Toilets, Sinks, Showers, Tubs and Disposals - Shower Diverter issue

I've searched everywhere but have not come across this problem anywhere else. I just installed a new (Moen I believe) shower system in my brothers bathroom. I've installed these before without incedent but this one's driving me crazy. Single handle hot cold valve with a shower spout and a tub spout and diverter on the end of the tub spout that you pull up to divert water to the shower head. From the first time I turned the water on with the diverter in the tub or off position, water comes out both the shower head and the tub spout. When I pull the diverter out completely, it correcty shuts off the water to the tub and directs it to the shower head with no leak into the tub. It's just when its in the off position that water comes out both places. Becasue this is a brand new spout/diverter, I am inclined to believe that its not a washer problem but possibly a alignment or pressure problem. Any ideas?

Did you install cpvc for a riser tube rather than copper? I believe if you read the installation instructions you will see they only approve copper for a riser tube. Then, again, the diverter may need attention. Can you tell if it is completely retracted by using a mirror? If not, removing the spout to correct it may be in order.

Thanks Larry for your response, yes I did use cpvc for the riser tube. That was what was in there before. In fact, the entire house uses pvc for water supply. I could have used copper from the manifold I guess but to be honest I didn't give it a second thought since pvc was originally there. I will get a mirror and look at the diver to check retraction tonight. Thanks for your help, I'll let you know what happens.

I didn't either, until I installed a new Delta once with a cpvc riser. It just didn't work correctly. Being a guy, I finally got the spec sheet and read it, and they definitely recommend a copper riser. Live and learn, I guess.