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-   -   Expansion Tank (http://www.diychatroom.com/f7/expansion-tank-181145/)

jagans 06-02-2013 07:00 PM

Expansion Tank
 
I think I asked this question a few times before, but do hot water heaters piped in series with a well expansion tank need a separate expansion tank above the hot water heater by code? And if they do, what is the logic behind this, as there is already expansion provided by the well tank, and it has never been done in the past?

Thanks Guys.

I like logic. The NEC is Logical.

TarheelTerp 06-02-2013 07:07 PM

Quote:

Originally Posted by jagans (Post 1193659)
...do hot water heaters need a separate expansion tank ...

I don't think they're **needed** at all for most installs.

Until city water pressure was boosted... I'd say none at all.
Now? When the WH is installed in living space.
In unfinished basement? Nah.

Ghostmaker 06-02-2013 07:47 PM

The IPC requires a hot water expansion control device if there is a check valve on the main water feed or reducing valve. A well pressure tank is not a hot water expansion control device. The bladder in a well pressure tank is rated for cold water use only.

In Ohio plumbing inspectors are required to apply the most rigorous standard. Code is the first to be applied then manufacture install instructions as a secondary. Out of the 2 which ever is the tuffer will apply.

If you care to look at your installation guidelines of most hot water tanks you will find an expansion control device as required. Code also requires it.

If you do not install one and your tank fails you leave an opening to void the warranty of your heater.

Daniel Holzman 06-02-2013 08:00 PM

Ghostmaker, I don't follow your post at all. You describe a check valve on the main water feed. I have never seen a check valve on a main water feed in a well system, which is what the OPS apparently has. The only time I have seen a check valve in a residential application is on a city water supply, or for a hot water boiler supply system.

Now as for whether a well expansion tank is suitable for use as a hot water expansion tank, so far as I know it is just fine, that is exactly what I have in my house. All of the water lines in a house are connected, since the hot water tank is fed from a cold water line. Unless you happen to have a check valve on the cold water feed to your hot water tank, which would be unusual, at least I have never seen it done. So when the water in the hot water tank wants to expand, it will simply expand into the well expansion tank. As for a boiler, that typically has its own expansion tank, since the boiler system is typically fed from the cold water line using a check valve, hence it is an isolated system, and requires a separate expansion tank.

Ghostmaker 06-02-2013 08:06 PM

Every well system has a check valve and a foot valve in Ohio. We prefer not allowing a household to contaminate the water table.

I'm just telling you the code. Do what you want but if I inspected it I would red tag you as a violation.

jmon 06-02-2013 08:06 PM

This question has come up a few times on this forum.

I am not sure, but I believe it was gregzoll who said, If you have a well and there already is an expansion tank, and you don't have any check valve in between the well expansion tank and the hot water tank, then you should be fine to operate without the additional expansion tank on hwh. Searching past posts for you.

joed 06-02-2013 08:59 PM

The reason for the expansion tank on hot water is to allow the water some place to expand to instead raising the pressure in the system as water heats.
In a normal home the water can expand back into the water main. If you have pressure reducing valve then you need an expansion tank as they act as a check valve.
In a well system unless you have a check valve AFTER the pressure tank the water can expand back into the clod line and the system tank will absorb it. i don't think you need it.

The foot valve has nothing to do with protecting the aquifer. It is there to keep the water from flowing out of the pressure tank when the pump shuts off, and to allow the pipe to be primed if the pump is a shallow well version.

TheEplumber 06-02-2013 09:44 PM

Quote:

Originally Posted by Ghostmaker (Post 1193709)
The IPC requires a hot water expansion control device if there is a check valve on the main water feed or reducing valve. A well pressure tank is not a hot water expansion control device. The bladder in a well pressure tank is rated for cold water use only.

In Ohio plumbing inspectors are required to apply the most rigorous standard. Code is the first to be applied then manufacture install instructions as a secondary. Out of the 2 which ever is the tuffer will apply.

If you care to look at your installation guidelines of most hot water tanks you will find an expansion control device as required. Code also requires it.

If you do not install one and your tank fails you leave an opening to void the warranty of your heater.

I'm siding with you in this debate:yes:
A well has an expansion tank for pressure-it's not rated as a thermal expansion tank. How does this affect the fine print of your water heater warranty?

