This isn’t the TPR with corrosion all over it. What is it?
Thanks, Kent
It almost looks like a water pressure regulator.
That whole setup is encouraging me to go see what Ms Margarita is doing.
air vent
As Paul stated, and it simply needs replacing when it leaks.
I’ve never seen a boiler with 18 burners.
How big is that log cabin?
Hi all,
tempering valve
hard to see with all the corrosion
Carla
Carla,
It’s definitely a Float-type Air Vent.
This vent is installed at the high point of piping loops as well as the top of tanks, boilers, or air scoops to allow air to be automatically vented from the system. Internally, they consist of a float-operated valve within a small cylindrical chamber. As air collects within this chamber the internal float drops and opens the air valve. Assuming the pressure in the system at the location of the air vent is higher than atmospheric pressure, the accumulated air is forced out. As the air leaves, the water level in the chamber rises, lifting the float and closing the air valve.
Here’s a TACO version…
http://www.taco-hvac.com/en/products.html?current_category=87
Just got into this thread and had an answer all ready to go–then I read the answers already posted…and David wins…it is a stand vent used to remove air in the water automatically.
Ever notice the water in a clear glass when you fill it with hot water??
The fog in the water is air that has “been boiled” out of the water when heated. That’s what collects in the vent and is removed.
Supr-simple explanation so that even I can understand it.
Air vent
I am with Paul and in the same boat as Jay. I knew the answer but was a dollar short and a day late, or is that a day late and a dollar short. Now I am confused, RR, does Ms Margarita have one left, I think I need one. 
Marcel
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here’s a couple pics of what one looks like new. the cap should remain on at all times, but only on 1 or 2 turns. it has holes in it to allow the air to escape when it needs to. the float keeps the needle valve shut and when it gets air in it, the float sinks and allows the air to escape.
just an F.Y.I for those who don’t know, TACO is pronounced (tay-coe) not (ta-coe, like the food). just don’t want anyone else to sound stupid like i did before i was corrected many years ago.:mrgreen:
Air vent
Darn.
And I was thinking how good a margarita would be with the “ta-coe, like the food.” :mrgreen:
no prob. RR just scroll up 2 posts, Dave V has 2, i’ll bet he’ll share with you.
P.S. this is now page 2, go to page one first.
Air vent ocurred to me originally but didn’t want to trust to memory, thanks all.
10.000 sq. ft. log home, hot water baseboard heating, great big hot water storage tank. It was hard to get the boiler to fire with all that hot water stored in the tank.
Kent