'

Answer: 'Our water heaters are allowed to be installed with the drain pan as shown in the installation instructions.' (My note: Which, by the way, shows the water heater setting down in the drain pan on the bottom of the drain pan.)

Question: 'The water heater sets in the drain pan below the flood level rim of the drain pan, the drain pan outlet allows approximately 1" of water to remain in the drain pan - are your water heaters allowed to be installed partially submerged like that?'

Answer: 'None of our water heaters are allowed to be partially submerged in water.'

Ever contacted any of the manufacturer's and asked the following two questions (separately on separate occasions, of course).

ECJ:

You'd need to contact their attorneys who write the gibberish that passes as installation instructions. But alas, they aren't allowed to give answers that are partially submerged in the truth.

Aaron

Originally Posted by Aaron Miller

ECJ:

You'd need to contact their attorneys who write the gibberish that passes as installation instructions. But alas, they aren't allowed to give answers that are partially submerged in the truth.

Aaron

Aaron,

No, I did ask those questions, and those are the answers I was given.

I was pointing out that it depends on "how" you ask the question, and that "how" you ask the question will get you different answers ... from the same people.

No attorneys involved, just technical support persons.

One way (as shown in their installation instructions) gets you the 'yes, that is acceptable' when asked if it should be done that way (obviously - they show it that way, so it must be okay).

The other way (when you describe what happens when installed as shown) gets the 'none of our water heaters are designed or approved to be partially submerged' answer.

No attorneys involved, just technical support persons.

Since when is there a company with more that zero employees where no attorney is involved?

Technical support is a known oxymoron.

Doublespeak (dba boolsheit - that's Hannspeak for bullshit) is the official language of business, especially in the USA.

The authors of the IRC don't even being to have a corner on that market, but they are getting more adept by the day at writing nonsense. How prescriptive can a code really be when no on knows what's being prescribed? How instructive can installation instructions actually be when by there mere reformulation of a question, the answer to a simple question differs significantly?

Aaron

Case in point.

Originally Posted by Jon Randolph

I'm cool with the sealed combustion chamber relieving the 18" requirement, but there should still be a draft hood. The water heater has to take room air with it to properly draft and without a draft hood, it can't.

Also, I don't like the washing machine hookup that close to the water heater. A washing machine placed there will be too close to the heater itself.

The whole point of "direct vent" appliances is that they can be used in areas where the typical gas appliance can't be used because they do not obtain their combustion air from the interior but from the exterior. The large curved vent you see has a smaller flue coming through the center of it. Cold air from outside comes in on the outer perimeter of the vent intake and goes to the burner pan to supply combustion air. Exhaust gases rise through the center and exit via the smaller internal vent.

Placing a gas water heater in a laundry room would be a boner move if combustion air were obtained from the interior, because of the corrosive air created by chlorine bleach used to wash laundry, plus, a clothes dryer will affect the amount of combustion air available when the dryer is running - especially if it is a gas dryer - and can actually cause a dryer to backdraft into a house - thus the reason for a sealed combustion direct vent water heater, which is unaffected by the dryer and has no requirement for a draft diverter. In fact, altering this to add a draft diverter would be very dangerous.

ONE TEAM - ONE FIGHT!!!

Mike

The expansion tanks are made for the purpose of absorbing expansion of the hot water when the system is not in use but the water is being heated.
Scenario:
A couple of showers are taken in the morning.
The heater is now mostly cool/cold water. This being more dense.
No longer a demand on the heater and it the regulator has a back check in it (many do) You now have a closed system.
Water expands ~11% as it's heated.
Where does the expanded volume go? Out the TPRV in many cases hence we see them capped off.
Solution: install an expansion tank on the hot side. ( It would actually work on either side since they are both "within the system" so to speak.) Per Watts, the tanks are rated to 150 PSI & 200 degrees.

RE: Direct vent systems
This also comes into play at vent terminations near operable windows etc.
Per the manufacturers, the combustion is controlled due to the engineered co-axial vent systems that do not allow the production of CO so these systems may be vented near windows and since it's a "sealed combustions chamber" there is no ignitions source to consider for the typical garage installation.

