Expansion Tank Question

[Robert Foster]

I've got some questions about expansion tanks.

I've had probably six houses in the last few weeks which had municipal water supplies and no expansion tanks. These houses all had at least one leaking plumbing fixture. The type of leak when you turn on the fixture and water comes out where it's not supposed to. Are faucet washers, teflon tape etc. the weak link in the water distribution system that let go first when there is no expansion tank installed or are these observations unrelated ? I'd think they'd be unrelated since those components are generally downstream of the valves when the valves are closed...but the recent frequency of finding both started me wondering.

Are the water distribution systems in most houses on municipal water supply considered closed systems...meaning there is some pressure reducing valve, backflow preventer or metering device at the municipal connection that prevent backflow, confining water heating induced pressure fluctuations in the house distribution system?

Alternatives to expansion tanks. In my travels around this site I think I've read about two alternative ways to provide expansion means to a closed system with water heating capability. One is a device installed in toilet tanks and another is a pressure release valve (similar to a TPRV on the water heater but having a lower set point) that discharges to the exterior of the home. What are the accurate names of these two devices and are they in general use? I'd like to learn more about them.

Thanks.

[Steven Turetsky]

You seem to be going to great lenghts to avoid expansion tanks, why?

When you have a heat system, in addtion to TPRV, and pressure reducer valve, you also need an expansion tank. The expansion tanks helps the heating system maintain the proper pressure.

[Jim Luttrall]

Steven, I think you misread the OP and his intent. He wants to learn about the other approved methods of thermal expansion devices for general knowledge. Remember we don't get to chose what we inspect, better to be informed about all possibilities, not just the ones we like.;)

[Robert Foster]

Absolutely...thank you Jim. I'm not trying to avoid anything except ignorance.

I enjoy learning more than just the minimum needed to inspect, just saying the item is broken or missing...repair and replace...doesn't cut it for me...I'd be bored in no time. I like to explain what the problem is, why it is a problem for the house or the occupants and then call for it to be corrected. I believe that serves my clients better by presenting them with more information to bargain more effectively with. It also contributes to me never having had a call back yet from a client, agent or the professional doing the correcting calling me out or asking for greater explaination. The greater depth of knowledge I have the better I can articulate the second part of my comments.

Steven....my impression from reading your posts around here is you operate the same way. I assume your misread of my original post was a combination of my mediocre writing skills and your probably being busy. :)

[Scott Patterson]

I have always called them expansion relief valves.

[H.G. Watson, Sr.]

You have asked about a number of different things.Pressure relief and pressure regulators are not exactly the same thing.

Pressure regulation and relief can be regarding a multitude of different things.

Temperature variations and thermal expansion are one of several contributory factors which can lead to operating pressure variences in a plumbing system, but the problem of thermal expansion is more than simple pressure relief - there has to be a means to deal with the increased (expanded) volume of liquid water.

Thermal expansion bladder tanks operate differently then for example a Watts brand Governor, which is a thermal expansion relief valve in combo with a ball cock which actually discharges the excess water into the toilet tank. Pressure regulators, booster pumps, pressure tanks, have different purposes. Regarding overall incoming pressure regulators/reducers, generally employed at the service just after the meter, and usually to step down in general or moderate peaks in pressure incomming to protect the local plumbing system. These pressure regulators may be bypass-type or closed type in their effect on the local (downstream) plumbing system (ability to off put or adjust for) by-pass thermal expansion back to the utility distribution system).There are other type relief valves, check valves, and back flow preventors for different purposes.

IIRC Ron Hasil has posted several times rather comprehensively on the various types, how they work, and their relief or discharges and how they are tested, calibrated, and recertified. You might check some of his posts in the plumbing area. (For example Atmospheric Vacuum Breakers, Double Check Valves [DCVs], Reduced Pressure Zone [RPZ] backflow preventors; etc.)

I think some searches here will bring up some discussions on pressure regulators, pressure tanks, expansion tanks, and the Watts (brand) Governor products also. Many discussions in the past are peppered with links to materials and general information on the various subjects you've brought up in your OP.

You are correct that the weakest points dripping, or leaks such as mixing valves in single handled faucets, seats and cartridges, sprayer/diverters, and float valves, can be a symptom of too-high system pressure of a plumbing system causing these parts to fail early. Thermal expansion can be a cause. Also continuous un-relieved (un opened valves/no running water) non-stop heating of water can cause a hydrogen gas build-up in the plumbing system, contributing not only to pressure but a potentially dangerous/deadly/flamable/explosive condition for which a TPRV and expansion tanks offer no protection or remediation for.

