expansion tank

[cory nystul]

Is there a proper orientation for an expansion tank?

31397

[Rick Cantrell]

No, as long as it is supported, it should be good.

[Jerry Peck]

No, as long as it is supported, it should be good.

As long as it is "properly" supported ... and that is not.

[Rick Cantrell]

As long as it is "properly" supported ... and that is not.

I don't see the problem. Will you explain?

[Jerry Peck]

The expansion tank needs to be supported vertically, not off the horizontal tap of the tee.

Either off the vertical tap of the tee, or, (in this case) a support under the elbow which supports the tank - and the support should be secured to the elbow so the support can't move.

[Rick Cantrell]

The expansion tank needs to be supported vertically, not off the horizontal tap of the tee.

Either off the vertical tap of the tee, or, (in this case) a support under the elbow which supports the tank - and the support should be secured to the elbow so the support can't move.
I agree, what you describe would be better.
However, is there documentation showing it's required?

[Jerry Peck]

I agree, what you describe would be better.
However, is there documentation showing it's required?

Look at the manufacturer's installation instructions and what they show/state.

All of the ones I've seen show the expansion tank vertically above the tee they are tapped from/mounted to, and some show wall support brackets, I recall seeing some showing straps from above.

What I do not recall seeing are any which show support off the side of a tee.

[Jerry Peck]

This is a typical expansion tank installation instruction:
- http://media.wattswater.com/2915054.pdf

Notice that the vertical support shown for the:

Support Tank

in Optional

Horizontal

Position

Also notice that the pipe with the tee in it for vertical mounting (down is shown as the preferred position, up is shown as being an "optional" position) continues on.

Also this: (underlining is mine for highlighting - bold is from the installation instructions)
- 5. Install the expansion tank in the system (refer to Figure 1).
- - a. The weight of the expansion tank filled with water is supported by the system piping. Therefore, it is important that, where appropriate, the piping has suitable bracing (strapping, hanger, brackets).
- - b. The expansion tank may be installed vertically (preferred method) or horizontally. Caution: The tank must be properly supported in horizontal applications.
- - c. This expansion tank, as all expansion tanks, may eventually leak.
- - - - Do not install without adequate drainage provisions.

[Scott Patterson]

I had a plumber show me or tell me that I needed to test the air bladders in the tank. He said that about half will go bad in five years! You unscrew the plastic cap with the palm of your hand and then you will find a Schrader valve that you can depress and if air comes out then it is ok but if water or nothing comes out the bladder has failed!

Has anyone every heard about testing expansion tanks?

[Vern Heiler]

I had a plumber show me or tell me that I needed to test the air bladders in the tank. He said that about half will go bad in five years! You unscrew the plastic cap with the palm of your hand and then you will find a Schrader valve that you can depress and if air comes out then it is ok but if water or nothing comes out the bladder has failed!

Has anyone every heard about testing expansion tanks?
My retired neighbor/plumbing contractor has the same opinion of expansion tanks, he favored the valve type expansion relief devices. If the valve is depressed to test the condition of the bladder, someone is going to have to re-set the pre-charge pressure and that takes turning the water off and emptying the system. Beyond the scope of a HI.

[Ian Page]

Don't see very many expansion tanks but have read quite a bit about them since the last post dealing with them. Nothing that I've read from a variety of manufacturers allow for the tank to be inverted. I've emailed Watts, seeking an opinion as to whether inverting the tank affects its performance or prevents servicing.

[Jack Feldmann]

A plumber told me the same thing. I do tap on them, because you can tell if they are full of water. I'm not sure checking if air comes out, or the pressure with a tire gauge is going to result in having to reset the pressure.
My most common write up is for poorly supported, or non supported tanks.

[Garry Sorrells]

Don't see very many expansion tanks but have read quite a bit about them since the last post dealing with them. Nothing that I've read from a variety of manufacturers allow for the tank to be inverted. I've emailed Watts, seeking an opinion as to whether inverting the tank affects its performance or prevents servicing.


Years ago before the expansion tanks had a bladder in them the tank would have the inlet in the bottom and set vertically. There would be a valve that you would use to pump up the tank. If the system was drained the pressure would be lost and the tank would have to be pressurized. Bicycle Pump worked, just a lot of pumping. The introduction of the tanks with bladders allowed for the alternate positioning of the tanks since the sealed bladder in the tank would maintain the pressure even if had no water or in different orientations.

So, if the tank is in the "optional" vertical position, inlet on the bottom, and the bladder were to break the air would not escape and the pressure would be maintained within the tank.

