saddle valve cap not fitting
That saddle valve discharge is not 1/4&quot; pipe thread but instead is a 1/4&quot; OD compression fitting. If you want to cap that fitting you need to purchase a cap for the 1/4&quot; OD compression fitting. One thing to remember, not only can the valve leak but the rubber washer that seals the saddle to copper tubing will harden with time and could also fail. I hated saddle valves as a cheap install and instead used a &quot;fitting by 1/4&quot; pipe bushing&quot; to make the connection or solder in a ball valve in standard copper and reduce it's discharge to 1/4&quot; OD copper. my 2 cents