installing an expansion tank

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Kskier

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I am putting in some new plumbing, and I have to put an expansion tank in. My questions are do I need one for my hot water tank, and the main water supply, or just my main water supply? Where do I mount it, right after the water meter? If I need one for the hot water tank as well, do I mount it on the hot side of the tank, or on the cold inlet? I believe the correct way to mount it is vertical, and just with a tee off of the main line? Do they come with air in them, or do I need to put air into it? Thank you for your help.
 

Cass

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First things first...do you have a pressure reducing valve or a check valve on the water line where it comes in the house...
 

hj

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tank

You have told us nothing which would indicate you even need an expansion tank. If not, then do not install one, because it will serve absolutely no purpose.
 

Jadnashua

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Some codes require them, regardless of a closed system or not. SO, assuming you are going to install one, you should only need one (a boiler would require its own, if that applies). It should go on the cold side of the WH after the shutoff to the WH (so it can take the pressure from the WH). Watts is one manufacturer...if you check their website, they have some diagrams. You can mount them any orientation, but keep in mind when they fail, they'll fill up with water. This also means that it must be well supported. They come pre-charged to about 40#, but you should adjust it before installation to at or slightly below the 'normal' pressure to the house. Keep in mind that this often changes during any 24-hour period as overall system usage changes.
 

Kskier

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Local code says any time you put a new hot water tank, or any other plumbing you need a expansion tank. I am not going to have this work inspected, but I was just wondering the right way to put one in. And yes, I do have a back flow perventer right after water meter.
 

Gary Swart

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The backflow preventer creates a closed system. What that means is, the water expansion can not be absorbed by the city water main and will cause a pressure rise in you water heater. You do have to know what your water pressure is to be able to set the expansion tank. A pressure gauge can be found at any hardware store for around $15. The tank is installed in the water supply line prior to the water heater. You install a tee in the water line then the mounting adapter to the tee. The tank can be mount in almost any position, but it must be very well supported. The tank has a air valve just like a bicycle or car and pressure is matched to you house pressure by adjusting air pressure in the tank. Watts recommends the use of a hand pump rather than a compressor for this because since the tank is relatively small, only a small volume of air will change the pressure a great amount and a compressor could easily burst the bladder in the tank if too much air was added. Not getting this inspected won't win too many happy faces on this forum. Code inspections are done for health and safety reasons, not to create bothersome roadblocks for the homeowner.
 

Cass

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If you have a back flow preventer they are normaly only required on sprinkler systems...not incoming water from the street...are you sure it is a back flow preventer and is it in line between the water supply coming in from the street and the heater or is it on a line heading out to your lawn....
 

SewerRatz

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There are some towns here in Illinois that have eather a RPZ or a double check assambly installed roght after the meter. Also many of the localaities requier an expansion tank installed on the water heater on any new contruction, and water heater replacments.

To answer your question, jadnashua told you how it is. You install it right after the cold water shut off to your water heater. Here is a picture, it should be properly suppurted though.
dscn0647s.jpg
 

Gary Swart

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As pointed out, that tank should be supported. If (when) the bladder fails, the tank will fill with water and that's a lot of weight to be supported by just the 3/4" pipe.
 

Hidden 1

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Hi ,I just installed a tank also and made a shelf off the wall for supporting the tank, a good heavy duty "L" bracket/board,into stud, works great for shelf .
I also set the air pressure about 3 lbs under the main line pressure to the water heater-mine is at 55 now.I also have a check valve at meter and regulator in main line entrance.
Hope it works good for you also.
 

Cass

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He may have a check valve which he is calling a backflow preventer, which it is in fact.


Why is a check valve called a check valve and not a back flow preventer...
 
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