I've had really shitty water pressure for a couple weeks, starting on a morning where it was almost a trickle but came back to adequate in time for my shower. It seemed like what happens when the town pumps lose power and we're left with just water tower height to drive flow, except we didn't have a loss of power at the time. It continued to be crappy, but adequate and I thought that the water department must be having some kind of trouble.
Until yesterday I came home from work and it was back to a trickle - like ten minutes to fill a 2 gal toilet trickle. I asked my neighbors, finally, and none had a problem. Well, crap that means it's something in my house. So I decide to check my whole house filter as an obvious first step. I hadn't checked it before because it was only three months old, which is half their typical life at our usage, and all signs pointed toward a supply problem.
Obviously it was clogged too hell. The whole thing was a rusty mess and clogged to the point of almost blocking flow. That's never happened before in all the 18 years we've lived in this house. The water in this town has always been hard as nails with 600 ppm Ca and mild rust, but it's been especially bad recently. My work is in the same town and doesn't treat water the way I do at home. It's not been unusual to have yellow water in the toilets this winter.