[Robert Foster]

Thank you Scott & HG. The Watts toilet tank Governor 80 / thermal expansion relief valve. Governor 80 Ball Cock and Thermal Expansion Relief Valve, Relief Valves/Ball Valves, Water Safety & Flow Control - Watts (http://www.watts.com/pages/_products_details.asp?pid=855)

I had a little time this morning and a visit to the posts by Ron Hasil turned up a lot of information for me to digest. As far as I can tell so far the existence of both bypass or closed type pressure regulators is the sticky wicket from an inspection stand point.

My brief reading so far leads me to believe while the bypass pressure regulators exist they are not typically found in a majority of residences, and where they are inspectors and plumbers still prefer (not sure, maybe required) an expansion tank be installed as well. I need to read some more on this and ask around my local area...

[Steven Turetsky]

Steven, I think you misread the OP and his intent. He wants to learn about the other approved methods of thermal expansion devices for general knowledge. Remember we don't get to chose what we inspect, better to be informed about all possibilities, not just the ones we like.;)

Robert and Jim,

Perhaps I did read something else into the original post, and I look forward to the responses as I hope to learn something new too.

I don't recall ever coming across an expansion relief valve that can replace an expansion tank (perhaps it's a regional thing, or perhaps it too new or rare).

Now a relief valve at the toilet sounds like a good thing, especially if there is fluctuating high water pressure at the municipal supply. I don't understand how it will assist the heating system, since there is a big difference in the average pressure of the water supply and pressure within the heating system.

[Jim Luttrall]

Robert and Jim,

Perhaps I did read something else into the original post, and I look forward to the responses as I hope to learn something new too.

I don't recall ever coming across an expansion relief valve that can replace an expansion tank (perhaps it's a regional thing, or perhaps it too new or rare).

Now a relief valve at the toilet sounds like a good thing, especially if there is fluctuating high water pressure at the municipal supply. I don't understand how it will assist the heating system, since there is a big difference in the average pressure of the water supply and pressure within the heating system.
Ah ha, there is the missing tidbit, he is talking about water distribution systems, not heating systems. The water heater on the potable water supply will only need an expansion device IF the system is closed as would be the case if there is a conventional pressure regulator valve between the W/H and the municipal supply.

Watts has a few different devices for the purpose. See half way down the page at the "Watts Potable water solutions" heading.
Thermal Expansion - Learn About - Watts (http://www.watts.com/pages/learnAbout/thermalExpansion.asp?catId=64)

[Tom Thompson]

When ever a water pressure regulator is installed that doesn't contain a integral bypass and/ or if the city water pressure exceeds the rating of the TPR valve (normally 150 PSI), expansion tanks are required. They absorb the pressure and or expansion of the water as it's heated with a rubber air separation or bladder in the tank that is set to pressure of normally 125 PSI. If the system was closed or excessive pressure exists, the TPR valves might leak or blow off.
I fergot to mention when expansion tanks are used, check valves on (cold) inlet are required, making the hot system closed. TPR are also reuqired. This allows expansion tanks to absorbe expansion properly.

[Robert Foster]

Did some more reading last night...and as usual answered some questions while creating a couple more. The Watts pressure reducing valves with the optional bypass feature only open the bypass when the domestic pressure becomes greater than the municipal pressure.

So with municipal systems having supply pressures greater than 80 psi, whether the home's PRV has a bypass feature or not is a mute point for inspection purposes...the home still needs an expansion tank to fine tune the systems pressure regulation and protect the plumbing components from pressure spikes.

Question is how to determine the municipal supply pressure at the particular house being inspected and is that necessary. Here in my small mountain town that pressure is over 100 psi. Obviously the pressure probably varies a lot from one town/city to another but there are probably some regional averages you can use as a yard stick.

Is knowing the municipal supply pressure even necessary ? Things being as they are municipal supplies are surely prone to fluctuations and spikes so having a expansion tank in addition to the PRV with bypass feature is probably a wise idea.

