# Service valves



## plumber101 (Jun 28, 2009)

What do you use to seal the cap on a sevice valve?


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## Yuri (May 28, 2009)

If it is a brass cap on a brass valve it should have a knife edge on the valve and 99.5 % of the time if tightened carefully they will mate and seal. The rest of the time I use nylog:http://www.acsource.com/index.asp?PageAction=VIEWPROD&ProdID=185

It never hardens and you wind it around like a string on the threads.


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## mechanicalDvr (Jun 25, 2009)

I find more often than not they seal well when they are clean. I have used the nylog gel when there seems to be an issue.


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## henny (Jul 6, 2009)

plumber101 said:


> What do you use to seal the cap on a sevice valve?


The brass caps seal quite well when done correctly. (clean cap, finger tight + one flat worth of extra turn)


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## supertek65 (Oct 1, 2009)

refrigerant oil although it is hyroscopic and can eventually pick up some moisture


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## user865 (Mar 14, 2010)

I'm always finding trace leaks under service valve caps. I used to always seal the threads with leak lock and tighten 1/12th of a turn tight. Now I notice alot of manufacturers are using a rubber gasket, under the brass caps, to prevent the leaks.


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