Good point about the anti-scald valve—I've seen those cause issues too, especially in newer fixtures. But before diving into fixture-specific troubleshooting, have you checked if the plumbing lines themselves are properly sized? Sometimes older homes or DIY remodels end up with undersized supply lines, and that can amplify pressure drops when toilets flush or appliances kick on. Had a similar issue at a property last year; turned out the previous owner had replaced some copper lines with smaller-diameter PEX tubing, causing noticeable temp swings whenever someone flushed. Upgrading to properly sized lines made a huge difference. Might be worth taking a quick look at your plumbing layout—any chance you've got mixed pipe sizes or recent plumbing modifications?
- Good suggestion on checking pipe sizes, but honestly, before tearing into walls or swapping out plumbing, I'd double-check simpler stuff first.
- Had a similar issue myself—turned out the shower valve cartridge was worn out and couldn't handle quick pressure changes anymore.
- Not saying undersized pipes aren't possible, just that it might be worth inspecting valves/cartridges first... cheaper and easier fix if that's the culprit.
Definitely agree with checking the cartridge first—had the same issue myself. Also, installing a low-flow toilet fill valve can help reduce sudden pressure drops... saves water too, so it's a win-win. Worth trying before anything drastic.
Had the same cold-shock experience myself a while back—almost slipped and fell scrambling away from the icy blast, haha. Agree with checking the cartridge, but I'd also suggest double-checking your water heater's temp settings. Sometimes they're set lower for safety (which I totally get), but bumping it up just a tad made a noticeable difference at our place. Obviously, don't crank it too high... nobody likes surprise scaldings either.
Had this same issue pop up on a job a couple months ago—it's pretty common, actually. The cartridge is definitely worth checking, but I'd also suggest looking into your plumbing layout. Older homes often have shared water lines between the toilet and shower, causing pressure drops when flushing. Installing a pressure-balancing valve or upgrading to separate lines usually helps. Adjusting your heater temp can mask the problem temporarily, but addressing the plumbing itself is usually the better long-term fix. Good luck... cold shocks aren't fun at all.
