I've been searching this helpful site and think I have a vague answer, but as it is plumbing, and I am NOT a plumber, I will try to get more specifics.

I'll be as brief as possible.

Slow but sure, shower has become a trickle. Removed shower head and ran water, still a trickle. From what I have gathered from other posts, it sounds like I need to "Flush the valve." If so, could you confirm this, and give me step by step? (I'll list the faucet type at end of post.)

If this ISN'T the solution, any ideas?

It's a One Knobber, it says "Temptrol" in big letters, and in smaller letters says "Symmons Model A".

Also, if this helps with diagnosing this; Again tub is FINE. With water running, then switch to shower mode a la that Slide dealie, it (for the last week or so) takes like 8 seconds for water to come out of the shower.

Any help you can offer would be wonderful. (I live in New England, and just yesterday had to pay $7000 for a new Gas Furnace install. It was unexpected, as is usually the case with homeownership, and as a result REALLY can't afford a plumber at the moment.)

Thank you for ANY hep you can give me!

Capt.S

The slide dealie is the diverter. When you move the diverter does all of the water to the tub stop completely?

Saw that you replied, and I ran to check.LOL
The slightest dribble still comes out of the faucet, when the shower is on. Slight, perhaps, but in a word, No, it does not stop completely.

I thunk you had pounds and we got dollars. So 7k in pounds is what?
Symmons - Warranty
Call the symmons rep and he will walk you through this.