[Jim Luttrall]

Again, a tank is not the only acceptable means of protecting the system from excess pressure. I try to use thermal expansion protection "device". If I see a pressure regulator or know that there is one present due to the neighborhoods municipal pressure, I call out the lack of a thermal expansion device. As you noted, pressure can only be relieved if the municipal pressure is lower than the house pressure, making an integral bypass feature a moot point when high municipal pressures exist. My city has a pressure gradient map available which is helpful in getting a ball park idea of city pressure.

[Benjamin Thompson]

When ever a water pressure regulator is installed that doesn't contain a integral bypass and/ or if the city water pressure exceeds the rating of the TPR valve (normally 150 degrees), expansion tanks are required. They absorb the pressure and or expansion of the water as it's heated with a rubber air separation or bladder in the tank that is set to pressure of normally 125 PSI. If the system was closed or excessive pressure exists, the TPR valves might leak or blow off.

Good post in that it also shows that in most homes an expansion tank really isn't needed.

[Jim Luttrall]

Good post in that it also shows that in most homes an expansion tank really isn't needed.
Not really, anytime the water pressure is over 80 PSI a pressure regulator is needed and when a pressure regulator is required, some sort of thermal expansion protection is needed. In my area, probably upwards of 75% of the homes need a pressure regulator and thus a thermal expansion tank or other device.
I'm not sure why the other pressures mentioned enter the picture.

[Garry Sorrells]

Robert,
In your OP you stated..."..had municipal water supplies and no expansion tanks. These houses all had at least one leaking plumbing fixture.".....

I may have missed a reply directed at this, if sorry. But, is part of your inquiry a correlation between leaking plumbing fixtures and expansion tanks not being present ?

Is it possible that the correlation is to age of the property and use of fixture that may be creating a higher instance of leaking fixture. Older homes did not have expansion tanks installed when first built. H2O heater then replaced and expansion tank installed. While plumber is there fixture leaks are repaired. Could it just be a age maintenance correlation that you are seeing?

[Ted Menelly]

I am all over DFW and I cannot remember one time where the pressure exceeded slightly over 75 lbs. Usually the case is 60 to 70 lbs. In several neighborhoods I find the pressure in the 50s.

[Robert Foster]

Robert,
Is it possible that the correlation is to age of the property and use of fixture that may be creating a higher instance of leaking fixture. Older homes did not have expansion tanks installed when first built. H2O heater then replaced and expansion tank installed. While plumber is there fixture leaks are repaired. Could it just be a age maintenance correlation that you are seeing?

Absolutely Gary. In such a short time I ran into so many leaking fixtures with no expansion tanks it got me thinking. With all the variables it would be impossible to link the two except for maybe that poor work practices are contagious throughout a given system. At least half of my inspections are usually on private wells so the string of municipal inspections was also something of an anomaly for me.


Again, a tank is not the only acceptable means of protecting the system from excess pressure. I try to use thermal expansion protection "device". If I see a pressure regulator or know that there is one present due to the neighborhoods municipal pressure, I call out the lack of a thermal expansion device. As you noted, pressure can only be relieved if the municipal pressure is lower than the house pressure, making an integral bypass feature a moot point when high municipal pressures exist. My city has a pressure gradient map available which is helpful in getting a ball park idea of city pressure.

Yea thanks again Jim....my comment states something along the lines..."the thermal expansion device is typically an expansion tank". A pressure gradient map....think I could get the 20+ towns, counties and cities I do work in to provide me one of those.:D

[Scott Patterson]

I am all over DFW and I cannot remember one time where the pressure exceeded slightly over 75 lbs. Usually the case is 60 to 70 lbs. In several neighborhoods I find the pressure in the 50s.

That's cuz everything in your area is flat and the pressure is dependent on pumps! Heck in my neck of the hills, our water tanks are on hilltops and gravity takes over when it comes to pressure. Without a PRV we will see water in the 100psi to 150+psi range!

My home according to my GPS sits at 1050' and a water tank that I think my water comes from is good 500' above me on a hilltop.

[Robert Foster]

That's cuz everything in your area is flat and the pressure is dependent on pumps! Heck in my neck of the hills, our water tanks are on hilltops and gravity takes over when it comes to pressure. Without a PRV we will see water in the 100psi to 150+psi range!

My home according to my GPS sits at 1050' and a water tank that I think my water comes from is good 500' above me on a hilltop.

Same here....flatlanders what do they know about water pressure. :D

In case the smilie doesn't make it clear ...the above is a joke meant for entertainment purposes ...I'd love to visit the fine State of Texas some day on my motorcycle...

