frustrating shower clog

I have some sort of clog between my shower faucets and shower head. This is a separate hot and cold Delta faucet--no bath. I have removed the handles and valves and flushed from the source--plenty of pressure, no clogs. And of course I've taken off the shower head.
I have taken a garden hose and attached it to the threads at the shower head, taken off the faucet handles and valves, and reversed flushed into the shower. No dirt comes out. But the pressure improves dramatically right away. However, within a week or so the pressure starts diminishing again so that in a month or two the pressure is very poor. Then, I've flushed it again...and again it is good for a week or two but then starts to diminish.
So, I'm assuming I have some sort of moving crud between the valves and the head. Any ideas how I can get this out permanently?
Thanks,
Michael
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MNP wrote:

This could happen if say a chunk of rubber (washer or old Delta seat) got stuck in the riser or the riser outlet on the shower control. You might try running a snake down the riser. I'm thinking of the 1/4" coiled spring type you can get in the "snake-in-a-drum" drain cleaner.
Jim
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MNP wrote:

Generally, I don't find fixing this sort of thing to be economical. Once a faucet system fails, I'll just go in and replace the valve body. If I were in your position, I would replace the riser and showerhead also. Takes an hour or so and usually less than a hundred USD.
Greg
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