We bought this house 10 months ago, and for the first 2 months we had terrific water pressure in the upstairs shower/tub. Then one day, no more! The flow is now annoyingly low in pressure.

I have looked for answers to this question online and see that I should check the aerator, but I don't know that my tub/shower has one (unlike the kitchen sink, which clearly does). Am I failing to look in the right place? Is there anything else I could check?

Thanks for any input!

Single handle I'm betting. Any chance of a picture or brand/model of that valve? In all likelihood you have clogged cartridge but I need more info to get started.

It's a Moen, Model: L82691. Yes, it's a single handle. Interestingly, we changed the original fixture (circa 1964) to this one AFTER the water pressure became a problem. I was hopeful that the change would resolve the problem, but it did not.

Here is what I suggest for now. Moen provides some great tutorials on installing and removing cartridges so give this link a try. If, for some reason the cartridge can't be cleared, Moen will give your free parts for life under their wrranty. This is an exploded diagram of your Adler http://www.moen.com/shared/pdf/l82691pt.pdf it uses a 1222 cartridge. This tutorial is for another model but the basics are the same. Installation Help / Animated Tutorial - Installing the Moen 1225 / 1200 Cartridge