This all assumes the systems are correctly installed of course!

Plumber Dude

I don't understand why the installation diagrams show the expansion tanks only on the "cold" side of the system.

These same type of diaphragm tanks are used on radiant heating systems where there is no "cold" side.

Does anyone know if different materials are used for the boiler expansion tanks?

Originally Posted by Michael Larson

I don't understand why the installation diagrams show the expansion tanks only on the "cold" side of the system.

These same type of diaphragm tanks are used on radiant heating systems where there is no "cold" side.

They are the same tanks, however some have larger capacity than others, depending on the size of the closed-loop system. There are specific formulas required to calculate the size of the expansion tank needed for a closed-loop system and a home inspector wouldn't be involved in determining those - only whether what's installed is installed correctly or not.

The rule with an expansion tank in a hydronic heating system is that the circulators in the system must be located so that they pump away from the expansion tank. This allows the differential pressure created by the circulator to be added to the static pressure in the system, reducing the risk of cavitation and expediting air elimination.

Generally speaking, you want the tank to be where it can remain the coolest - even in a closed loop system; otherwise, you end up with uneven water pressures in the system and erratic performance.

ONE TEAM - ONE FIGHT!!!

Mike

Thanks Mike.

Even on hydronic systems I often see the expansion tank on the "heated" side though there is little difference in temp between the supply and return sides the circulating pump is high enough flow. It's usually mounted below a tee fitting with an air trap above it. These temps can easily be above 170 deg. F

My suggestion would be to do as the manufacturers diagrams show. If they show it on the cold water line, then I would say that anything else is wrong because the manufacturer shows it to be only on the cold water side.

Kind of like reverse polarity on an electrical outlet. It will still work, but it is wrong.

Originally Posted by Scott Patterson

Kind of like reverse polarity on an electrical outlet. It will still work, but it is wrong.

Except that there is a very good reason NOT to wire an outlet in reverse.

I just don't see the reasoning for the expansion tank scenario.

Scott;
First of all the paper work for the heater doesn't even show a expansion tank which is correct.
Second, none needed for domestic water.
Know, if it was a Boiler for heating the home, that's a different story?
Can you kindly clarify which it is????

Originally Posted by Leonard Ungar

Second, none needed for domestic water.

Why?


The reason for the expansion tank it so 'take up' water expanding back toward the main water supply (toward the cold water supply of the water heater).

That is where the expansion tank will do the most good back in the direction you do not want the water to go.

The hot water rated expansion tanks are red in color.

Note: The potable water expansion tank shall be installed in the
cold water service pipe line on the supply side of the water heater
(or water storage tank).

From the Watts site
Also, take a look at the design on this model of inline unit. I have never seen this one before.

http://www.watts.com/pdf/es-ilt.pdf

Originally Posted by Michael Larson

Except that there is a very good reason NOT to wire an outlet in reverse.

I just don't see the reasoning for the expansion tank scenario.

The analogy is to show that it can be wrong and still work or give the perception that it is working properly when in fact it is not.
I used electricity because you can wire/connect all types of things wrong and they will still work.

Originally Posted by Jim Luttrall

From the Watts site
Also, take a look at the design on this model of inline unit. I have never seen this one before.

http://www.watts.com/pdf/es-ilt.pdf

Jim gets the Cupie doll!

#1 One way check valve on inlet side required where i live.
#2 TPR should take care of the expansion.
#3 No harm done if you do put a tank in on the cold side.
#4 Did you notice the plastic drain line from the TPR valve, not good ????

Originally Posted by Leonard Ungar

Scott;
First of all the paper work for the heater doesn't even show a expansion tank which is correct.

You are correct that the one I posted does not, but this is for the water heater and not an expansion tank. Watts has it on their site for the expansion tank.

Second, none needed for domestic water.
Know, if it was a Boiler for heating the home, that's a different story?

Well I'm not quite sure about this. Can you post anything that covers this.