Checking the tank with a tire gauge would tell you if the tank is operating correctly. Pressure loss is minimal if you don't make a mess of taking the pressure. If you know the pressure then you know it is functioning. Else you are checking to see if the tank is full of water and the bladder has failed letting a very minimal amount of air out, where minimal is the operative word, works. You just can not try to dry you hair as you check the tank.

Checking the tank is a good idea so long as you know what you are doing and why.

[Jerry Peck]

Nothing that I've read from a variety of manufacturers allow for the tank to be inverted.

The installation instructions I posted were from Watts for their expansion tank.

While the instructions don't address any change in performance between vertically up, vertically down, or even horizontal installations - the instructions specifically permit vertically down (preferred), vertically up (optional), and even horizontal with support (optional).

[Vern Heiler]

Years ago before the expansion tanks had a bladder in them the tank would have the inlet in the bottom and set vertically. There would be a valve that you would use to pump up the tank. If the system was drained the pressure would be lost and the tank would have to be pressurized. Bicycle Pump worked, just a lot of pumping. The introduction of the tanks with bladders allowed for the alternate positioning of the tanks since the sealed bladder in the tank would maintain the pressure even if had no water or in different orientations.

So, if the tank is in the "optional" vertical position, inlet on the bottom, and the bladder were to break the air would not escape and the pressure would be maintained within the tank.

Checking the tank with a tire gauge would tell you if the tank is operating correctly. Pressure loss is minimal if you don't make a mess of taking the pressure. If you know the pressure then you know it is functioning. Else you are checking to see if the tank is full of water and the bladder has failed letting a very minimal amount of air out, where minimal is the operative word, works. You just can not try to dry you hair as you check the tank.

Checking the tank is a good idea so long as you know what you are doing and why.
You do know the water supply has to be turned off and all the water pressure in the system has to be relieved before you can check the pressure right.

[Vern Heiler]

The installation instructions I posted were from Watts for their expansion tank.

While the instructions don't address any change in performance between vertically up, vertically down, or even horizontal installations - the instructions specifically permit vertically down (preferred), vertically up (optional), and even horizontal with support (optional).

I believe the support in the horizontal position is to protect the fitting in the end of the tank, not necessarily the pipe. Must be supported is only if installed horizontally.

a. The weight of the expansion tank filled with water is supported bythe system piping. Therefore, it is important that, where appropriate,the piping has suitable bracing (strapping, hanger, brackets).
b. The expansion tank may be installed vertically (preferred method)or horizontally. Caution: The tank must be properly supportedin horizontal applications.

The OP's tank is vertical and I think you could do pull-up's on that galvanized pipe that is supporting the tank. It would require support if the pipe was plastic which would be "where appropriate".

[Jerry Peck]

I believe the support in the horizontal position is to protect the fitting in the end of the tank, not necessarily the pipe. Must be supported is only if installed horizontally.

The tank must be supported horizontally to support the weight of the tank ... that is to take the weight off where the tank connects to the piping - whether that be for the pipe fitting on the end of the tank or the pipe fitting the tank mounts too does not matter, the solution to addressing either ... and both ... is to support the weight of the tank.


a. The weight of the expansion tank filled with water is supported bythe system piping. Therefore, it is important that, where appropriate,the piping has suitable bracing (strapping, hanger, brackets).

Vertically, yes, and if the tank is installed vertically off a horizontal tap off the piping, the above applies (bold and underlining is mine) "Therefore, it is important that, where appropriate, the piping has suitable bracing (strapping, hanger, brackets).", i.e., support the weight of the tank by supporting the piping.


The OP's tank is vertical and I think you could do pull-up's on that galvanized pipe that is supporting the tank. It would require support if the pipe was plastic which would be "where appropriate".

And it is "appropriate" to be supported at that elbow below the tank. ;)

We have engineers here, what is the weight of that tank at the end of that horizontal lever sticking out from the side of that tee? :)

That said ... :p ... piping is not to be used to support anything.

[John Kogel]

It would require support if the pipe was plastic which would be "where appropriate".

How about dangling from PEX pipe in the crawlspace? Yes they use the cheap plastic pipe clamps too. New construction.
I see them poking out sideways all the time in new construction and almost never supported with a strap or a bracket. What is wrong with these people, plumbers, that don't understand the basic laws of their trade, such as the force of gravity? Instruction manual? Can you read? :confused:

[Jerry Peck]

What is wrong with these people, plumbers, that don't understand the basic laws of their trade, such as the force of gravity? :confused:

They understand the laws of gravity, they will be the first to remind anyone and everyone that $hit flows downhill. :)


Instruction manual? Can you read?