[James Duffin]

That's cuz everything in your area is flat and the pressure is dependent on pumps! Heck in my neck of the hills, our water tanks are on hilltops and gravity takes over when it comes to pressure. Without a PRV we will see water in the 100psi to 150+psi range!

My home according to my GPS sits at 1050' and a water tank that I think my water comes from is good 500' above me on a hilltop.

A water tank 500' high would give you about 216 pounds of pressure. That is a lot of pressure and puts a strain on some older water lines.

[R.A .McBride]

Same here....flatlanders what do they know about water pressure. :D

In case the smilie doesn't make it clear ...the above is a joke meant for entertainment purposes ...I'd love to visit the fine State of Texas some day on my motorcycle...
Why come down here it,s just boring and flat!:) Actually I am in an area close to ted and we do have pumped water systems ,but we also have areas in my town that have excessive pressure ,over 150 psi. Average is around 75 to 120. we do require PRV,s and a means for thermal expansion as long as it is an approved means. Anything over 80 psi has to be regulated.

[Tom Thompson]

Did some more reading last night...and as usual answered some questions while creating a couple more. The Watts pressure reducing valves with the optional bypass feature only open the bypass when the domestic pressure becomes greater than the municipal pressure.

So with municipal systems having supply pressures greater than 80 psi, whether the home's PRV has a bypass feature or not is a mute point for inspection purposes...the home still needs an expansion tank to fine tune the systems pressure regulation and protect the plumbing components from pressure spikes. "not a mute point, pressure for over ran heater can push backwards into city system that don't exceed 150 PSI, expansion tank won't help fine tune, city pressure spikes don't pass through regulators, no effect on house"

Question is how to determine the municipal supply pressure at the particular house being inspected and is that necessary. Here in my small mountain town that pressure is over 100 psi. Obviously the pressure probably varies a lot from one town/city to another but there are probably some regional averages you can use as a yard stick. " Water supplier can give you high and low pressures"

Is knowing the municipal supply pressure even necessary ? Things being as they are municipal supplies are surely prone to fluctuations and spikes so having a expansion tank in addition to the PRV with bypass feature is probably a wise idea." "regulator bypass won't help if city pressure exceeds TPR ratings, see my post above for more info"

[Tom Thompson]

Ah ha, there is the missing tidbit, he is talking about water distribution systems, not heating systems. The water heater on the potable water supply will only need an expansion device IF the system is closed as would be the case if there is a conventional pressure regulator valve between the W/H and the municipal supply.

Watts has a few different devices for the purpose. See half way down the page at the "Watts Potable water solutions" heading.
Thermal Expansion - Learn About - Watts (http://www.watts.com/pages/learnAbout/thermalExpansion.asp?catId=64)
Jim; Expansion tank installations require check valves on the inlet side (cold) to water heaters, making the hot system closed. TPR valves are also required.

[Jim Luttrall]

[Yea thanks again Jim....my comment states something along the lines..."the thermal expansion device is typically an expansion tank". A pressure gradient map....think I could get the 20+ towns, counties and cities I do work in to provide me one of those.:D[/quote]
Last time I checked, my city had it on-line. Worth checking it out, very interesting.
Most of my inspections are in newer additions and areas with new water towers, etc. I see pressure problems that are related to areas with rapid growth and upgraded water infrastructure.

[Jim Luttrall]

Jim; Expansion tank installations require check valves on the inlet side (cold) to water heaters, making the hot system closed. TPR valves are also required.

Do you have a code cite for that? Never heard of a requirement to make a system closed just because you have an expansion tank.:confused:

[Tom Thompson]

Do you have a code cite for that? Never heard of a requirement to make a system closed just because you have an expansion tank.:confused:
If you review installation instructions Watts, Wilkins, Zurn web sites residential expansion tanks show some type of back flow device on inlet, followed by the ET. All are IPAMO approved, the approval is based upon compliance with the installation instructions. Inspectors are supposed to verify IPAMO approved installs were followed. I never really agreed with this, the idea is to absorb the minimal expansion created within the E- tank as designed and not through out the water system. TPR will blow off for run away heater as designed, the ET also saves the TPR from expansion stress leading drips.

