How To...Plumb Expansion Tank to Mobile Home Water Heater with PEX

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kailor

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I have plumbed my electric water heater (40 gal.) in a mobile home with PEX. Inspector says I must add expansion tank. Cold inlet is near bottom. Most available space is above the water heater. How can I do this while staying all PEX? Thanks in advance.
 

Jadnashua

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The water under pressure doesn't really care how you run it within reason. Find a place where you can install a T, and run the T out to the tank wherever you want it and it fits. The T should be between the WH and the shutoff...IOW, there should not be a way to isolate the expansion tank from the WH with a valve so there's always a place for the expanded water to go.
 

kailor

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Thanks. I guess I should also have asked if I need to build a shelf to hold expansion tank since I'm using PEX. Is the idea to simply add the tank and secure it such that it won't kink the pipe?
 

Jadnashua

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Eventually, the expansion tank WILL fail, and at that time, will fill up with water. That would become quite heavy, and as a result, yes, it must be supported and not just hanging from the PEX. They usually last a fair amount of time, but there is no guarantee.
 

John Gayewski

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They have been requiring us to use the mounting bracket designed for them. You just screw it to the wall and use the hose clamps that come with it to attach it to the bracket.
 

Sedin26

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Here's a pic of mine. We moved into our 1994 mobile in 2017 and after a bath and waiting a while, the water would come flying out when first turned on. I didn't check the pressure but knew it was too much, particularly since there was still some Poly-B.

We had a small closet for the WH and a modern, standard sized tank wouldn't fit in without cutting things apart so I got a plumber to source a 65 gallon Bradford White that's thinner than standard. Replaced PRV under the house and also the main line from the shutoff into the house, as well as any of the old Poly-B we could get at. You can't tell from the picture but it was quite an operation getting a tank this size in there, though well worth it for the extra capacity. We also added a pan underneath and had it plumbed to drain under the house. I later added one of those Moen water sensors that should let us know if there's a leak into the pan - it seems to work well every time I test it.

On to your specific question, you can see the expansion tank in front, coming off a T on the cold water line and strapped to a bracket they screwed into a board. The space is smaller than it looks in the picture and I was surprised it fit but it does. It also could have been placed up above the heater, though that would have been more difficult.

IMG_4555.jpg
 
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