Why Does Hot Water Come Out Of My Cold Faucet?

If you've ever turned on your cold water faucet to brush your teeth or wash your face but hot water came out instead, you may have been confused as to why this occurred. There are a couple of reasons this could happen. You just need to figure out if it's a pipe, heating system or thermostat issue. As soon as you figure out the problem, a plumber can rectify your hot and cold water issues.

According to Reichelt Plumbing, one reason hot water could be coming out of your cold water faucet is the proximity of the pipes. In some cases, plumbing needs to fit in tight spaces, so your hot and cold water lines could be too close. Hot and cold water lines are supposed to run parallel to one another, but they can also end up close to each other as they're running up to the faucet. This could cause the heat of the hot water pipe to interfere with the cold water line.

Another reason hot water could be coming from your cold water faucet is due to the heat transfer from ventilation ducts. According to Reichelt Plumbing, if a forced-air heating system is running, the metal surface on the ventilation ducts could get warm. If your cold water pipe is close enough to the ductwork, heat could be transferred and warm up the water in your cold water line.

If your pipes are far apart and there isn't any heat transfer, check your thermostat. If your thermostat isn't working correctly, that could be the cause of your problem. For those who have water expansion tanks, the thermostat is located inside the immersion heater. If the thermometer malfunctions or breaks inside the immersion heater, your water could overheat and flow into the cold water pipes.

The last issue you may be having depends on whether you have copper pipes or not. According to Reichelt Plumbing, copper is very heat conductive, which means it's super easy for heat to pass through it. If you have copper pipes, when you run hot water in the faucet, the plumbing could heat the entire faucet over time.

If hot water is coming out of your cold water faucet, assess how long this has been happening. According to Reichelt Plumbing, it's common for warm water to come out of a cold water faucet temporarily. If this keeps happening, though, or the cold water never comes back, you need to hire a professional to look at your pipes.

Although it may seem like a simple issue, Len the Plumber points out that you can't measure how hot the water will become, and you can burn yourself the next time you turn on your cold water faucet. Depending on your issue, Reichelt Plumbing says the solution can be as easy as insulating your pipes to restrict heat transfer. Or you may need to rework your whole plumbing system.