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Old 04-20-2012, 05:19 PM   #1
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Installation and support of water heater expansion tanks.


INSTALLATION AND SUPPORT OF EXPANSION TANKS - PART 1 of 2:
(Presented in 2 parts due to length restrictions of the forum.)

After doing much research in the past on water heater expansion tank installations, I'd like to share some installation procedures that might be helpful to DIY'ers who want to install one. Some procedures that I thought of are not posted anywhere else that I could find so be aware they are just my own thoughts so use them at your own discretion. Any comments or corrections are welcome.

WHY DO I NEED A WATER HEATER THERMAL EXPANSION TANK?
------------------------------------------------------------------------
See this link for an explanation:
http://www.watts.com/pages/learnAbout/thermalExpansion.asp?catId=64


WHERE TO INSTALL, AND THE ORIENTATION OF THE TANK:
------------------------------------------------------------------
Expansion tanks can be installed anywhere in the plumbing system but that is providing that there is no shut off valve between the expansion tank and the water heater. IOW, when the shut off valve is closed, the expansion tank can still absorb excess pressure created by heating water in the heater.

Some residential expansion tanks will say that they should be installed in a hanging vertical position. But from my research, they can be installed in any orientation. Here's one website that confirms this observation:

http://www.fastwaterheater.com/expansiontanks.htm

The instructions that come with the Watts DET line of expansion tanks say that they can be installed horizontally, or vertically with the water connection on top or on the bottom of the tank.

WHAT KIND OF CONNECTION DOES AN EXPANSION TANK HAVE?
------------------------------------------------------------------------
The Watts DET-12 expansion tank has a 3/4" threaded male fitting. I believe that most if not all residential water heater expansion tanks will have this type of connection.

WHAT KIND OF EXPANSION TANK TO BUY?
------------------------------------------------
For use in a residential plumbing system, be sure to buy an expansion tank that's rated for "potable" water systems. There are expansion tanks for "non-potable" systems and I don't think folks would want to drink water from systems with a non-potable rated expansion tank.

END OF PART 1


Last edited by Homerepairguy; 04-21-2012 at 05:53 AM.
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Old 04-20-2012, 05:20 PM   #2
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Installation and support of water heater expansion tanks.


INSTALLATION AND SUPPORT OF EXPANSION TANKS - PART 2 of 2:

SUPPORTING THE EXPANSION TANK:
-----------------------------------------
This is the major point of this post. Support of expansion tanks is not covered in enough detail in my opinion. Here's why:

A new Watts DET-12, 4.5 gallon expansion tank weighs 7.8 lbs. When it's installed and working properly, some water will enter the tank but the weight will not be too excessive. However, when (not if) the internal bladder of any expansion tank fails, water can fill the tank. Water weighs about 8.34 lbs per gallon. A 4.5 gallon expansion tank will weigh 37.5 lbs + 7.8 lbs = 45.3 lbs. A 5 gallon expansion tank full of water including the weight of the tank itself will weigh 49.5 lbs. So support of an expansion tank is so very important!

VERTICAL HANGING INSTALLATION:
Just hanging a 5 gallon expansion tank from a soldered "T" fitting will be exerting about 50 lbs on the soldered connections if/when the tank fails. With the constant expansion and contraction of the pipes, fittings and solder joints because of cold water and heated water and a 50 lb weight, I believe the solder joints could fail dropping the tank and causing major flooding.


VERTICAL OVER THE COLD WATER INPUT PIPE INSTALLATION:
I've seen installations that place the expansion tank directly above the cold water input to the water heater with no other support. (See picture below) Now if the 5 gallon expansion tank gets full of water, there will be 50 lbs of weight stressing the copper pipes and fittings while they expand and contract many times a day due to cooling and heating. This could cause leaks. In addition, depending on the length of the pipe from the water heater to the tank and whether the tank is "directly centered" over the pipes, the 50 lbs of weight could cause the tank to lean on one side and possibly result in the tank falling over and breaking the water line.

HORIZONTAL INSTALLATION:
The horizontal installation is good if the tank is properly supported by a shelf or a metal strap. A failed 50 lb tank will not put stress on pipes, fittings or soldered connections and the copper pipes are free to move with contraction and expansion, unlike if the tank is installed directly over the cold water line of the tank.

THE BEST WAY TO SUPPORT AN EXPANSION TANK:
---------------------------------------------------------
I've come to the conclusion that the best way to support an expansion tank is to install it on a shelf with the water connector facing down, off to the side of the water heater.


This installation accomplishes the following:

1. The weight of a failed tank will be supported entirely by the shelf with no stress on any pipes, fittings or soldered connections. No chance of a 50 lb failed tank falling off like in an unsupported hanging installation.

