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Expansion tanks are not needed unless the need for one is needed. Hope you don't need an explanation on that.
No, I do not need an explanation. We are required by local ordinance to install them in the below fashion. The bulk of the homes fed by metered water supply have back flow preventers on them. Therefore several years ago the requirement to install them came forth. However, homes on well systems are not as an expansion tank exist on the system already.

It is not a state code mandate, however the four counties I have been working in do require them. Which is why I asked the question.
 

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On a tankless we can install a valve on the outlet side, since the unit has no storage to expand.
This is gonna make ya wanna scream, tankless's still create expansion.

Some codes require a TXT on them.

I know first hand...had a customer that needed a TXT when the laundry, shower, or toilet shut off the PR would piss.

He had 80psi and wanted to keep the pressure for his shower.
 

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No, I do not need an explanation. We are required by local ordinance to install them in the below fashion. The bulk of the homes fed by metered water supply have back flow preventers on them. Therefore several years ago the requirement to install them came forth. However, homes on well systems are not as an expansion tank exist on the system already.

It is not a state code mandate, however the four counties I have been working in do require them. Which is why I asked the question.
The code says we install them, but it's not enforced.
 

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٩(͡๏̯͡๏)۶&#
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Discussion Starter #26
Orange, Seminole and Polk County require a thermal expansion device on all heating devices.

State code but some municipalities choose not to enforce.

504.4 Relief valve.​
All storage water heaters operating above
atmospheric pressure shall be provided with an approved,
self-closing (levered) pressure relief valve and temperature
relief valve or combination thereof. The relief valve shall conform
to ANSI Z21.22. The relief valve shall not be used as a

means of controlling thermal expansion.

607.3 Thermal expansion control.​
A means of controlling
increased pressure caused by thermal expansion shall be provided
where required in accordance with Sections 607.3.1 and
607.3.2.

607.3.1 Pressure-reducing valve.​
For water service system
sizes up to and including 2 inches (51 mm), a device for controlling
pressure shall be installed where, because of thermal
expansion, the pressure on the downstream side of a
pressure-reducing valve exceeds the pressure-reducing
valve setting.

607.3.2 Backflow prevention device or check valve.​
Where a backflow prevention device, check valve or other
device is installed on a water supply system utilizing storage
water heating equipment such that thermal expansion
causes an increase in pressure, a device for controlling pressure​
shall be installed.
 

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This is gonna make ya wanna scream, tankless's still create expansion.

Some codes require a TXT on them.

I know first hand...had a customer that needed a TXT when the laundry, shower, or toilet shut off the PR would piss.

He had 80psi and wanted to keep the pressure for his shower.
If we install a shutoff on the hot side we have to also install an expansion tank at least twice the capacity of the heaters GPM rating.
 

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Orange, Seminole and Polk County require a thermal expansion device on all heating devices.

State code but some municipalities choose not to enforce.


504.4 Relief valve.
All storage water heaters operating above
atmospheric pressure shall be provided with an approved,
self-closing (levered) pressure relief valve and temperature
relief valve or combination thereof. The relief valve shall conform
to ANSI Z21.22. The relief valve shall not be used as a
means of controlling thermal expansion.

607.3 Thermal expansion control.


A means of controlling
increased pressure caused by thermal expansion shall be provided
where required in accordance with Sections 607.3.1 and
607.3.2.
607.3.1 Pressure-reducing valve.


For water service system
sizes up to and including 2 inches (51 mm), a device for controlling
pressure shall be installed where, because of thermal
expansion, the pressure on the downstream side of a
pressure-reducing valve exceeds the pressure-reducing
valve setting.
607.3.2 Backflow prevention device or check valve.
Where a backflow prevention device, check valve or other
device is installed on a water supply system utilizing storage
water heating equipment such that thermal expansion
causes an increase in pressure, a device for controlling pressure
shall be installed.


I long for the day they create uniform code amongst our counties, unfortunately.... that is most likely a pipe dream.
 

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Wrenchboy
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25 Posts
Oh Lordy,,,,

I hope there is not a sleeping room directly above this service area.

Hell it could be weeping carbon monoxide allready

Do these folks a favor and sell them a proper vent,,,

If they don't accept ,at least a carbon monoxide alarm

This is "an accident waiting to happen"

Dave Doyle
Monrovia,Calif
 

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Always Something
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1,369 Posts
On a tankless we can install a valve on the outlet side, since the unit has no storage to expand.

Well yes and no. By defination, there is no tank, however there is aprox 1/2" gallon of water within the internal piping.

The next generation of tankless heaters will contain a 1 gallong tank, but this will be termed a "mixing" tank. Cool stuff and it actually has a good purpose!!
 

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Always Something
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1,369 Posts
If we install a shutoff on the hot side we have to also install an expansion tank at least twice the capacity of the heaters GPM rating.

Hmmm.... Would it be to protect the closed hot side, or does the Xpan tank need to be incorporated into the tankless? Like the hot shutoff AFTER the tee for the Xpan tank?
 
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