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Should a valve be plumbed before and after expansion tank?  Rating:  Rating
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 Posted: Mon Jan 2nd, 2012 08:02 am
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Realmacaw
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I'm plumbing an expansion tank on the cold water side of a water heater.  Is it best to plumb a ball valve before AND after the expansion tank, or just before it?

There already is a main ball valve for the entire house.  But my thinking is if there is a problem with the expansion tank or water heater, it would be nice to not have to rely on that valve to turn off water to the expansion tank and water heater while repairs are being done.

Therefore, I can see why plumbing a valve before an expansion tank is a good idea.  But if there is also not a valve after the expansion tank, even with the valve before the expansion tank closed wouldn't the 5 gallon expanion tank push a lot of water out each time the connection at the water heater is undone for repairs?

Also, can the expansion tank be anywhere in the plumbing on the cold line or should it be as close to the water heater as possible?  I would guess it wouldn't matter.

Brian.

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 Posted: Mon Jan 2nd, 2012 02:04 pm
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LazyDevil
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Brian:

Good questions, and I'll reply in reverse order.

Since the pressure in a plumbing system acts on the whole system, an expansion tank could be placed nearly anywhere in the house and its protective benefit would still be felt. With that said, I think there are logical limits. Tank manufacturers usually want a few feet of distance between the water heater and their tank to protect the rubber bladder in the tank. As the water is heated and expands, some very hot water might expand back into the cold line and would prematurely age the bladder causing it to lose flexibility. Also, plumbing the expansion tank too close might hinder the service requirements of the water heater. In an ideal situation, there should be space all around the water heater to allow cleaning, leak inspection, and serving of the anode(s), flue and/or wiring.

Too far away might hide the tank from the attention of future homeowoners. The expansion tank needs inspection and probable service also. I think you are wise to put a ball valve in the cold line immediately before the expansion tank and water heater. This valve would isolate the two and allow their service without disrupting the rest of the cold water system.

The expansion tank should be pressurized (without water in the system) to the same value as the house's water pressure. This ensures that water would only flow into the tank when the system pressure EXCEEDS the normal pressure level; and would immediately flow back out when any water is drawn from the system. That means that in a "water in use" condition, little or no water would be present in the expansion tank; and in a "static system" condition, only the pressure induced expansion amount would flow into the tank's bladder.

Your installation should allow access to the Schrader air on the expansion tank for air pressure measurement and service. I like to install an expansion tank as in this post:

http://www.thetankatwaterheaterrescue.com/forums/forum3/3069.html

Of course, no situation is ideal. Space is often limited and the benefits of an expansion tank outweigh the extra work of having to shoe-horn one into a crowded mechanical room.

Please excuse the long post, but I think that after the corrosion fighting effects of a properly maintained anode system, proper pressure control is the second best way to prolong the life of a water heater. The added safety and reduced wear on other plumbing system components are just icing on the expansion tank cake!

Good luck.
Chuck

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 Posted: Tue Jan 3rd, 2012 05:29 am
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Realmacaw
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Chuck,

Thank you for your reply.  Your article and picture on expansion tank installation is the best I have ever seen.  It is better than the instructions expansion tank manufacturers provide.

Brian. 

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 Posted: Sun Jan 29th, 2012 09:36 am
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KULTULZ
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LazyDevil wrote: Your installation should allow access to the Schrader air on the expansion tank for air pressure measurement and service. I like to install an expansion tank as in this post:

http://www.thetankatwaterheaterrescue.com/forums/forum3/3069.html

Chuck


Is the tank mounting hardware shown in the illustration available as a kit or is just something that was devised on the job site?

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 Posted: Sun Jan 29th, 2012 05:00 pm
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eleent
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Hello:  The mounting hardware looks like off the shelf parts, (hose clamps, angle brackets, bolts).  It even has adjustability built in.  Nice :cool:

Yours,  Larry

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 Posted: Sun Jan 29th, 2012 08:31 pm
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LazyDevil
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Larry is right, it's all of-the-shelf hardware items. And he identified all the parts.

I used two hose clamps joined together because they were cheaper than one long one. The clamps circle the tank just below the central weld. Small adhesive rubber feet attached at the four corners of tank brackets do two things, they let the bracket ride over the weld and they act as contact points between the round tank and the flat bracket face.  Some heavy duty angle brackets are screwed into the wall. And as Larry spotted, two long machine screws hang the tank with room to "fine tune" the height.

Chuck

Last edited on Mon Jan 30th, 2012 04:16 am by LazyDevil

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 Posted: Mon Jan 30th, 2012 12:39 am
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KULTULZ
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;)

Cheap & efficient. Once new a girl in Baltimore like that... :P

 

THANX!

 

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 Posted: Mon Jan 30th, 2012 02:07 am
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Ej
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And you didn't marry her?????????????????????

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 Posted: Mon Jan 30th, 2012 11:21 am
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KULTULZ
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Ej wrote:

And you didn't marry her?????????????????????
My wife (at the time) had a little trouble accepting her... :X

...it was a real shame too...

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