Selecting a Moentrol rough-in valve
Moen's Moentrol rough-in tub and shower faucet valves balance incoming hot and cold water pressure to compensate for fluctuations in water flow. Balancing the water flow keeps shower temperatures constant and comfortable, within ±3°F (1°C) of the original temperature, despite other demands such as flushing the toilet or starting the dishwasher. Moentrol ® tub and shower valves all feature pressure-balancing. Moentrol valves also feature temperature memory - when shutting-off the faucet, the handle stays in the exact temperature position you set during use. The next time you turn-on the faucet, within a few seconds, the water temperature reaches your last temperature setting. Another feature of Moentrol rough-in valves is Volume Control - Controls the water flow rate so you get the amount of water you want at the temperature you want.
Model 3520 is 1/2" CC (1/2" Copper Pipe x 1/2" Copper Pipe) and should be used if you are soldering all joints including joints that connect to the shower valve, in most cases you are running copper pipe throughout your home.
Model 3510 is 1/2" IPS (1/2" Threaded Iron Pipe x 1/2" Threaded Iron Pipe) and should be used if you have pipe thread connections to connect to your shower valve. This could mean you are using galvanized pipe (not typical in most plumbing installations) or you are using copper pipe with a MIP (male iron pipe) adapter.
Model 3570 is the same as model 3520 except that it comes with integral check stops which allow you to service the valve without shutting off water to your entire house. Basically you can replace parts on this unit without turning off the water to your house.
Model 3330, for use with Moentrol Vertical Spa Sets, is 1/2" CC (1/2" Copper Pipe x 1/2" Copper Pipe) and is for use with copper pipe installations. This valve includes integral check stops that allow the valve to be serviced without shutting off water to the entire house.
Model 3320 is that same as model 3330 except that is has iron pipe connections 1/2" IPS (1/2" Threaded Iron Pipe x 1/2" Threaded Iron Pipe).