How to Backflush a Hot Water Supply Line

Get your hot water flowing again.

Before you call a plumber to repair a hot water faucet with low flow, try backflushing it yourself. You can perform the process with a single tool. Essentially, you need to build up pressure in the pipes to blast the flow-blocking sediment backward into the bathtub. All it takes to do this is a way to prevent the water from flowing from your sluggish faucet.

Things You'll Need

• Paper towels
• Wrench

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Instructions

1. Shut off the hot water heater and its service valve. You can usually find this valve attached to a pipe that's coming out of the top of the heater in the basement.

2. Remove the aerator at the end of the spout with the lowest water pressure. To remove it, simply twist it to the left until it unscrews. If necessary, you can use a wrench to remove it.

3. Tear off a small piece of paper towel, roll it unto a ball about the size of the faucet opening and press it inside the aerator. Screw the aerator back on the spout.

4. Plug the bathtub or laundry room sink drain and turn on the hot water.

5. Turn on the cold water at the sink with the plugged faucet. The paper towel will prevent the water from flowing and will force it back through the pipes.

6. Check the bathtub or laundry room sink for debris. If there's sediment in the tub, you have successfully backflushed the pipe. Leave the hot water faucet on.

7. Shut off the cold water valve on the plugged faucet. Unscrew the aerator and remove the wad of paper towel, then replace the aerator.

8. Turn the water heater and service valve back on again. Hot water will start to flow into the tub. Allow it to run until the water comes out completely clear. Catch as much of the sediment as possible with a paper towel before draining the tub.

9. Turn on the hot water on the backflushed faucet to test the flow.

Tips & Warnings

• You can also use a rubber gasket or a coin inside the aerator to block the flow of water.

References

• Plumbing Geek: Back Flush Clogged Pipes
• Mosby Building Arts: Plumbing Water Heater Backflushing Hot Water Pipes