[James Duffin]

If you review installation instructions Watts, Wilkins, Zurn web sites residential expansion tanks show some type of back flow device on inlet, followed by the ET. All are IPAMO approved, the approval is based upon compliance with the installation instructions. Inspectors are supposed to verify IPAMO approved installs were followed. I never really agreed with this, the idea is to absorb the minimal expansion created within the E- tank as designed and not through out the water system. TPR will blow off for run away heater as designed, the ET also saves the TPR from expansion stress leading drips.

I don't think the installation instructions are saying to install a backflow preventer to make the hot water system a closed system. The backflow device is normally where the water enters the house and cold to water heater and the cold to the house is connected after the backflow device. That is why the expansion tank does not have to be near the heater to work properly. It can be anywhere on the system after the check valve.

[Jim Luttrall]

If you review installation instructions Watts, Wilkins, Zurn web sites residential expansion tanks show some type of back flow device on inlet, followed by the ET. All are IPAMO approved, the approval is based upon compliance with the installation instructions. Inspectors are supposed to verify IPAMO approved installs were followed. I never really agreed with this, the idea is to absorb the minimal expansion created within the E- tank as designed and not through out the water system. TPR will blow off for run away heater as designed, the ET also saves the TPR from expansion stress leading drips.

I think you will find the expansion tanks are there because the check valve or PRV is there, not the reverse as you stated. In other words there is no requirement for a check valve to be installed just because an expansion tank or other device is present but there IS a code requirement for a thermal expansion device to be present on a closed system (i.e when a check valve or PRV is present).

[Tom Thompson]

I think you will find the expansion tanks are there because the check valve or PRV is there, not the reverse as you stated. In other words there is no requirement for a check valve to be installed just because an expansion tank or other device is present but there IS a code requirement for a thermal expansion device to be present on a closed system (i.e when a check valve or PRV is present).


Expansion tanks are only needed on closed systems, not all systems are closed and don't need E- tanks. Installations instructions indicate closed systems, E-tank won't benefit open systems and are basically useless, just something else to leak in time. A closed system is required for proper operation.

[Robert Foster]

Does anyone have a nice looking diagram/illustration of a water heater with an expansion tank installed they'd care to share?

[Jerry Peck]

Does anyone have a nice looking diagram/illustration of a water heater with an expansion tank installed they'd care to share?

See Figure 1 here: http://media.wattswater.com/2915054.pdf

[Robert Foster]

Thank you Jerry... a little time in photoshop and that will do nicely.

[Tom Thompson]

Expansion tanks are only needed on closed systems, not all systems are closed and don't need E- tanks. Installations instructions indicate closed systems, E-tank won't benefit open systems and are basically useless, just something else to leak in time. A closed system is required for proper operation.
Jim; You are correct, closed and city pressure exceeding relief valve set points require expansion tanks, helps the relief valves from excessive wear and leaks. Not required on other systems.

[Robert Foster]

Yesterday I think I ran into my first expansion relief valve instead of an expansion tank. The red valve was stamped as a Watts Regulator and the top knob was adjustable ? Am I correct ?

[Tom Thompson]

Yesterday I think I ran into my first expansion relief valve instead of an expansion tank. The red valve was stamped as a Watts Regulator and the top knob was adjustable ? Am I correct ?
It's not an expansion valve. It's been painted red. Are there any numbers on it? Looks like some kind of a steam fitting.

[Rod Smith]

Would the red pressure relief valve require any special considerations, like a TP valve on a hot water heater?(routing of discharged water, mounting location, etc.)? seems like if this is a good thing instead of an expansion tank, it would be more prevalent on installations (assuming that the cost of the valve is equal or cheaper than a tank.

[B___D__]

You seem to be going to great lenghts to avoid expansion tanks, why?

When you have a heat system, in addtion to TPRV, and pressure reducer valve, you also need an expansion tank. The expansion tanks helps the heating system maintain the proper pressure.

Exactly why wouldn't ANYONE attempt to look for an alternative to an expansion tank? I am, and I am certainly unapologetic about it. I've read quite a bit about them, and aside from the fact that regardless of the updated standards, they are being pushed on people who might not need them being as how they are not in "closed systems". Some information I've read indicates that they show no statistical improvement in the failure rate of hot water heaters, AND the tanks themselves are so prone to failure, that it seems to be a forgone conclusion that they will in fact one day fail and potentially create a huge mess.

I believe that there should be a perfectly acceptable substitute to an expansion tank, and one that is more reliable and less of a burden to install.