They would have to be able to read to read the title "Installation Instructions". ;)

[Vern Heiler]

The tank must be supported horizontally to support the weight of the tank ... that is to take the weight off where the tank connects to the piping - whether that be for the pipe fitting on the end of the tank or the pipe fitting the tank mounts too does not matter, the solution to addressing either ... and both ... is to support the weight of the tank.



Vertically, yes, and if the tank is installed vertically off a horizontal tap off the piping, the above applies (bold and underlining is mine) "Therefore, it is important that, where appropriate, the piping has suitable bracing (strapping, hanger, brackets).", i.e., support the weight of the tank by supporting the piping.



And it is "appropriate" to be supported at that elbow below the tank. ;)

We have engineers here, what is the weight of that tank at the end of that horizontal lever sticking out from the side of that tee? :)

That said ... :p ... piping is not to be used to support anything.
Do you mean like shown in fig.1 where the pipe is supporting the vertically hung tanks with no support?

[Jerry Peck]

Do you mean like shown in fig.1 where the pipe is supporting the vertically hung tanks with no support?

Yep. :)

But at least that pipe is supported to the right and left of the expansion tank ... supposed to be supported any way.

I'll look up the code reference later when I get a chance.

[Mark Reinmiller]

I had a plumber show me or tell me that I needed to test the air bladders in the tank. He said that about half will go bad in five years! You unscrew the plastic cap with the palm of your hand and then you will find a Schrader valve that you can depress and if air comes out then it is ok but if water or nothing comes out the bladder has failed!

Has anyone every heard about testing expansion tanks?

I do it all the time if they are more that a few years old. I find a surprising number that have failed.

As far as support goes, the instructions I have read suggest hanging them vertically or supporting them if horizontal, but that may not apply to all size tanks. I agree that the one shown is bad. That tank would put quite a bit of stress on the Tee.

[Ian Page]

The installation instructions I posted were from Watts for their expansion tank.

While the instructions don't address any change in performance between vertically up, vertically down, or even horizontal installations - the instructions specifically permit vertically down (preferred), vertically up (optional), and even horizontal with support (optional).

Jerry, I must admit I didn't use you link, duh! But didn't see anything on the Watts installation instructions I went to. Thanks.
Watts diagram makes it pretty clear but they haven't responded to my query yet.
As most ETs are fitted with a schrader valve, or similar. I wonder is it common practice to release some air during an inspection or simply disclaim functionality? Even releasing air doesn't tell a whole lot. I still haven't run across one installed, yet.

[Jerry Peck]

Ian,

I would not recommend releasing air - was the air at proper pressure ... if so, it isn't after the air is released.

I would include in the report the high rate of failure and that the proper way to test is to shut the plumbing system down and release all pressure. I would like then include the cost of replacing the tank, explaining the the cost to properly test the tank is likely about the same as the cost to replace the tank.

[Mark Reinmiller]

I do not check them with a gauge, but not a bad idea. The amount of air I release is not small it would not make a difference. This does not tell you whether the tank is properly charged, but does find failed tanks, which is more important from an inspection standpoint.

[Bob Harper]

The tank, as installed may work but is not optimal. All bladder/ diaphragm tanks should be installed with the Schrader valve down. That way, when depressed, if water has breaked the seal, it will manifest at the Shrader. A simple test with a standard air pressure gauge should not release sufficient air to drop the pressure below an acceptable level if it was previously properly charged.

Since the tank charge can be properly tested only when isolated from the house pressure, every tank should be installed with a ball valve and drain. I use these on boiler tanks: Expansion Tank Pro Service Valve (http://www.webstonevalves.com/default.aspx?page=customer&file=customer/wecoin/customerpages/expansiontank.htm)

It is actually uncommon for an installer to charge a tank at installation.

[Mike Borchardt]

Is there a proper orientation for an expansion tank?

31397

Can someone help me out? I see a TPR valve and a gas line so I believe this is a hot water heater. I've seen alot of hot water heaters. I've never seen an expantion tank on one. Whats its purpose?

[Chris Weekly]

The picture shows a gas-fired water heater, and a TPR valve and drain line; with an expansion tank on top of the water heater. These devices shown are next to a gas-fired furnace - you can see its' yellow gas flex connector tubing. The gas connector for the water heater is not shown.
The expansion tank is to minimize extreme pressure fluctuation in the water piping system. Quick on and off of a valve in the water piping system may cause 'knocking' of the water pipes - its' hard on pipes and joints and may cause leaking. The expansion tank bladder helps relieve stress in a closed system.