Can you kindly clarify which it is????

I think it has been done.

Originally Posted by Leonard Ungar

#1 One way check valve on inlet side required where i live.

This is common in many areas.

#2 TPR should take care of the expansion.

That is not what a TPR is for. With a constant drip of a TPR it could allow mineral deposits to build up and freeze the valve so it will not work when needed. I think Watts has a good description on their site about this.

#3 No harm done if you do put a tank in on the cold side.

Watts says different.

#4 Did you notice the plastic drain line from the TPR valve, not good ????

CPVC is OK for a TPR line.

Originally Posted by Jim Luttrall

From the Watts site
Also, take a look at the design on this model of inline unit. I have never seen this one before.

http://www.watts.com/pdf/es-ilt.pdf

Yeah But Do They Make A Red One?

The purpose of an expansion tank is to protect the water heater & plumbing from high water pressure.

The T&P valve is an Emergency Relief Valve and is not intended to correct High Water pressure coming in from the main.

This may have been posted already, but to clarify the need for thermal expansion protection, here it is again. IRC 2003
First off though, if maximum static water supply pressure exceeds 80 PSI, you have to have an approved pressure reducing valve. P2903.3.1

Then
P2903.4 Thermal Expansion. In addition to the required pressure relief valve, an approved device for thermal expansion control shall be installed on any water supply system utilizing storage water heating equipment whenever the building supply pressure exceeds the pressure reducing valve setting or when any device, such as a pressure reducing valve, back flow preventer or check valve, is installed that prevents pressure relief through the building supply. The thermal expansion control device shall be sized in accordance with the manufacturer's installation instructions.


The TPR valve is not suffiecient for thermal expansion.

Yeah But Do They Make A Red One?

Yep!

Series DETA ASME Potable Water Expansion Tanks are used on commercial and industrial potable hot water applications to absorb the increased volume of water created by thermal expansion.

It is a red one!

Originally Posted by Jim Luttrall

Yep!

It is a red one!

Great,

Then they are made to be Installed on the Hot side and the Manufacturers Installation Instructions will sate that.

So the Manufactures install instructions will tell you which side the product should go.

OK, the expansion tank issue has been explored. You did call out the copper lines in contact with the Uni-Strut right? (The channel shaped steel brackets attached to the wall). While this stuff works great for attaching conduit and steel piping to walls, it just ain't good on copper.
Alton

CPVC is OK for a TPR line.

Scott:

Yes and no. 3/4" CPVC is undersized at less than .75" interior diameter - not allowed. 1" CPVC is OK, with no more that 4 bends between valve and terminus.

Aaron

Originally Posted by Leonard Ungar

#2 TPR should take care of the expansion.

The T&P relief valve will not only work "properly" as a thermal expansion relief valve, I would not even state that it would work "improperly" for that use as it is not designed for, nor intended for, that use.

#3 No harm done if you do put a tank in on the cold side.

There is when the manufacturer states to install it on the cold water supply piping.

Originally Posted by Alton Darty

You did call out the copper lines in contact with the Uni-Strut right? (The channel shaped steel brackets attached to the wall). While this stuff works great for attaching conduit and steel piping to walls, it just ain't good on copper.
Alton

Every time dissimilar metals touch each other - yes.

Originally Posted by Aaron Miller

Scott:

Yes and no. 3/4" CPVC is undersized at less than .75" interior diameter - not allowed. 1" CPVC is OK, with no more that 4 bends between valve and terminus.

Aaron

Yes and no and yes.

'Reduced in size' refers to 'nominal trade size', and 3/4" CPVC is still '3/4" nominal trade size'. Means you cannot reduce it to 1/2" or smaller.

Thus, yes, 3/4" CPVC is allowed for use as the discharge line from a 3/4" T&P valve.

