Automatic Air Vent Valves

invisible-man · Aug 15, 2011

Hi everyone,

I need to replace the automatic air vent valves in my domestic hydronic heating system and was going to use the Watts FV-4M1 valves.....I noticed that there are 1/8" and 1/4" sizes, does this relate to the thread size, as I do not know which ones to order.....is there a common size in a domestic system?

Many thanks, Martin

Cwhyu2 · Aug 15, 2011

Yes it is the thread size.

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invisible-man · Aug 15, 2011

Thanks cwhyu2.......do you know if one size is more common than the other?

Cwhyu2 · Aug 15, 2011

1/8 is the most common that I have worked with but there are other factors as in is it metric or iron pipe size,and is it base board or iron radiators.

invisible-man · Aug 15, 2011

cwhyu2 said:
1/8 is the most common that I have worked with but there are other factors as in is it metric or iron pipe size,and is it base board or iron radiators.

It is my home in Michigan US and has baseboard heating with a WEIL McLEIN Gold series 4 boiler......

BobL43 · Aug 15, 2011

invisible-man said:
It is my home in Michigan US and has baseboard heating with a WEIL McLEIN Gold series 4 boiler......

Without being able to see it from here, it would be easier to say which size you have if you can measure the actual diameter of the threaded part of the air bleeder. What you actually measure is not what the iron pipe size is called, but it will give us an idea of which one it is, if it an American thread. for instance, the 1/8 pipe size actually measures out at "3/8" inch, and the 1/4 inch pipe measuures just about "1/2" inch in outside diameters. (Not measured with a caliper, but a tape measure or steel rule).

invisible-man · Aug 15, 2011

BobL43 said:
Without being able to see it from here, it would be easier to say which size you have if you can measure the actual diameter of the threaded part of the air bleeder. What you actually measure is not what the iron pipe size is called, but it will give us an idea of which one it is, if it an American thread. for instance, the 1/8 pipe size actually measures out at "3/8" inch, and the 1/4 inch pipe measuures just about "1/2" inch in outside diameters. (Not measured with a caliper, but a tape measure or steel rule).

Thanks

Problem is that I am in the UK so cannot measure, and wanted to order parts before arriving in the US.....perhaps I can ask a neighbor to measure the outside diameter of the existing ones!

hj · Aug 16, 2011

Basseboard would usually have 1/8" vents, and cast iron radiators 1/4".

invisible-man · Aug 16, 2011

hj said:
Basseboard would usually have 1/8" vents, and cast iron radiators 1/4".

Thanks for that, 1/8 does seem to be the general opinion, I do seem to remember them having quite a fine thread!

Automatic Air Vent Valves

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