Airxcel mechanical freeze valve on tankless water heater

[Kopy kat]

Although I filled my tankless water heater with antifreeze, the mechanical freeze valve did it’s thing and opened up at it’s set low temp and self-drained the unit.

The question now is do I have to replace this thermo-plastic valve, or does it close itself back up when the air temps rise?

I haven’t found anything about this in the owners manual, other than saying that it is there.

Anybody have an idea?

Thanks, Larry

[chuckster57]

I haven’t had any luck looking. The only thing I can say is try it, if it doesn’t leak then it must be a resetting valve.

[Kopy kat]

That’s what I’m hoping for, as it’s a thermo plastic valve, it might go back to it’s original shape. The only other reference I found was to manually shut a needle valve if there was a consistent drip...

[JRTJH]

The way I understand the system is that the frost valve is a mechanical valve and starts to open at 39F to drain water, protecting the system from freeze damage.

Since it's a "mechanical valve" it does not sense whether there is water, antifreeze or air inside it, but the "thermoplastic stem" begins to shrink when the temperature falls below 39F. As such, then it will "always" shrink when exposed to low temperatures. It will do this regardless of whether the system is winterized or not.

So, every time the trailer is exposed to temperatures below 39F, that valve will function and when the temperature rises above 39F, it will reset. The function of the needle valve is to "over-ride the valve" in the event it fails to return to "normally closed position". Otherwise, it will "open and close depending on temperature" with no impact on whether the system is in use, drained or winterized with antifreeze....

The way it's supposed to work, whether you winterize the trailer or not, if the trailer is plugged in, the water heater will sense low temperatures and turn itself on (temporarily) to keep the internal temperature above 39F. If the trailer is not plugged in, the mechanical valve will open to drain the water heater to protect itself. If the water heater is drained, nothing will come out of the valve. If the water heater is filled with antifreeze, then you'll have "pink fluid" below the valve. Once the temperature rises above 39F or if plugged in/turned on, the water heater is called to heat water, as the temperature rises, the frost valve will close.

So, whether you "winterize the water heater or not" that valve is going to open "on its own" when the temperature falls below 39F. It'll close "on its own" when the temperature rises above 39F.

If it were "my trailer" I would winterize the water heater by draining all the water out of it. I would not depend on a "mechanical device" that could break and stop working. If it should malfunction, your water heater might be damaged. Why risk the potential damage if the valve might, somehow fail ??? YMMV

[Kopy kat]

Thanks for the info. I had already used air to blow out the total water system (hot, cold) and had sucked antifreeze into the total water system...so was surprised to see the wet spot under the drain tubes the other day. And yes, we are having below freezing weather...might be easier to just head south to warmer climate???

[JRTJH]

Originally Posted by Kopy kat

Thanks for the info. I had already used air to blow out the total water system (hot, cold) and had sucked antifreeze into the total water system...so was surprised to see the wet spot under the drain tubes the other day. And yes, we are having below freezing weather...might be easier to just head south to warmer climate???

Your experience with using compressed air to "blow all the water out of the system" is the same as mine. There's ALWAYS some residual water that escaped the compressed air and remains in the system, SOMEWHERE.....

Where that residual water collects is the "million dollar question".... If it collects/condenses in a low spot that is potentially going to be damaged by frozen water expansion, then it can cause damage. If it collects in a location where the expansion will not cause damage, then there's nothing to worry about.... My concern is not if there will be residual water, I know there will be... Rather my concern is WHERE that residual water will collect. Living in northern Michigan where we get weeks/months of below zero temperatures, I always use RV antifreeze to follow the air compressor. That way, I feel comfortable that even when that water condenses in a low spot, there'll be antifreeze to prevent it that pooled water from expanding and damaging some expensive component.....

It sounds like your "extra water" pooled in the water heater and found its way to the freeze valve... At least "Like Elvis, some of that extra water has left the building"

[Kopy kat]

ChuckS...I blew out the total lines (hot and cold) clear down to the low point drains and all faucets (including the unused washer hookups)...then pumped the total system (including the tankless WH) full of antifreeze. The secondary thermoplastic non freeze valve did do it’s thing though, and emptied the antifreeze filled coils in the tankless unit. I’m feeling safe at this point as there shouldn’t be anything but antifreeze in the system. Thanks for the picture, Larry