I have the same problem !!!!! Delta told me they have seen this problem before. Poor engineering if you ask me. New cartridge does the same thing. Should have bought a Moen.Back in February, planning our bathroom remodel and shopping for advice and recommendations for a new valve, advised to go with Delta. Didn't work out to well , my tale of woe follows:
As you can see we're several months down the road on this one, finished our remodel about a month ago. I did choose the Delta Universal valve w/ScrewStops and added a 17430 trim kit (the 17 series controls volume with one lever and temperature with another). Looks great, installation was a breeze, except...
I've had a problem with this setup since installation. The lever for volume has an approximate "arc" of turn of about 90 degrees from closed shut to full open. The first drop of water doesn't come out of this thing until I've turned the lever through a bit more than 45 degrees of the arc, then water continues to increase in volume until I hit the stop at about 90 degrees of arc.
That means that I'm moving the lever a bit more than halfway before anything starts to happen! The amount of volume at full on is "sufficient", but not very great. It's difficult to quantify that, except to say it's certainly less than the old valve/trim gave us (from the 60's: two separate handles, etc). You sorta feel that if only the lever could continue to turn an additional 45 degrees you'd get all the volume you could handle <g>...
Fooled with it a bit to see what I could have done wrong , but everything looked OK. I called Delta. Their response was to ask me to pull the cartridge and shake it, see it "rattled" to make sure it was not locked up. Did that, it rattled as it is supposed to.
As [bad] luck would have it, after removing the cartridge to check it out, a cover and spring from the Cartridge Adapter Assembly popped off the adapter and went down the drain, no luck in finding it. Sooo, called Delta back, they very nicely agreed to send a replacement Cartridge Adapter Assembly, a small plastic part with some O-rings, springs, covers, etc, which fits into the valve body outlets. Took about 2 weeks to get here.
Installed the adapter assembly, reinstalled the cartridge and trim, tested and still the same as first reported: no water comes out of the spout until about halfway through the turn of the lever. I called Delta to tell them we were back in business, the cartridge did rattle, and the problem was the same as intially reported. They very nicely agreed to send a replacement 17 Series cartridge in case the cartrige I had was bad, and it also took about 2 weeks to get here. They are very kind, willing, helpful folks, and I appreciate all they've done so far.
The cartridge arrived earlier this week and the first chance I had to play with it was yesterday. Removed the cartridge (and the adapter assembly, because they had also sent a new one of those with the cartridge), reinstalled the whole deal, no luck, same thing, bit more than halfway through the turn before any water.
Called Delta this morning, reported my results, placed on hold while they checked things out. They come back on the line and tell me that it is "normal" for the lever to have that much "drag" (their term for this) on it.
So we're done. Wish to heck I'd never chosen Delta, and I sure won't chose them for the 2nd bathroom that starts next month. This was our "dream" bath, a complete down to the studs remodel, new everything and we've a decidedly crummy bath/shower experience.
Just in case anyone here has some insight into what is happening, or any recommendations, I'd appreciate any and all comments that might lead to some better outcome