Swimming pool maintenance requires a filter system working together with chemicals to achieve water clarity and a safe pool environment for swimmers. Here are the basics to keeping your swimming pool clean and bacteria free. 1.  Sanitize your pool with a stabilized chlorine product to provide protection against bacteria. These generally come in stick or tablet form and are fed into a distribution container near the pump and filter system.    2.  Use an algae preventive or inhibitor to help keep the more than 15,000 kinds of algae from ever getting started. This liquid product is simply poured into the water near the skimmer intake so that the pump system can distribute it to all areas of the pool.    3.  Shock your pool on a regular basis or about every two weeks. This will get rid of water-soluble bather waste. 4.  Find a pool professional or supply dealership that has a water test facility (or access to one) and that offers computer analysis of samples you bring in. Many of the larger companies offer this service free of charge so you will buy pool chemicals from them.       Tips:  Look for pool companies that offer weekly maintenance services if you're not committed to taking care of the pool yourself. The weekly service and the great pool conditions can often be less expensive than the extra chemicals and the work involved in dealing with a poorly maintained pool.      Troubleshooting Your Pool:     1.  Listen for excessive pump noise as a warning of possible problems in that area. Today's newer pumps are sealed units that don't require any maintenance, but rubber or composition pump seals can go bad and result in bearing failure or electrical shorts.    2.  Replace any pump that's more than 7 or 8 years old and is in need of repair. The newer models are more efficient at moving larger volumes of water with less energy, saving you money on many fronts: You'll need a smaller, less expensive pump; you'll have lower monthly utility bills; and better circulation means better filtration and fewer chemical requirements.    3.  Keep a close eye on the pressure gauge. An inoperative pressure gauge means you can't tell when water pressure begins to build from the normal levels indicated by a clean, efficient filter and the higher pressure of a filter in need of cleaning. High pressure means unnecessary strain on the pool pump and a less efficient filtering system.    4.  Know what kind of filter you have and keep it clean.