Bush Coast Jerry:

From Watt's Literature:

WARNING

: To avoid water damage or scalding due to valve operation, discharge line must be connected to valve outlet and run to a safe place of disposal. Discharge line must be as short as possible and be the same size as the valve discharge connection throughout its entire length.
Discharge line must pitch downward from the valve and terminate at least 6" (152mm) above a drain where any discharge will be clearly visible. The discharge line shall terminate plain, not threaded. Discharge line material must conform to local plumbing codes or ASME requirements. Excessive length over 30' (9.14m), or use of more than four elbows or reducing discharge line size will cause a restriction and reduce the discharge capacity of the valve.

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 be threaded and such discharge pipe shall not have a valve installed.

http://www.texasinspector.com/Flogua...n%20Manual.pdf

Note that the ID of the 3/4" piping is .715" and not .75" as in the case of 3/4" copper.

http://www.texasinspector.com/T&P%20...ash%20Acme.pdf

In case the valve is Cash Acme instead of Watts.

Please support your argument,

Aaron

Originally Posted by Aaron Miller

Excessive length over 30' (9.14m), or use of more than four elbows or reducing discharge line size will cause a restriction and reduce the discharge capacity of the valve.

Yep, I was writing that up 15 years ago.

P2803.6.1 Requirements of discharge pipe.

The diameter of the discharge piping shall not be less than the diameter of the relief valve outlet.

Texas Heat Stroked Aaron,

What is the "diameter of the relief valve outlet"?

Why, it is " 3/4 inch nominal trade size " .

If you want to get into applying fractions of an inch, start here:

Take the relief valve and look at the threaded discharge opening ...

Now, consider this: "Can you thread in *ANY* adapter fitting into that threaded opening *WITHOUT REDUCING* that opening?"

Nope. NO WAY JOSE!

So, we are back to " 3/4 inch nominal trade size ".

So, we are back to " 3/4 inch nominal trade size.

BCJ:

And that, you see is the right answer, but just not to this question. It belongs to this question:

I would need to know the size according to the rifle to be supplied.

Now, you're on the right track . . .

Aaron

THSA,

I see you did not come up with a different answer to:

Originally Posted by Jerry Peck

Take the relief valve and look at the threaded discharge opening ...

Now, consider this: "Can you thread in *ANY* adapter fitting into that threaded opening *WITHOUT REDUCING* that opening?"

Nope. NO WAY JOSE!

So, we are back to " 3/4 inch nominal trade size ".

Guess you are seeing the light and the reasoning? You?

Let me throw this in for discussion.

If there is no backflo preventer in the system supply line what is an expansion tank doing?

Guess you are seeing the light and the reasoning?

BCJ:

Maybe, but it's more complicated than you make it sound:

Pipe was originally sized based on the inside diameter of the pipe that was typical of the period, which was cast iron. A half inch cast iron pipe was exactly one half inch inside diameter. The thickness of its wall determined the outside diameter. In order to insure that all pipes and fittings would go together, the standard was established based on that specific outside diameter.

Today, that size remains the standard by which pipe is measured, but since materials have changed, wall thicknesses of pipe, and therefore the inside diameters vary. Consequently, a half inch pipe is neither a half inch on the inside nor the outside, but it is still called a half inch pipe based on the Nominal size established by Iron Pipe of yesteryear. Hence the terms NPS for "Nominal Pipe Size" or IPS (Iron Pipe Size). The terms are interchangeable.

Pipe is distinguished from tubing by the standard by which it is measured. Pipe is thick walled, and in standard IPS sizes. When copper tubing was developed, the walls were much thinner than cast iron or steel. Because of copper's unique characteristics, it was deemed not necessary that it be made in IPS sizes. A new standard was developed called CTS or "Copper Tube Size" that was much smaller. The actual size of CTS is much closer to its nominal size than that of pipe.

The standard has evolved so that any product made in IPS sizes is called pipe and any product made in CTS sizes is called tubing, without regard to any differences in material or manufacturing process. CPVC is an exception, being called "pipe" but being sold in CTS.

Pipe is available in a number of different thicknesses or "schedules." The American Society for Testing Materials (ASTM) establishes the standards by which they are graded. The ASTM has assigned standards to each schedule of pipe made, and those standards dictate their use.

