Delta diverter

I have an anti scald single lever shower faucet. when I turn it on water comes out the tub spout and the shower spout. when I push the diverter in it stops the tub spout. how do I stop water from coming out the shower spout until I push the diverter in?

Is this a new install? Did it ever work right?

Is there a separate diverter valve? If so, it may need service.

If not, the likely problem is that you used either CPVC or PEX piping to connect the spout. This has a smaller ID and creates enough backpressure to force some water out the showerhead. Otherwise, there's something partially clogging the path to the spout.

it is a Delta faucet and the diverter valve is part of the main unit, but has a push in stem. this has been going on since it was new and I have just put up with it. it is an all copper install.

Somebody didn't pay attention to proper distances between the spout and the showerhead or, the spout is plumbed with a restriction.

Below is the old non-balanced valve. I don't see a anit-scald with the push in diverter listed.