Finding there's no cold water in your house is frustrating, but having a problem only with temperature helps narrow down where the problem might be occurring. That's because water enters a home or building through one pipe from the water main. This pipe splits off at the water heater, with one pipe going to the hot water heater and another continuing into the home to deliver cold water where it's needed.
If only cold water is affected, that eliminates all the hot water piping as a source of the trouble. Instead, you can focus on the network of cold water pipes that run through the walls of the house. The possible causes of a cold water tap not working, however, can still be just as serious as those that affect any pipe, regardless of water temperature.
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Safety Considerations to Take if Your Cold Water Isn't Working
If you find that there's no cold water in your shower or a cold water tap isn't working, don’t start tearing down your walls to get to possibly blocked pipes. If you do that, you could misjudge where the blockage is and bust open the wall unnecessarily. When dealing with an unknown blockage in your water pipes, call a plumber to deal with finding and repairing the problem.
If there's no cold water in the house at all, proceed with caution when turning on any taps since the water that comes out will likely be hot. Consider buying bottled water for washing your hands until the problem is fixed, or set the temperature on the heater as low as possible.
1. Shut-Off Valve
If you live by yourself and haven't had anyone over, a shut-off valve probably wont be the reason the cold water stopped flowing, but if you have children, mischievous roommates or forgetful repair people, the lack of cold water could be due to something as simple as the shut-off valve. If there's no cold water in the house at all, then the shut-off valve under each sink becomes less of a possible culprit.
This valve is located under the sink; you'll see two knobs near the pipes leading to the hot and cold water lines. Try turning the cold water knob and seeing if the water starts up again. The cold water knob should be on the right, if you have a one-handled faucet.
2. Frozen or Blocked Pipes
Hot and cold water travel to your sink in different pipes, and in winter, it's possible that part of the cold-water pipe leading to your sink has frozen. After you've figured out which sinks have no cold water, you might be able to figure out where the frozen section of pipe is — or at least the general area -— if you have plans showing the pipe layout for your home or apartment.
A more frustrating and difficult-to-fix cause could be a blockage in the pipe, such as from debris that made it inside from the water main, or corroded metal that's flaked off the inside of the pipe. If only cold water is affected, that would indicate the blockage is not outside, as the hot water remains unaffected.
3. Pressure Balancing Valve
If there's no cold water in your shower but cold water comes out of every other faucet just fine, then the problem lies in the shower faucet cartridge. This cartridge contains a pressure balancing valve that sometimes fails, thus preventing cold water from flowing out of the shower head.
Removing and replacing the cartridge should fix the problem. Sometimes a special tool called a cartridge puller is required, in which case it might be more convenient to call a plumber.