Threaded vs. Slip-fit valves

A note about "threaded" and "slip fit" valves:
"Threaded" valves have an inside (female) thread connection and are designed to be connected to a male adapter, which is in turn glued to a pipe. "Slip fit" valves are installed by glueing them directly on the end of the pipe. Most people think they should get a threaded valve, because they sense that would be easier to replace if it should ever be necessary, but we believe that is a wrong conclusion and we almost always recommend slip-fit valves for the following reasons:

• The valve body, which is the only part that is different between a slip fit or a threaded valve, virtually never needs to be replaced. Virtually all repairs are accomplished best by leaving the valve body in place and replacing either the solenoid, diaphragm, or the entire upper portion of the valve.
• To uninstall a threaded valve you're going to have to cut a pipe before you can unscrew the valve anyway.
• Leaks are common in threaded joints unless they are taped and installed very carefully- slip-fit valves are much less likely to leak after installation. Screwing the threaded adapter in real tight to stop leaks is not recommended because...
• If you screw the adapter in real tight, you'll put so much stress on the valve body it can crack in the next couple of years, and you'll have to replace the whole valve.
• To install a slip fit valve you need to glue a pipe into both ends of the valve. To install a threaded valve you need to install the threaded adapters, then glue a pipe into both ends of the valve. It's therefore easier to install a slip-fit valve.

If you are installing a valve in a system with polyethylene lateral lines, you may want to get a threaded valve because you will need to screw in a barbed adapter into the outlet anyway, but we believe even in that case there is no disadvantage to using a slip fit valve. You'll still gain the advantages of a slip fit valve on the inlet side where it is connected to the PVC main line, and that is the most critical connection to the valve.

Unless your application specifically requires installing a threaded valve, we recommend a slip-fit valve.

[Close this window]