# Thermal Expansion on Rinnai?



## smoldrn (Oct 4, 2010)

Getting ready to start roughing a new restaurant, the City inspector claims that the tankless heater has to have an expansion tank on it.
I'm arguing that the water heater would have to be a tank type in order for there to be an expansion issue. 
Who's right?


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## hroark2112 (Apr 16, 2011)

Is there a storage tank & recirc loop in the system?


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## GREENPLUM (Jul 27, 2008)

Just do what he wants, and you can charge for it!
Who cares if it's needed or not

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## smoldrn (Oct 4, 2010)

No storage tank or circ pump.


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## bdaltonph (Nov 23, 2014)

I have never heard of it myself. I've installed a lot of Rinnias too. All residential though. Have you checked with Rinnias engineers? They may be able to back you up. But sometimes its easier to just give the inspectors what they want


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## A Good Plumber (Jun 18, 2008)

Your inspector apparently doesn't understand that the only time the heater is on is when a faucet is open (that's of course if you don't have a recic pump).

When the faucet is open it's no longer a closed loop and there is no way the residual heat left in the hot water could raise the temperature enough to open the relief valve.


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## The Dane (Feb 19, 2015)

It might only be supposed to heat while water is used but maybe the inspector is afraid of what might happen when it goes bad and won't stop heating. I would just ask him to show me the code that he believes requires it so that I might learn a new thing an if he can't then I might tell him that I cannot make my customer pay all that extra money if it is not actually code. 


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## GAN (Jul 10, 2012)

The only time an expansion tank is needed in any case is if the system is "closed", no backflow protection between the main and the system it is not needed.

Illinois would not differentiate "what" heater is installed, only if the system is closed or not.


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## plbgbiz (Aug 27, 2010)

IPC 2015
*607.3 Thermal Expansion Control.* Where a *storage* water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion tank shall be connected to the water heater cold water supply pipe at a point that is downstream of all check valves, pressure reducing valves, and backflow preventers.

The IPC 2015 Commentary goes on to state regarding tankless on-demand water heaters (gas and electric) that _"...methods for controlling pressure increases due to thermal expansion are not required."_


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## plbgbiz (Aug 27, 2010)

The Dane said:


> It might only be supposed to heat while water is used but maybe the inspector is afraid of what might happen when it goes bad and won't stop heating. I would just ask him to show me the code that he believes requires it so that I might learn a new thing an if he can't then I might tell him that I cannot make my customer pay all that extra money if it is not actually code.


That situation would exceed an expansion tank's capability and is not what they are designed to address. A never ending fire brewing in a closed system is offset by a T&P relief valve.


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## GREENPLUM (Jul 27, 2008)

I was just trying to put some extra cash in his pocket

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## plumberkc (Jun 23, 2011)

My Rinnai RU98i drips from the relief from time to time even after replacing it with a new one. I'm curious if an expansion tank would stop it. I am on an open system so a little confused as to why this happens. 



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## ShtRnsdownhill (Jan 13, 2016)

plumberkc said:


> My Rinnai RU98i drips from the relief from time to time even after replacing it with a new one. I'm curious if an expansion tank would stop it. I am on an open system so a little confused as to why this happens.
> 
> 
> 
> Sent from my iPhone using Tapatalk


experiment and put in an expansion tank, if it stops then it can be brought up to the manufacture, if it keeps dripping, then expansion tank wasnt the issue...either way many problems are solved in the field by playing around and trying different things...nothing lost but some of your time a nd a few bucks in fittings, as you can just plug where the expansion tank went and use it on another job..


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## Sipp (Jul 14, 2016)

plumberkc said:


> My Rinnai RU98i drips from the relief from time to time even after replacing it with a new one. I'm curious if an expansion tank would stop it. I am on an open system so a little confused as to why this happens.
> 
> 
> 
> Sent from my iPhone using Tapatalk


An easier check then to install an expansion tank would be to put a pressure gauge with a tattle-tale needle on the drain, open drain, and give it a few days. If the tattle-tale needle shows that you're getting close to or surpassing 150#, then an expansion tank is the answer. 

I picked up my Watts gauge with tattle-tale for about $11.


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## ShtRnsdownhill (Jan 13, 2016)

Sipp said:


> An easier check then to install an expansion tank would be to put a pressure gauge with a tattle-tale needle on the drain, open drain, and give it a few days. If the tattle-tale needle shows that you're getting close to or surpassing 150#, then an expansion tank is the answer.
> 
> I picked up my Watts gauge with tattle-tale for about $11.


do you have a model # for that guage?


