Why Has My DSL Slowed Down?

By William Jensen

Always use DSL filters with telephones.
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Digital Subscriber Line (DSL) is a type of Internet access that normally offers high connection speeds. However, various problems can cause DSL to slow down, especially when you make changes to your computer or telephone equipment. After determining why your DSL has slowed down, you may be able to correct the problem. Ask your Internet Service Provider (ISP) for help, or at least understand why you will have to accept a lower speed.


The distance from your home or place of work to the nearest telephone company office greatly affects DSL speed. Longer lengths produce slower speeds, according to DSLReports.com. Ranges from one to seven or eight miles yield gradually slower speeds; DSL service becomes unavailable at longer distances from the office. CCI Net indicates that the condition of telephone wires can affect DSL connection speeds as well. Moving to a street with older telephone lines or a longer distance to the telephone office may have caused your DSL service to slow down.

ISP Issues

Your ISP might be experiencing technical problems or could have changed the amount of bandwidth (data transfer capability) available. If you aren't at work, consider shutting down the computer for a few hours and waiting to see if the DSL connection speed improves. If the problem persists, contact the ISP for information by email or telephone and check their website for updates.

Computer Problems

Technical problems such as virus infection and poor software configuration can cause DSL to appear as if it has slowed down. Running a virus scan and examining Internet-related settings may help remedy such problems. Check the taskbar to determine if the computer is downloading a software update; this demands more from the Internet connection and slows it down.

Another possibility is that unfiltered telephone devices interfere with your computer's connection to the DSL service. Verizon warns that missing filters can cause DSL connections to slow down (See Reference 3). DSL users should connect filters to every telephone and answering machine on the same line as the Internet connection. Perhaps you installed a new telephone without the necessary filter just before your DSL slowed down.


Although DSL connection speeds prove more predictable than cable Internet and some dial-up systems, it's normal to experience some fluctuation with any type of Internet access. While many users will not notice a 10 or 20 percent drop in speed, someone watching high-resolution videos or downloading large files may see a difference. Try to determine a time of day when speeds become highest or find out if your Internet provider offers a higher speed option.