Resideo PV125S/U 1-1/4" SuperVent Air Eliminator Sweat

The PV125S is a SuperVent air eliminator from Resideo (Honeywell Home), 1 1/4 in sweat connection, 38 Cv.

Why air has to come out of a hydronic loop. Fresh fill water carries dissolved air, and heating it drives that air out of solution. What it does next is all bad: it collects at high points and blocks flow, it gasses through the circulator as noise, it puts oxygen against steel where there was none, and it turns a radiator into a cold half-radiator. A system that has to be bled every autumn is a system that is still taking air in somewhere.

An air eliminator works by slowing the water down. Inside the body the flow spreads out and loses velocity, the bubbles stop being carried along, they rise into the vent chamber, and a float valve lets them out. It runs continuously, with nothing to set and nothing to press.

Flow capacity is 38 Cv. Size the separator to the pipe it sits in, not to the boiler — an undersized body throttles the loop, and an oversized one is money spent on brass.

Sweat joints are soldered. It is the cheapest connection in parts and the one that needs the pipe dry and the flame allowed.

Put it where the water is hottest and the pressure lowest — on the supply, close to the boiler outlet. That is where air comes out of solution most readily, and catching it there keeps it from reaching the rest of the system at all.

Body is bronze, rated to 240 F maximum and 125 psi.

• Brand: Resideo (Honeywell Home)
• Manufacturer Part #: PV125S/U
• Type: Air eliminator (air separator)
• Pipe size: 1 1/4 in
• Connection: Sweat
• Flow capacity: 38 Cv
• Material: Bronze
• Maximum temperature: 240 F
• Maximum pressure: 125 psi
• Dimensions: 8.4 in high x 3.7 in wide x 2.5 in deep; Maximum diameter: 2 1/2 in
• Shipping weight: 6.0 lb
• Category: Air Separators