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Posted by Erik Dillenkofer on September 18, 2007, 6:02 pm
Without the check valve, if there's a break and pressure is lost the unit
could empty. If the unit is empty and fires up it will burn out.
> PaulS wrote:
>> Thanks for the help. I'm still confused. Mine is a tankless unit in the
>> basement and the input/output lines are on the bottom. Wouldn't the
>> water pressure in the input line before the water heater prevent the
>> water from reversing direction? Can you explain a little more?
>> Thanks,
>> Paul
>
> Paul,
>
> Please don't top post.
>
> The check valve (or as some call them; backflow preventers) are only there
> to stop what could be a problem in only certain instances.
>
> If you were gone for a month or so, the water sitting in your pipes could
> become stagnant. If there were to be a main break in a water line
> somewhere near your neighborhood, they might have to shut off the water
> supply in your area. When the water supply is shut off to YOUR main, the
> level in the main drops a bit from people turning on their water, leaks,
> etc. If the main that supplies your house is lower than any point in your
> home system, then water may flow back into the main from your home. Thus
> putting stagnant or even contaminated water into the main. Thus, the
> check valve.
>
> Miniscule chance of any problems, but it has happened.
>
>>
>>>
>>>>I have an installation guide for a tankless hot water heater. It says to
>>>
>>>put
>>>
>>>>a check valve between the water heater and water shutoff valve. Why? I
>>>>know what the valve does since I have one, but am don't see the point.
>>>
>>>Any
>>>
>>>>help would be appreciated.
>>>>Thanks,
>>>>Paul
>>>
>>>It's probably a water supply co regulation to stop any possibility of
>>>back
>>>flow into the mains causing contamination.
>>>
>>>If you have a tank the fill pipe is usually above the water level which
>>>stops back flow so no need for a valve in that case.
>
>
> --
> Robert Allison Rimshot, Inc.
> Georgetown, TX
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