[Mark Sokalski]

Can someone help me out? I see a TPR valve and a gas line so I believe this is a hot water heater. I've seen alot of hot water heaters. I've never seen an expantion tank on one. Whats its purpose?


One gallon of water at 60oF expanse to 1.016 gallons when heated to 140F. If the tank is 40 gallons, then the water volume grows 0.64 gallon or 2-1/2 quarts. This addition volume either goes: 1) into expanding the volume of the tank, hoses, and pipes until the pressure reaches the relief valve setting, then drips, or 2) flows backwards out into the supply, or 3) flow into the expansion tank. An expansion tank also increases the life of the water heater tank by reducing the fluctuating pressure range.

1/2" male NPT tanks are rated for low pressure hydronic boilers (30 psig max)

3/4" male NPT tanks are rated for potable water pressure (typically, 150 psig max) and the good ones have a plastic liner in contact with the potable water.

Rules 101 for installing an expansion tank:


Pre-charge the expansion tank with air to about 2 to 5 psi more than the operating water pressure at the install location.
Install the tank hanging down from the cold water pipe, support as necessary.
A shutoff valve and a bleed valve should be installed between the tank and the cold water pipe.
Make sure you have physical access to the air fill valve. This air fill valve is also used to check to see if the internal diaphragm has a leak and must face downward.
Mark the date of install and the pre-charge pressure on the tank with a permanent black marker.
Every 6 months or so, open and close a sink valve to remove any recently expanded water, close the expansion tank's shut-off valve, open the bleed valve, and then verify the pre-charge pressure. If the tank is operating properly very little water will come out the bleed valve and no water will come out of the air fill valve. Only check and recharge the exp. tank with the exp. tank removed from the system or with the bleed valve open.

[Mike Borchardt]

Because of its location and size, I thought it might have a different purpose other than being a centralized shock absorber as someone posted. I just watched an installation of a well system where a water tank was not used but an expansion tank was installed at the water inlet inside the building. Nowhere near the hot water tank.

[Dave Ruth]

Can someone help me out? I see a TPR valve and a gas line so I believe this is a hot water heater. I've seen alot of hot water heaters. I've never seen an expantion tank on one. Whats its purpose?Thermal expansion, especially at nite when water is not being used, raises pressure on cold water line in a closed system, such as after the back flow preventer.

[Harry Janssen]

I had a plumber show me or tell me that I needed to test the air bladders in the tank. He said that about half will go bad in five years! You unscrew the plastic cap with the palm of your hand and then you will find a Schrader valve that you can depress and if air comes out then it is ok but if water or nothing comes out the bladder has failed!

Has anyone every heard about testing expansion tanks?

Scott,thats how I test them.

[Mark Reinmiller]

Here is some additional input regarding support. I just installed a Watts expansion tank. The instructions that came with it (for Models DET-5-M1, DET-12-M1, and DET-20-M1) show it hanging vertically. Optional positions are shown as vertical with the thread joint at the bottom and horizontal. There is a note stating to support tank in the horizontal position.

I just did a new construction house with a Mainline expansion tank (the parent company is Amtrol). They show the tank hanging vertically, but have nothing in the instructions specifying position or support. I checked Amtrol's instructions also and they are the same.

I think horizontal support is a good idea (especially with plastic pipe), but apparently not always required. I have seen a few that bent down. I don't recall, but there is probably a good chance that the bladder failed if you see that.

[Jerry Peck]

Mark,

Or maybe the tank is only supposed to be hung vertically?

[Ian Page]

Mark,

Or maybe the tank is only supposed to be hung vertically?
The reply I received from Watts basically said they recommend the tank to be hung vertically, with ready access to the schrader valve for pressurization and testing.

"Thank you for your inquiry, I understand you have a concern regarding the position of our thermal Expansion tanks. See the Installation sheet, as a vertical up position is hard to check bladder damage for water / air. Floor mount larger tanks have one position only.

Thank you again for your interest in Watts's products."

Sincerely,
Watts Technical Service Team

[Mark Reinmiller]

Mark,

Or maybe the tank is only supposed to be hung vertically?

Maybe, but I think they should clarify that.

p.s. Not that I expect a contractor to pay attention to the instructions, but it makes it easier for us to prove when they are wrong.

[Jerry Peck]

Maybe, but I think they should clarify that.

p.s. Not that I expect a contractor to pay attention to the instructions, but it makes it easier for us to prove when they are wrong.

Agree on both.