I just built a guest house myself. Everything is new, including the pipes. With no cartridge installed, and the stops open far as they go (~½” of threads showing), I get ~8 GPM flow out of the Delta rough-in valve body (R10000-UNWS).
I’ve tried 3 cartridges (w/3/4" x 12" L brass nipple from the valve body to spout drop-ear) and all badly reduce flow from the tub spout (i.e. showerhead flow restrictors are irrelevant here).
- (RP46463) reduces it to 1.9 GPM.
- (same model) reduces it to 2.3 GPM.
- (RP47201, higher flow) reduces it to ~3.4 GPM.
I’ve never installed a Delta cartridge before, but it seems straightforward, what could I be missing?