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## Sipp (Jul 14, 2016)

ShtRnsdownhill said:


> do you have a model # for that guage?


I picked mine up at Home Dump, and it's a Watts. Here is one pretty similar, but a bit more pricy.

http://www.homedepot.com/p/Winters-...-and-Range-of-0-160-psi-kPa-PETM213/205962470


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## ShtRnsdownhill (Jan 13, 2016)

Sipp said:


> I picked mine up at Home Dump, and it's a Watts. Here is one pretty similar, but a bit more pricy.
> 
> http://www.homedepot.com/p/Winters-...-and-Range-of-0-160-psi-kPa-PETM213/205962470


thank you, I see they have several at different prices..looks like it can be useful to trouble shoot some issues with water pressures..


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## Sipp (Jul 14, 2016)

Here's a Watt's version.

http://www.ebay.com/itm/like/172318207321?lpid=82&chn=ps&ul_noapp=true


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## Sipp (Jul 14, 2016)

ShtRnsdownhill said:


> thank you, I see they have several at different prices..looks like it can be useful to trouble shoot some issues with water pressures..


It really is helpful. Heck, you need one to properly install a thermal expansion tank. 

When I was at Bradford, I had a plumber call up because the T&P was leaking on a new water heater. He had installed a thermal expansion tank, but the T&P still leaked. So did the next 5!!! T&P's he installed in the water heater! I asked him what the water pressure was in the system. He had no idea. He had assumed that the 40psi precharge on the expansion tank was all that was needed. Once he checked the water pressure (75psi) and properly increased the pressure to the expansion tank, all was good. Fortunately his supply house directed him to the factory prior to him replacing the water heater.


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## ShtRnsdownhill (Jan 13, 2016)

Sipp said:


> It really is helpful. Heck, you need one to properly install a thermal expansion tank.
> 
> When I was at Bradford, I had a plumber call up because the T&P was leaking on a new water heater. He had installed a thermal expansion tank, but the T&P still leaked. So did the next 5!!! T&P's he installed in the water heater! I asked him what the water pressure was in the system. He had no idea. He had assumed that the 40psi precharge on the expansion tank was all that was needed. Once he checked the water pressure (75psi) and properly increased the pressure to the expansion tank, all was good. Fortunately his supply house directed him to the factory prior to him replacing the water heater.


when I set up deep well pumps, the expansion tank has to match what the water pressure is, but there is a gauge on the system already...with the marker this gauge will be more helpful..


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## cmh (Jul 29, 2016)

Sipp said:


> An easier check then to install an expansion tank would be to put a pressure gauge with a tattle-tale needle on the drain, open drain, and give it a few days. If the tattle-tale needle shows that you're getting close to or surpassing 150#, then an expansion tank is the answer.
> 
> I picked up my Watts gauge with tattle-tale for about $11.


A new PRV might be the answer. If pressure exceeds 150 on a tankless water heater without water running, then the incoming pressure is too high to begin with. Unless I'm missing something here


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## Sipp (Jul 14, 2016)

cmh said:


> A new PRV might be the answer. If pressure exceeds 150 on a tankless water heater without water running, then the incoming pressure is too high to begin with. Unless I'm missing something here


You might be correct. But until a gauge is put on the system to see what is going on, it's a guess.


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## MDservices (May 9, 2016)

You need to have an expansion tank because there should be a checkvalve that separates the cold water entry into the tankless... depending the code where you are, but from where I am, especially as soon as you get into commercial, you need that check valve and as soon as there's a check valve, there's potential for expansion, therefore you need one of those mini expansion tanks.


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## MDservices (May 9, 2016)

While the safety valve is there if and when needed, you don't need that going off because usually once it releases pressure, you need to change it often.. they get that tiny constant drip.. very annoying


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## Sipp (Jul 14, 2016)

MDservices said:


> You need to have an expansion tank because there should be a checkvalve that separates the cold water entry into the tankless... depending the code where you are, but from where I am, especially as soon as you get into commercial, you need that check valve and as soon as there's a check valve, there's potential for expansion, therefore you need one of those mini expansion tanks.


