Expansion tank with no pressure regulator?

I looked at a friends basement water lines recently and noticed that he did n't have a water pressure regulator but he had an expansion tank above his water heater. He said the guy who installed the water heater told him he ne eded the expansion tank to meet code. I doubt there are any backflow preven tion valves unless it is built into the water meter outside.
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On 10/13/2013 11:12 PM, Davej wrote:

Many are set up that way with a bladder tank Fill valve is probably sufficient to act as backflow prevention.
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On Sunday, October 13, 2013 8:12:58 PM UTC-7, Davej wrote:

idn't have a water pressure regulator but he had an expansion tank above hi s water heater. He said the guy who installed the water heater told him he needed the expansion tank to meet code. I doubt there are any backflow prev ention valves unless it is built into the water meter outside.
The expansion tank is to prevent water hammer, has nothing to do with press ure - that is provided by the water system. The back flow preventer would be part of the water meter.
Harry K
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On 10/14/2013 12:07 AM, Harry K wrote:

You mean the water authority here has been lying to me?
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On 10/13/2013 11:12 PM, Davej wrote:

and noticed that he didn't have a water pressure regulator but he had an expansion tank above his water heater. He said the guy who installed the water heater told him he needed the expansion tank to meet code. I doubt there are any backflow prevention valves unless it is built into the water meter outside.

Did you have a question, or are you just thinking out loud?
. Christopher A. Young Learn about Jesus www.lds.org .
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On Monday, October 14, 2013 6:47:18 AM UTC-5, Stormin Mormon wrote:

My question would be whether such a system makes sense? Unless there is a backflow preventer out in the outdoor water-meter the expansion tank isn't going to do much of anything.
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On 10/14/2013 11:06 AM, Davej wrote:

Unless there is a backflow preventer out in the outdoor water-meter the expansion tank isn't going to do much of anything.

Agree. Your thought makes sense, to me.
. Christopher A. Young Learn about Jesus www.lds.org .
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wrote:

Above a domestic water heater, you are correct unless there is a check valve. My original thinking was a boiler (often used as a water heater also) where the fill valve would act as a check valve too. There it makes sense.
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On 10/13/2013 10:12 PM, Davej wrote:

Sometimes there is a check valve at the water meter to prevent back flow that could contaminate the public water supply. When the water in the water heater expands from being heated, it will leak out of the TP valve on the heater if there is no expansion tank. It really depends on the practices of the utility supplying water in your area and the plumbers will know. ^_^
TDD
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