2. With the tank and shelf installed on a wall offset from the water heater, the horizontal run of the pipe from the water heater to the tank is free to move on a daily basis due to expansion and contraction without the weight of the tank stressing things like if the tank is installed directly over and supported by the cold water input pipe to the heater.

3. *** Here's a biggie reason to have the tank installed with the water connection facing down. ***
If the water connection is facing up and the tank fails and gets full of water, it will be very difficult to remove a 50 lb tank in confined spaces. --- If the water connection is facing down, then the water can "easily" be drained out of the tank and then the tank can easily be removed.


4. *** Another biggie reason to have the tank installed with the water connection facing down. ***
In a hanging installation, if the internal bladder ruptures, the air will quickly go to the top of the tank and be expelled. Water will quickly and completely fill the tank to the brim. --- With the water connection facing down, the air will be trapped on the top of the tank and the tank can act like an air chamber hammer arrestor until the air is "gradually" depleted. This can give the home owner time to discover the rupture and replace the tank.

Note:
Since the water connection is facing down, the shelf will have to have a hole in it or two metal angle brackets could be used to support the tank. The hole in a 3/4" wooden shelf should be large enough and tapered to allow the tank to sit further down and allowing the hex nut on the fitting to be below the bottom of the shelf and thus be accessed when tightening the connection. (The convex shape of the tank at the water connection allows the hex nut to be below the shelf.)

As mentioned at the beginning, these are just my observations and thoughts in installing a water heater expansion tank. Thousands of expansion tanks are installed in the hanging position or directly above the water heater cold line but I won't do it on my home for the reasons mentioned. Over thinking the installation? Probably but that's what I always do.

Hope this helps some folks. I would love any comments if this helps you install your expansion tank. If you find fault with my thoughts, I'd like to hear them too to learn things that I've not thought of.

HRG


Last edited by Homerepairguy; 04-22-2012 at 11:05 PM.
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Old 04-20-2012, 06:31 PM   #3
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Installation and support of water heater expansion tanks.


nice job
you could just use an expansion tank bracket like this one
http://www.watts.com/pages/_products...s.asp?pid=7232

also if fastwaterheater says to connect tank with a saddle valve which a saddle valve is not legal here. it makes it hard for me to agree with them on mounting and to disregard manufactures instructions and if it fails and the manufacture does not cover since it was not mounted correctly will they pay the expense
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Old 04-20-2012, 06:50 PM   #4
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Installation and support of water heater expansion tanks.


Quote:
Originally Posted by jaydevries View Post
nice job
you could just use an expansion tank bracket like this one
http://www.watts.com/pages/_products...s.asp?pid=7232

also if fastwaterheater says to connect tank with a saddle valve which a saddle valve is not legal here. it makes it hard for me to agree with them on mounting and to disregard manufactures instructions and if it fails and the manufacture does not cover since it was not mounted correctly will they pay the expense
Thanks. That bracket is a really nice, easy way to support an expansion tank. Saves a lot of work building a shelf like I did. The flexible corrugated stainless steel hose makes connection to the expansion tank very easy.

EDIT: BTW, FastWaterHeater says:
***** Retail expansion tanks come with a "Saddle Fitting", which allows the installation into the system without any soldering, thereby making installation easier for the average homeowner. The saddle fitting is a device that clamps around the pipe and has female threads that will accept the expansion tank. A small hole is first drilled in the pipe, then the clamp is placed so the hole lines up with the expansion tank inlet. We do not recommend using such a fitting. They are unreliable, and allow placement of the expansion tank in the above mentioned vertical hanging position only. *****

Saddle fittings are totally out in my view.

Thanks much for the link. I'm sure it will be very helpful to everyone.
HRG

Last edited by Homerepairguy; 04-21-2012 at 12:32 AM.
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Old 04-20-2012, 09:32 PM   #5
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Installation and support of water heater expansion tanks.


If the tank is mounted above the pipe it is attached to (open end down) then it may continue to work properly for awhile if the bladder should break. It may continue to work indefinitely if more air is added from time to time to replace the air gradualy absorbed by the water.

The only problem is if the bladder tears in a manner that it herniates into and thus blocks the pipe connection.
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Old 04-20-2012, 10:33 PM   #6
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Installation and support of water heater expansion tanks.


Quote:
Originally Posted by AllanJ View Post
If the tank is mounted above the pipe it is attached to (open end down) then it may continue to work properly for awhile if the bladder should break. It may continue to work indefinitely if more air is added from time to time to replace the air gradualy absorbed by the water.

The only problem is if the bladder tears in a manner that it herniates into and thus blocks the pipe connection.
Hi AllanJ,

Those are very good points that I had not considered. Especially the part about a torn bladder possibly blocking the pipe connection.