While I agree with what you have said when it comes to a tank style water heater, I disagree when it comes to tankless. Since the water HAS to be flowing for a tankless to fire, which means a fixture has to be open, you are no longer in a closed system, so no pressure increase due to thermal expansion.


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## ShtRnsdownhill (Jan 13, 2016)

Ive put in many Takagi tankless and no expansion tanks and no issues...


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## plumberkc (Jun 23, 2011)

Do you have good luck with Takagi? I am looking for something else to install now that Rinnai sold out to Lowes. I was going to install the AO Smith which I believe is made by Takagi. 


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## Debo22 (Feb 15, 2015)

When I install tankless I've been going with Navien lately. Since they have an internal buffer tank do we need to install an expansion tank when a pressure regulator is in the system?


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## ShtRnsdownhill (Jan 13, 2016)

plumberkc said:


> Do you have good luck with Takagi? I am looking for something else to install now that Rinnai sold out to Lowes. I was going to install the AO Smith which I believe is made by Takagi.
> 
> 
> Sent from my iPhone using Tapatalk


yes I have had good luck with them, and the few times I needed to call tech support for a question they were more than willing to help and talk me through a few tests to see what the solution was, the 2 times I had an issue, the dinse switches were in the wrong position from the factory, just a flick of a switch and issue was gone..the oldest one installed is about 15 years old and still going strong, never flushed any out or had any call backs on them...


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## MDservices (May 9, 2016)

Sipp said:


> While I agree with what you have said when it comes to a tank style water heater, I disagree when it comes to tankless. Since the water HAS to be flowing for a tankless to fire, which means a fixture has to be open, you are no longer in a closed system, so no pressure increase due to thermal expansion.


Yeah, I've serviced tankless heaters that don't have expansion tanks nor check valves and different combos, so I know that it can work, but for me on a personal level, I install the mini expansion tank along with check valve, simply put, the codes we have here state that if you have a check valve separating hot side from cold, you need to protect against thermal expansion, so even if the tankless has none, for whatever reason, gotta install that expansion tank. Of course the code states roughly "must protect against thermal expansion where check valve is installed" so you could probably argue that since it's a bit vague but the extra cost/time is really not significant to add the tiny tank. I do it, haven't had a complaint yet.


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## ShtRnsdownhill (Jan 13, 2016)

there is nothing wrong with going above spec, so if one puts in extra parts for peace of mind or just the way they do an install, its not wrong, there are many ways of doing the same thing correct...


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## rwh (Dec 17, 2014)

What about a system with a recirc?


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## BC73RS (Jan 25, 2014)

rwh said:


> What about a system with a recirc?


If the recirc had a pump then yes I would install a check and tank.


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## rwh (Dec 17, 2014)

BC73RS said:


> rwh said:
> 
> 
> > What about a system with a recirc?
> ...


That's what I was wondering.


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## MDservices (May 9, 2016)

I've never installed a recirculating line on tankless hot water heater... wouldn't that defeat the purpose of the tankless? Maybe I'm wrong.. but if you have a recirculating line, your tankless is constantly running.. that's a lot of $$, wouldn't make sense. If you need a recirculating line, you have a client who has a nice home who wants hot water right away or you're in a building that has enough distance from the heater to the faucet in question so you woudn't install a tankless to begin with, you'd install a regular hot water tank or indirect tank or some kind of combination rather than a tankless.

Let me know if I'm wrong here... has anyone ever installed a recirculating line on a tankless water heater??


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## Debo22 (Feb 15, 2015)

MDservices said:


> I've never installed a recirculating line on tankless hot water heater... wouldn't that defeat the purpose of the tankless? Maybe I'm wrong.. but if you have a recirculating line, your tankless is constantly running.. that's a lot of $$, wouldn't make sense. If you need a recirculating line, you have a client who has a nice home who wants hot water right away or you're in a building that has enough distance from the heater to the faucet in question so you woudn't install a tankless to begin with, you'd install a regular hot water tank or indirect tank or some kind of combination rather than a tankless.
> 
> Let me know if I'm wrong here... has anyone ever installed a recirculating line on a tankless water heater??


Yes, Navien A series has a built in recirculating pump.


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## Calrooter (Feb 7, 2017)

Long ago I "disagreed" with the City Inspector. After that, the whole project turn into a nightmare... example? Installation guides and certifications for all material used... Since then, I learned to said...