Pipe size is determined by its inside diameter (ID). Its outside diameter (OD) will vary with the thickness of its walls.

Three different weights designations are used for pipe: Standard wall (Std.), extra strong wall (XS) and double extra strong wall (XXS). These last two designations are sometimes referred to as extra heavy wall (XH) and double extra heavy wall (XXH), respectively.

So then, which is CPVC in your opinion, pipe or tubing? It is made in CST (tubing) sizes but is wrongly labled by "plumbers" as pipe. If, as it seems certain to me and should be blatantly obvious to you as well, it is tubing, the nominal pipe zie won't do.

I know, it's like I'm totally ignoring the fact that you said "nominal trade size". That terms means nothing to me. Maybe that's what you told your first girlfriend when she asked about the dimensions of the dangler. Truth in advertizing?

Aaron

If there is no backflo preventer in the system supply line what is an expansion tank doing?

Allowing a space for thermal expansion.

Originally Posted by Aaron Miller

Allowing a space for thermal expansion.

Really?

Without a backcheck/backflo device I would think it would just end up back in the main unless the expansion tank pressure was set lower than the main.

Bladder tanks are required in a closed loop water heating system to absorb the expanding fluid and limit the pressure within a heating or cooling system. A properly sized expansion or compression tank will accommodate the expansion of the system fluid during the heating cycle without allowing the system to exceed the critical pressure limits of the system. The expansion or compression tank uses compressed air to maintain system pressures by accepting and expelling the changing volume of water as it heats and cools. Some tank designs incorporate a diaphragm or bladder to isolate the expanded water from the pressure controlling air cushion. As water is expanded, it is contained in the bladder preventing tank corrosion and water logging potentials. The pressure controlling air cushion is pre-charged at the factory and can be adjusted in the field to meet critical system requirements.

I know what they are and how they work.

I'm questioning the need if there is no backflo preventer on the street/supply line.

Thermal expansion tanks are not required by the IRC unless it is a closed system. If pressure can go back to the city main, no need for a tank.

One note though, some water meters are now being used that have an integral check valve which would mean the system would be closed.

P2903.4 Thermal Expansion. In addition to the required pressure relief valve, an approved device for thermal expansion control shall be installed on any water supply system utilizing storage water heating equipment whenever the building supply pressure exceeds the pressure reducing valve setting or when any device, such as a pressure reducing valve, back flow preventer or check valve, is installed that prevents pressure relief through the building supply. The thermal expansion control device shall be sized in accordance with the manufacturer's installation instructions.

Originally Posted by Jim Luttrall

One note though, some water meters are now being used that have an integral check valve which would mean the system would be closed.

That's good info Jim. I wasn't aware of that.
How can you tell the difference?

I have tried quickly to find a photo on-line, but failed. I had just read about them appearing in the field, and about a month ago found a new one installed in a smaller community near me. It looked like a traditional underground meter with a check valve grafted onto the end. I would not have noticed the difference except that it was shiny and clean having been swapped out while I was inside the house. I will check my photo files later to see if I can find a decent picture. The previous discussion was either here or at TIJ.

Originally Posted by Aaron Miller

I know, it's like I'm totally ignoring the fact that you said "nominal trade size". That terms means nothing to me.

Nominal trade size is used interchangeably with IPS and NPS, and, when you use fittings (male and female adapters) for copper tube, those adapters are sized in IPS / NPS / nominal trade size.

So there is no need to fret about CPVC being "pipe" and being sized to CTS (copper tube size) as the adapters for copper tube are listed in IPS / NPS ... i.e., 'nominal trade size'.

3/8"
1/2"
3/4"
1"
etc.

Thus, the threaded discharge opening of the T&P relief valve is 3/4" IPS / NPS / nominal trade size and into which is intended to be screwed in a pipe or adapter of the appropriate size.

Screwing in *ANY* pipe or adapter *WILL REDUCE THE SIZE* of that opening, even if you were to screw in a 3/4" IPS / NPS / nominal trade size male adapter for use with a 3/4" CTS pipe.

