Q: When I turn on the hot water in my bathroom sink, the water comes out in spurts. I also feel knocking and shaking in the hot-water pipes in the basement. Whats wrong?
A: If this is happening in only one faucet, it is possible you just have a clogged aerator in the faucet. If you are getting the same symptoms in other fixtures, including sinks and shower heads, and you have an older water heater (made in 1993-97) you are probably having a dip-tube problem.
Start by removing the aerator from the tip of the faucet. It screws out, but if it hasnt been removed for a long time you might need to use pliers to get it started. If the aerator is simply clogged with minerals, it can be cleaned by soaking it overnight in white vinegar, but it is best to buy a new one for a few dollars at a home center. But if you find small pieces of plastic in the aerator, suspect the dip tube.
Defective dip tubes plastic tubes intended to guide incoming cold water to the bottom of heater tanks were installed in many brands of water heaters during the years mentioned above. The tubes often broke up into small pieces that were moved into pipes and fixtures, causing clogging.
If there is a dip-tube problem and your water heater is more than 10 years old, the best bet is to replace it. All aerators and shower heads should be removed and the pipes thoroughly flushed out.