“Why Does My Water Switch Between Hot and Cold?”


Is your water screaming hot one minute, then freezing cold the next? It’s a common plumbing problem. The good news is, you don’t need to rip out all your pipes and start over. There are a lot of explanations for this phenomenon, including:


You Have a Tankless Hot Water Heater

Most tankless hot water heaters require a minimum flow of water to turn “on.” If you’re using a hot/cold faucet (like in the shower or in the kitchen), unless you have the water running very fast and very hot, your tankless heater may not be getting the signal that it’s time to heat up. An easy fix is to lower the setting on your hot water heater; try 110 degrees instead of 120. This can lower the threshold for signaling.


Your Anti-Scald Valve is Corroded

Most modern showers are plumbed with something referred to as an “anti-scald” valve. These valves basically integrate an internal thermostat into the shower’s plumbing to make sure no one inadvertently scalds themselves trying to turn the water on or off. Over time, it’s possible your anti-scald valve might corrode, affecting its ability function properly. This could be the culprit for your changing water temperatures, and it’s usually relatively simple for a professional plumber to switch yours out.


You Have a Problem With Your Mixing Valve

Also known as a TMV (thermostatic mixing valve), a mixing valve blends hot and cold water together to create the temperature you desire. They’re typically found in showers and kitchen faucets, and they do wear out. In fact, many mixing valves use wax thermostats, which themselves can be unreliable. Your best bet is to have a professional plumber check out your TMV to determine whether it’s time for a replacement.


Your Water Has to Travel a Long Way

The hot-cold-hot problem is usually worse on the second (or third) floor because of where the water heater is placed. It’s possible that the first burst of hot water is residual, followed by cold water that’s pushed through the pipes, then finished by water that finally heats up. The solution is simple: A recirculating hot water pump keeps water hot, so it’s always there when you need it. A plumber can install a hot water recirculator in conjunction with your current water heating system.
Is your plumbing acting up? It can be hard to articulate when something is “off,” but an experienced plumber can always help you get to the bottom of things. One thing you don’t have to live with is water that’s constantly switching between cold and hot.

One Call Plumbing is Charlotte’s trusted choice for both emergency and scheduled plumbing repairs. We have over 16 years of experience working with home and business owners to solve even the most complex plumbing issues.

Give our friendly team a call today to talk about your most pressing plumbing questions!