I have a shower that has very low flow from the hot and cold water and also from the shower when you turn the valve to switch it to the shower. All of the other fixtures in the house have strong flow including the sink in the same bathroom. Unfortunately there isn't an easy way to get access behind the shower (tile on both sides of the wall). Does this sound like something that could be caused by bad cartridges? What about some kind of corrosion built up in the pipes? How can I go about diagnosing this without ripping open the walls?
If you have a shutoff valve feeding that bath or that shower, I would check:
- Is it on all the way?
- If it is, you can sometimes disassemble it in place (of course turn the house water off first). The typical valves for this application are gate valves, which can get a lot of gunk in them. Disassembly will also let you see if the problem is before or after the valve (with valve disassembled, turn on house water for a second; Did you get good flow or not?).
- If you disassemble a gate valve don't be surprised if you need a new stem seal (the seal that keeps it from leaking around the shaft).
Sometimes there is a screen in the shower head that can collect mineral deposits over time. They look kind of like white beads. Try removing the shower head and see if any more water comes out.
Remove the shower head, then try the shower. If you get full flow, replace the shower head. If you get low flow, probably there is a buildup of corrosion inside the pipes. We have replaced pipes recently and the amount of crud that can build up is unbelievable (sorry I did not take photos).