I just replaced a leaking float vent with a Watts FV-M1 automatic float vent. It screws in the heat piping just above the water circulator. According to the instructions, after screwing it in you are supposed to back off the vent screw 2 turns for proper venting. But when I do this water comes out very slowly. Is there a problem with this vent, or can I keep the screw tightened to stop the water from leaking?
thanks.

 

When you say "screw" are you talking about the thing that looks like the cap on a tire valve on yer car ? If you screw that down, then the water will stop coming out, but any air in the system will be trapped too. Kinda defeats the purpose of an automatic air vent!

There's a float inside that can. When there's air in the system and it goes into that can, the float sinks, opens the little valve on top. Pressure in your system pushes the air out the vent. When the air goes out the top, water goes in water goes in at the bottom, and the float is supposed to go back up and close that little valve.

Sounds like the air valve isn't closing properly. It could be a bad valve I suppose, or maybe a piece of crud got under the valve stem. You could try flushing it out. If the system is HOT, you could get HOT water coming out, so do this with the system COOL!!! or exercise extreme caution.

You should be able to wrap a rag around the valve and/or put a bucket under the vent. If you push that little tire valve on top down with your finger, you should be able to open it manually. Hold it down for a second or two and let the water flow a bit to flush out any debris. Keep in mind that if there is a lot of debris in the water it could get worse. Lightly tap the little valve with your finger to dislodge the crud.

What is the pressure in your system ?

You can screw that cap down, and still run the system, but any air in the pipes will still be gurgling.


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Thanks for the reply.
The New Watts vent I installed had a plastic pin that unscrews to let the air out. I didn't like the idea of a plastic screw knob when I bought it so I also bought a Maid O Mist brand #67 with a metal vent valve similar to a tire valve.
I replaced the new Watts with the Maid O Mist and after a few minutes with the boiler running the water has stopped completely. The Maid O Mist is only rated for 50 PSI but my boiler is always between 20 to 40 psi max.

 

Your boiler should never see 40#. Rare is the system which actually needs 20#. If the boiler is getting to 40# & the relief valve is not opening, you need to replace the relief valve NOW. Residential relief valves should be fully open at 30#. All of this presumes the gauge is reading properly.

 

How many floors are you heating ?