Water Flowing to Shower Head and the Spout Simultaneously

Couple of ideas: If you don't get water at all first check to see if the shut-off valves are open. If so, close them and remove and clean the cartridge. If water comes from the spout and not the shower head, make sure the diverter (the handle on the tub spout) moves up when you pull it. If that works, remove and clean the shower head since there might be debris blocking the water flow. Without
more info this is my best guess.

One rule I live by: more parts, more problems. Sounds to me that the plumbing/valves were not insalled properly. If you hired a profesional plumber, have them fix it. I am a licensed profesional plumber and I offer a 1 year warranty on all my work. If the contractor did the work and does not hold a plumbing license, that person is still responsible and may have to suffer legal consequenses.

You need a diverter in your spout. The spout will screw off and the new one will screw on. Lift the ball while the water is running and it will divert the water to the shower.

Do you have water coming out of the tub spout and not the shower head? If so how does the water get directed to the shower head,is it by pulling up the diverter on the tub spout?If water is still coming out of the tub spout then the diverter is bad and the tub spout needs to be replaced.

Make sure the hot water is turned back on. Pressure balancing valves won't work if both cold and hot water is not on. Pull shower head off and test to see how it flows out of the shower arm. If good, clear out shower head. Whenever water is turned off for a time, and then turned back on, restricting shower heads and aerators usually get clogged. In the future, always open up a tub spout before turning water back on. This releases the air and other debris most effectively before testing other fixtures in the house.

To talk about your problem forces me to assume a few things.....If you allow the water to flow without cartridges and handles, the water must be flowing straight through the cartridge channels and out into the tub. It is not flowing through your tub spout or shower head when you test the water this way. If I'm correct, then the problem is isolated to the water mix operation. That means coming out of your spout or shower head. So now I have to ask a question. When you operate as normal (cartridges and handles installed) does your problem show up only on your shower head or does it also show up when operating out of the tub spout? If the problem is isolated to the shower head, try a head replacement. It may be partially plugged. If it's head or spout there may be something in the mixing pipe that only shifts around as pressure increases. I hope that is not your problem. It would require pulling those pipes out for inspection and most likely replacement. Nimsgame

The faucet was installed upside down.
The shower riser pipe in the wall is to short( the distance between the faucet and shower head).
One of the biggest problems is if your shower faucet was installed with Pex pipe to the tub spout. Pex pipe will restrict the flow and force the water back up and out of the shower head.
The tub spout must be piped with at least 1/2 brass pipe nipples and fittings, or 5/8 OD. copper pipe and fittings.
Hope this helps, if you further questions please let us know.

Before you do that remove shower head and see if you have flow without the head. The shower heads clog much more easily than the diverter valve

SOUNDS LIKE A RUBBER WASHER HAS FAILD , YOU NEED TO OPEN THE TAPS TO INSPECT THE WASHERS AS THEY MIGHT BE BLOCKING THE WATER FLOW .

sometimes there are orings or gaskets that get tore in assembly one of those may be bad,or if it is around the threds you might try wraping teflon tape around the thred once or twice.hope this helps