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## rwh (Dec 17, 2014)

Debo22 said:


> MDservices said:
> 
> 
> > I've never installed a recirculating line on tankless hot water heater... wouldn't that defeat the purpose of the tankless? Maybe I'm wrong.. but if you have a recirculating line, your tankless is constantly running.. that's a lot of $$, wouldn't make sense. If you need a recirculating line, you have a client who has a nice home who wants hot water right away or you're in a building that has enough distance from the heater to the faucet in question so you woudn't install a tankless to begin with, you'd install a regular hot water tank or indirect tank or some kind of combination rather than a tankless.
> ...


Yes, A series does have a recirculating pump. You have to select between internal or external circulation. A hot water return does not defeat the purpose of a tankless heater, it complements it.


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## MECH-MAN (Feb 11, 2017)

The last Rinnai I installed did not require an expansion vessel according to the installation manual. That being said, I installed one anyway. Best not to pick a fight with an inspector about such a small thing. Next time he might ask you to pull those 15 W/C's you just put down to check the flange hight.


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## Tommy plumber (Feb 19, 2010)

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## smoldrn (Oct 4, 2010)

MDservices said:


> I've never installed a recirculating line on tankless hot water heater... wouldn't that defeat the purpose of the tankless? Maybe I'm wrong.. but if you have a recirculating line, your tankless is constantly running.. that's a lot of $$, wouldn't make sense. If you need a recirculating line, you have a client who has a nice home who wants hot water right away or you're in a building that has enough distance from the heater to the faucet in question so you woudn't install a tankless to begin with, you'd install a regular hot water tank or indirect tank or some kind of combination rather than a tankless.
> 
> Let me know if I'm wrong here... has anyone ever installed a recirculating line on a tankless water heater??


Years ago I installed a circ pump on a Rinnai, fed over to a 50 gal storage tank, per Rinnai's engineer. Return line had to be 3/4", worked great.


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## jnohs (Jan 27, 2012)

plbgbiz said:


> IPC 2015
> *607.3 Thermal Expansion Control.* Where a *storage* water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion tank shall be connected to the water heater cold water supply pipe at a point that is downstream of all check valves, pressure reducing valves, and backflow preventers.
> 
> The IPC 2015 Commentary goes on to state regarding tankless on-demand water heaters (gas and electric) that _"...methods for controlling pressure increases due to thermal expansion are not required."_


There is some where else it also stipulates that any vessel used to increase the temperature of water in a closed system has to have an expansion tank. Considering all water heaters are to have a supply shut off valve that if closed creates a closed system until the faucet is opened... So you could comply with the code by installing an expansion tank when ever the faucet is closed and removing it when he faucet is opened........lmaof..... or you could install one and never touch it again, meet code and throw away the whole question if the relief valve is leaking because of no expansion tank...


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## ApolloPlumber (May 2, 2017)

I just installed one in a large custom house yesterday. I noticed the installation drawing showed a expansion tank installed. It was a gas unit with a recirc line, so that must be why. I haven't had to put one in any other unit I have installed in the past.


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## PathMaker (May 10, 2013)

Expansion tanks are NOT designed or used to address the same issue as a T&P. if you read the installation instructions on most expansion tanks (possibly all) they state that the incoming water pressure shall not exceed 80 psi. 

https://s1.img-b.com/faucetdirect.c...flo/992558/proflo-pfxt5i-installation-563.pdf

Pro Flo's cited here,_*The expansion tank should be pre-charged to the incoming system water pressure but must not exceed 80 psi. Failure to properly adjust
the pre-charge will shorten the life expectancy of the product.*_ page 3

Expansion tanks (for water heaters) are designed to reduce the wear and tear caused by the pressure created in a closed loop system on the fixtures installed on that same system. I.e. the dishwasher and wash machine solenoid, the wash machine hoses, toilet fill valves, faucet and valve washers. If the PSI ever gets close to 150 in an expansion tank, the rubber diaphram will either burst, or be pushed so far against the inside of the tank wall as to be useless.

There must be SPACE for the water to expand (thats what creates the pressure build up) inside the tank. 

If the tank is not precharged to match the incoming PSI, (usually set by the prv) than it is NOT going to provide the protection it is supposed to be offering the fixtures and piping in the distribution system. I cant tell you how many plumbers i've seen over the years pull a tank out of the box and plop it right on the threaded connection, without either checking the pre-charge, or the existing system pressure and without matching the two up.

The T&P and the expansion tank serve two totally different purposes.


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