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When are expansion tanks required?


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Originally posted by chicago

I just did a condo with 50 gallon tank that had a 4.4 gallon expansion tank.

From what I gather these are to keep thermal expansion from tripping the TPR valve.

Does anyone know how it is determined when these are required.

Generally, you use one of those things when the water service includes a pressure reducing valve. Particularly if the PRV lacks a bypass to allow excess pressure back to the street side.

- Jim Katen, Oregon

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Yes... read the attached PDF.

It says cold side which is why I said, thanks for the heart attack.

It is easy to confuse with hot water furnace expansion tanks.

Glad some one gave it a thought though as They are not that common that I have seen.As far as the hot water tanks are concerned.

Steve I see you posted same time.

Is it boilers or furnaces.I think of boilers as steam.Hot water as furnace.

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Yeah.. but the hot water never boils.

Your right though.

Hot Water (Hydronic) Heat

Water is heated in boiler, usually to between 160 and 180 degrees Fahrenheit. Pumps circulate the hot water through pipes in the building. This heated water warms radiators placed in the rooms. These radiators, in turn, warm the air in the room.

In some homes, pipes are buried in the concrete slab. This is type of system is called radiant heat.

Many people prefer (hydronic) hot water heat, because the radiators are small, the system typically quiet, and it can be easily divided into multiple zones. Hot water heat has made steam heat obsolete in homes and smaller buildings.

Cherry picked from here.


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Chicago now requires a tank on any new construction water heater install, and they also want to see a pan under the water heater.

The city (read union) also wants a pressure pump on any water inlet <1 1/2".

Of course, this being Chicago, approx. half the goofballs working don't know they're supposed to be doing this.

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My friend, do not EVER feel dumb about not knowing some aspect of the Chicago building/plumbing code.

This town is one goofy code stew; theres stuff @ the buildings dept., lots of stuff over @ DCAP (Dept. of Construction & Permits), and every mechanical trade has their own stuff, w/an amazing amount of it scattered over multiple documents.

I think they do it this way intentionally so no one can know anything.

Steve Hier (a great friend & inspector) and I make calls to various officials from time to time to figure this stuff out. Honestly, I'd have to check w/the guy in City Hall to find out when this was enacted, but it's been in place for a while. The pan ordinance has been in place for years, and it's only recently that folks started installing them.

Don't be surprised if some union plumber tells you I'm wrong; most of them are morons. (Sorry, but it's true.)

You know as well as I how inspections work in Chicago; the inspector is, first & foremost, a union brother. After that, they tend to be nephews of union officials. To top it off, there are few inspections, and they tend to be mere reviews of fees & paperwork, not actual inspections. Inspections do happen, but they are few and far between, and often politically motivated.

Harsh realities of the Big Dirty......

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Speaking about Chicago Water Heaters & Inspectors, here are a couple more interesting facts; some water heaters require vacuum breakers. If they are bottom-fed or elevated above the fixture they are servicing. Also the pans can not be plastic they have to be galv or non-corrosive metal.

Does anyone know if they are enforcing heat traps on commercial water heaters?

Now speaking of the plumbing inspectors I have experience with in the past, well I can't say much because I don't want to get subpoenaed. I will say, they rarely buy their own breakfast & lunch...

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