Thanks a lot for your input,
HRG
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Old 04-21-2012, 08:56 AM   #7
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Installation and support of water heater expansion tanks.


We always install ours whenever possible with : Brass tee on cold inlet of water heater, expansion tank threaded directly into the top of the tee, and a 4 or 6" pipe nipple in the tee to give the water heater supply room to flex around the tank and back to the valve.


There are no support issues with this installation.
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Old 04-21-2012, 02:20 PM   #8
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Installation and support of water heater expansion tanks.


Quote:
Originally Posted by Alan View Post
We always install ours whenever possible with : Brass tee on cold inlet of water heater, expansion tank threaded directly into the top of the tee, and a 4 or 6" pipe nipple in the tee to give the water heater supply room to flex around the tank and back to the valve.

There are no support issues with this installation.
Hi Alan,

Sounds like a solid way to install an expansion tank but I'm not sure I'm picturing the installation correctly. Could you link to a picture of the kind of brass tee you use? How is the tee oriented?

Right now I'm picturing this:

Is this correct?

If yes, do you use a copper or stainless steel corrugated flex line from the 6" nipple to the shutoff valve?

Thanks for your input,
HRG

Last edited by Homerepairguy; 04-22-2012 at 11:06 PM.
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Old 04-21-2012, 03:34 PM   #9
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Installation and support of water heater expansion tanks.


How to properly charge your tank
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Old 04-21-2012, 04:28 PM   #10
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Installation and support of water heater expansion tanks.


Quote:
Originally Posted by TheEplumber View Post
Hi Eplumber,

Thanks for your contribution to this thread.

I've seen that Watt's pre-charge video before. Although the narrator says to use a hand or electric pump to pre-charge the tank, he should have mentioned never to use compressed air from a service station or similar device that has compressed high air pressure.

I know that you already know this but for folks new to expansion tanks, uncontrolled high air pressure entering the tank can damage the internal bladder. Air pressure must "gradually build up" to pre-charge the tank to match the home's water pressure (but never more than 80 psi).

Thanks,
HRG
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Old 04-21-2012, 09:42 PM   #11
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Installation and support of water heater expansion tanks.


Quote:
Originally Posted by Homerepairguy View Post
Hi Alan,

Sounds like a solid way to install an expansion tank but I'm not sure I'm picturing the installation correctly. Could you link to a picture of the kind of brass tee you use? How is the tee oriented?

Right now I'm picturing this:
Code:
          ---
         |   | <==Expansion tank screwed directly into brass tee 
         |   |
          ---     ---6" nipple screwed into brass tee
           |     /
          | |   /
          | |-----___(flex line to shut off valve)____(shut off valve)
          | |-----
          | |<======Brass tee screwed on male nipple from tank.
           |
 ---------------
|               |
|               |
|               |
Is this correct?

If yes, do you use a copper or stainless steel corrugated flex line from the 6" nipple to the shutoff valve?

Thanks for your input,
HRG
Something like this : http://www.hardwarestore.com/media/p...2_front200.jpg

Yes, we use copper or stainless flex depending on what type of piping is installed in the house.
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Old 04-22-2012, 04:10 AM   #12
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Installation and support of water heater expansion tanks.


Quote:
Originally Posted by Alan View Post
Something like this : http://www.hardwarestore.com/media/p...2_front200.jpg

Yes, we use copper or stainless flex depending on what type of piping is installed in the house.
Thanks for the link to the brass tee. So I assume that my drawing is correct. That does indeed look like a solid way to mount an expansion tank. All screw joints from the heater up to the expansion tank so no worries about a heavy failed tank stressing soldered copper fittings.

Thanks for letting us know of a simple but strong way to install an expansion tank above the heater.

HRG
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Old 04-22-2012, 04:35 AM   #13
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Installation and support of water heater expansion tanks.


The brass tee that Alan linked to for installing an expansion tank directly above the water heater made me realize that a brass tee could be used to install a hanging expansion tank.

By not using a soldered copper tee and using a threaded brass tee instead, the tank would be "screwed" into the brass tee preventing the tank from dropping if the tank failed and got full of water. I think a metal strap needs to be installed from the brass tee to a strong upper support to prevent the copper pipes from bending down due to a failed 50 lb tank hanging from the pipes.

I still don't like an expansion tank installed with the water connection facing up because of reasons 3 & 4 in post #2, but at least using a threaded brass tee, there's no chance of soldered connections failing and dropping a heavy failed tank.

HRG

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Old 04-22-2012, 07:21 AM   #14
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Installation and support of water heater expansion tanks.


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Old 04-22-2012, 07:31 AM   #15
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Installation and support of water heater expansion tanks.


repairguy:

was this how you used a shelf to support yours on the horizontal installatin?
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