Also, per code, the thermo exp. tank should not have any valves between it and the tank- how will you install a shut off on the water heater then if the pressure tank is used for the thermo expansion tank?

jagans 06-02-2013 10:26 PM

Every HW expansion tank I have seen is located on the cold side inlet. In my case, if you go about one foot up, five feet horizontal and down you have the well expansion tank. When the HWH heats up, and the water in it expands, pressure increases on both the cold incoming leg, and the hot outgoing leg, pressure would therefore rise in the well expansion tank.

I Have to agree with Daniel Holzman on this as his logic is generally bullet proof, as I have found it in this case.

I do not mind installing an expansion tank, and will probably do so, as I need to drain my tank to install a new gas valve, but for the life of me, I cannot see why these things are now necessary, when they have never been necessary in the past. The purpose of the thermal relief valve is to release pressure that the HW tank cannot handle, is it not?

I do not like the attitude behind, "Because its required by code, and I will fail you if you don't have one" If the function of something that is required by code is not easily understandable in layman's terms, you have to wonder what prompted the change.

Thanks for all the information.

TheEplumber 06-02-2013 10:48 PM

Given your description- I'd pull the first 90 and replace it with a tee and FIP adpt. Screw the tank into it. It will be self supporting that way.

I've replaced a few Robert Shaw valves that went bad. You can do it without draining the tank and lose only a small amount of water- you can wipe it up with a paper towel.
Prep your new valve with dope or tape or what ever flavor you like.
Close the CW valve and relieve the tank presure through a faucet.
Now make sure all faucets are off so no air can enter the system.
Loosen the old valve, unscrew it out and quickly screw the new one in.
Sounds odd I know, but the tank will only gurgle like an upside down pop bottle once or twice- just a couple ounces. Just don't stop mid stream for a smoke break :whistling2:

TarheelTerp 06-02-2013 11:39 PM

Quote:

Originally Posted by jagans (Post 1193862)
I cannot see why these things are now necessary, when they have never been necessary in the past.

I think it's mostly about higher water pressure on municipal systems today (and PRV's) and more frequently installing WH's in the living space.

jagans 06-03-2013 12:53 PM

Quote:

Originally Posted by TheEplumber (Post 1193878)
Given your description- I'd pull the first 90 and replace it with a tee and FIP adpt. Screw the tank into it. It will be self supporting that way.

I've replaced a few Robert Shaw valves that went bad. You can do it without draining the tank and lose only a small amount of water- you can wipe it up with a paper towel.
Prep your new valve with dope or tape or what ever flavor you like.
Close the CW valve and relieve the tank presure through a faucet.
Now make sure all faucets are off so no air can enter the system.
Loosen the old valve, unscrew it out and quickly screw the new one in.
Sounds odd I know, but the tank will only gurgle like an upside down pop bottle once or twice- just a couple ounces. Just don't stop mid stream for a smoke break :whistling2:

Thank You EP, for the tip, but I think Ill drain the tank and look in there with my boroscope just for the heck of it. This WH came with an aluminum anode, and I subsequently bought a Mag anode, so I think Ill put that in too while I'm at it.

With the kind of luck I have, I would be in the middle of changing out the valve and someone would walk in and turn the water on upstairs, and I would get soaked.

Id rather be sorry than safe if you know what I mean.

By the way, you don't know any way that I could bypass the electronics in this assinine valve and get the tank to light off, do you? I could sit right next to it and let it heat up some water for a shower, then disconnect it. I know the recycle time and I have a laundry sink right near the HWH where I can monitor the temperature constantly. I can email you the pdf of the service manual for the valve with the schematic.

Don't worry, if I blow my head off I wont say it was your fault. :thumbup:

Thanks E, and thanks to all of you for your valuable input.

TheEplumber 06-03-2013 01:29 PM

Sorry, I can't think of a way to bypass it. It's one of "life safety" things that I never tried to figure a way to work around. From an installers point of view- it's much better to put in the replacement parts.

I worked at a shop that put in a bunch of defective heaters once. We had to suffer through a Robert Shaw gas valve recall. We had to beg our distributor to send us a 1/2 dozen valves to keep on the shelf for situations similar to yours. Between RS and the distributor, it was like pulling teeth to get them prior to sending back the defective one- not to mention reimbursement for our warranty labor. Dealing with homeowners in your situation wasn't fun either. A couple times we just flat out replaced the heaters and ate it.


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