REGARDLESS ... you have "reduced the size of the opening" from its actual measured dimension - so much for your fractional measurements, you *HAVE NOT* reduced the opening size in nominal trade size (i.e., IPS / NPS).

That said, screwing in an adapter for for 3/4" CTS copper, or 3/4" CTS CPVC ... wait, aren't they both in CTS?

Yep, they sure are. neither is any different than screwing in an IPS galvanized pipe - all are 3/4" nominal size and all reduce the discharge opening size approximately the same amount.

So the argument is over 0.035"? Sorry, but if the code and manufacturer don't make a big deal out of it, 35 thousandths of an inch is not going to make it on my radar screen. Nominal dimensions are pretty much the standard in what I have seen through-out the code. A 2x4 is not 2.000 inches by 4.000 inches. I think the spirit of the code is pretty clear that you don't intentionally make the pipe smaller than the discharge of the TPR valve.
There are bigger fish to fry.

There are bigger fish to fry.

Oh, really? You don't have a dog in this fight. Take this, sit in the corner and and read up on those big fish things while we finish this discussion . . .

Aaron

One might wonder why such an even tempered well adjusted fellow would have such light reading material at the ready, not ME, mind you, but someone might.

Originally Posted by Leonard Ungar

Scott;
First of all the paper work for the heater doesn't even show a expansion tank which is correct.
Second, none needed for domestic water.
Know, if it was a Boiler for heating the home, that's a different story?
Can you kindly clarify which it is????

This is a domestic water heater. In these parts some jurisdictions require expansion tanks as well as TPRV. As far as I'm aware the drain tube can be...
1. Be constructed of an approved material such as CPVC, copper, polyethylene, galvanized steel, polybutylene, polypropylene, or stainless steel.
2. Not be smaller than the diameter of the outlet of the valve it serves (usually no smaller than 3/4").
This is a CPVC and Galvanized 3/4" line.

Nominal trade size is . . . to be screwed . . .
Screwing in . . . that opening, even if you were to screw in a 3/4" IPS / NPS / nominal trade size male adapter for use with a 3/4" CTS pipe ... you have "reduced the size of the opening" . . . That said, screwing . . . Yep, they sure are . . . different than screwing in . . . the discharge opening size approximately the same amount.

Typical Bush Coast speech.

Aaron

For those of us in Illinois (underlining is mine):

ILLINOIS PLUMBING CODE 890.1130 (g)(7) Closed water systems shall have a properly sized thermal expansion tank located in the cold water supply as near to the water heater as possible and with no shut-off valve or other device between the heater and the expansion tank. Exception: In existing buildings with a closed water system, a properly sized pressure relief valve may be substituted in place of a thermal expansion tank. For closed water systems created by backflow protection in manufactured housing, as required in Section 890.1140(i), a ballcock with a relief valve may be substituted for the thermal expansion tank.

Section 890

Michael,
Many pressure regulators out here have built-in back checks and thus create a closed system. When I've had problems with a system pissing out the TPRV all the time, an
expansion tank handles it.
Dana

Originally Posted by Fritz Kelly

Sounds like it is OK to me.

Fritz,

That label says it is not suitable for use on the hot side.

Fritz,

Watts PLT-5

Look Here------ http://www.watts.com/pdf/IS-PLT.pdf

Fritz,

It says it on the label here: (underlining is mine)

"This Expansion Tank is designed and intended for storage at a maximum pressure of 150 pounds per square inch gauge (150 psig) and a maximum temperature of 200 degrees F." (except I don't have the "degree" symbol)

T&P safety relief valves are set at a maximum pressure of 150 psi, so that would meet the pressure requirement, they are also set at a maximum temperature of 210 degrees F, which exceeds the maximum 200 degrees F allowed.

Thus, it is not allowed on 'the hot side', which could be 150 psi or 210 degrees F, they can, however, be installed on the cold side, which will not get that hot until after the hot side has, in which case the T&P would have (should have) popped open, lowering the temperature on the hot side.