On 11/27/2015 9:28 AM, Oren wrote:
On Thu, 26 Nov 2015 18:46:42 -0700, Don Y
wrote:

On 11/24/2015 12:31 PM, Oren wrote:
On Tue, 24 Nov 2015 12:21:12 -0700, Don Y
wrote:

How/why do you use these on a swimming pool or solar (water heater?)?

There is an auto / positive drain (2 Inch dia.) at the peak of the
solar panel. It ensures the panel drains completely during winter.

So, it acts as an air *inlet*, not a water *outlet*?

Yes.

OK. In my case, the valve acts as a drain through which the water exits
the vessel (pipe)

It
does freeze hard some years here in the desert. The panel water drains
back into the pool. Not for pool draining.

Solar POOL heater?

Ummm. I mean panels.

As in "Not for panel draining", yes, I understood. But, the fluid
circulating through the panels is "pool water" so the *panel* can drain
back into the *pool*.

(In my case, the *pipe* is draining into the valve vault/soil)

I have http://www.heliocol.com/ brand.

Many folks, here, just put a gazillion feet of coiled black plastic/nylon
pipe on the roof and run the water through that.

OTOH, covering the water surface (esp at night to *retain* any heat)
and letting it soak up the Sun's rays will easily raise the water
temperature a fair bit above ambient (considering it is over 100F
more than 60 days each year, that's considerable).