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jackwashere 05-16-2013 09:27 PM

expansion tanks - why no stand?
I'm just trying to understand things. How come all the expansion tanks I see on the market install upside-down and hanging in the air. I'm thinking that thing must get pretty heavy being partially filled with water and all. It will put a strain on the pipes. Wouldn't it be smarter and easier if the thing was on a stand? Only the bigger tanks (7 gallon+) come with a stand. Why?

Also while we're on the subject. On youtube when I searched expansion tank I found several installation videos. One of them was from HomeAdditionPlus and features a green tank. He goes on to say how you can test the expansion tank by checking if the top is warm and the bottom cold. Wait a second! I thought expansion tanks are supposed to be installed on the cold water side not the hot water side. The video claims to be about water heater expansion tanks not the other type. Did this guy install it on the hot water side? Go figure! Another video posted by jthet2001 shows a homemade contraption to hold the water tank up. Seems like alot of work. There are videos advertising the hydroclaw which holds the expansion tank in place. No doubt it costs alot. Better to just pay the extra bucks and get a 7 gallon tank with a stand.

oh'mike 05-16-2013 09:41 PM

If the pipes are sound and secured properly, the weight does not hurt anything----

Hang around here for a while---you will see and hear many strange plumbing stories---
As to Youtube videos? More bad than good---I've seen some major mistakes,proudly displayed ,with directions ---so you,too ,can have a dangerous non code complainant mess of your own!

joeplumber85 05-16-2013 09:45 PM

As long as your piping is properly supported then it should be fine to hold an expansion tank of limited size.

On 99% of domestic hot water set-ups it doesn't matter where you put the expansion tank. Some guys say hot side, some guys say cold side, but the tanks are generally rated for +180* temperatures and often the same tank being installed on the cold side of your 40 Gallon HWT is also being installed on the 180* supply piping of your neighbours boiler.

I personally install them on the cold side, downstream of the shut-off as it's just habit for me but if there was no room I would have no concerns about putting it on the hot side.

Ghostmaker 05-16-2013 09:49 PM

The tank actually doesn't fill with water unless they fail. You should strap them up with band iron so the you do not break the pipe if that happens, The other detail is your suppose to pressurize the bladder in the tank to the same pressure as the incoming water supply. You will find a snifter for air under the end cap.

Alan 05-16-2013 10:30 PM

There's an entire thread dedicated to this topic. Use the search function.

Alan 05-16-2013 10:33 PM

AND..... since I know you're probably going to get pissed at my remark like you always seem to do, I typed 3 words into the search bar and found it for you.

TheEplumber 05-16-2013 11:34 PM

199 Attachment(s)
Put it on the cold side, put it on the hot side. Does it really matter? No, but cold side is done most often.
I used on of these a couple weeks ago- pretty darn slick and gets the tank out of the way-

AllanJ 05-17-2013 08:32 AM

Before they invented bladders for expansion tanks, the tanks had to be mounted above the pipe they were attached to so the water would not accumulate permanently inside and the air would not be lost quickly.

The expansion tank for a water heater will work from anywhere in the water system provided that there is no closed valve or check valve between it and the water heater. The pressure tank for a well pump can actually serve as the expansion tank for the water heater even though the air cushion has a different pressure setting. However most inspectors prefer that the expansion tank be above the water heater so they don't have to go looking for it.

An expansion tank really should have extra support just in case the bladder fails and the tank should fill with water.

raylo32 05-17-2013 09:52 AM

I have a 5-gal expansion tank connected to my cold line hanging from the pipe (copper) for many years. The pipe is dead ended just past the tank and the bitter end rests and is clamped to the top of the 2x4 header. A year or so ago I ran a piece of galvanized strapping going onto the air valve on the bottom of the tank and then nailed the ends of the strap to the 2x4 header. Didn't really need it but it looks more secure.

whirlpool 05-17-2013 10:49 AM


Originally Posted by Alan (Post 1180935)
AND..... since I know you're probably going to get pissed at my remark like you always seem to do, I typed 3 words into the search bar and found it for you.

AH but for the layman... what three words? :)

It is the old story. A person gets in the plumber/electrician/whomever/ to do a job. They complain "why is the bill so high, you must break it down for me" and the response is "5c for the washer and $99.95 for the knowledge of installing it"

Frankly, your second post was far easier on all, especially as you might be dealing with someone overseas who uses the word "cylinder" instead of "tank"...

jackwashere 05-17-2013 01:46 PM


Originally Posted by whirlpool (Post 1181163)
AH but for the layman... what three words? :)

Those three words would be "when it works".

As a matter of course I use search when it works. Search for "expansion tank" on this forum and everything related to plumbing comes up. Gee that's funny, I could have just looked at the plumbing forum without search and gotten the same results!

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