You're taking a nice warm shower, gently rinsing away a day's worth of grime and stress. Then, all of a sudden, the hot water temperature spikes. You leap backwards to escape the flow of scalding water then simply stand there in the cold, gently rubbing your skin. Looks like someone flushed a toilet in your house.
If this scenario sounds familiar, you probably have a trunk and branch plumbing system, with individual pipes branching out from a common line. Whenever cold water is diverted to your toilet during a flush, there's less cold water available to balance your shower's water temperature. If you can't take the heat, it's time to consider your options. A local plumber will certainly come in handy.
Reduce Water Flow to Your Toilet
Reduce how fast water rushes to your toilet. Though doing this could mean slower, noisier fill times for your toilet, it can also help balance your bathroom's cold water distribution during toilet flushes. Partially close the toilet supply valve. The relevant knob can be found on an exposed pipe behind your toilet. With less cold water being redirected to your toilet during a flush, you'll have more left to balance your shower's hot water supply. Again, make sure you consider the resultant longer toilet-refill time; if you're the type of person who likes to flush the toilet more than once per session, you'll have a lot more waiting to do.
Reduce How Much Water Your Toilet Needs
Reduce the amount of water your toilet needs. Toilets are designed to collect a certain amount of water in their tank before the refill pump ceases activity. If you're willing to work with less overall water and water pressure during toilet flushes, you can add weights inside your toilet's tank to keep the water level higher. Thinking its job is complete, the refill pump will cut off sooner. Diverting less cold water to your toilet during flushes can help negate a jarring rise in your shower's water temperature. Many people use a brick or rock for this purpose. Make sure you use an object that will not rust or dissolve when submerged fora prolonged period of time.
Update Your Plumbing
If smaller fixes don't get the job done to your satisfaction, hire a contractor to give your plumbing an overhaul. Plumbers can run separate pipes to each of your home's water fixtures, starting from a central balancing manifold.