Home repair involves the diagnosis and resolution of problems in a home, and is related to home Maintenance to avoid such problems. Many types of repairs are "Do it yourself" (DIY) projects, while others may be so complicated, time-consuming or risky as to suggest the assistance of a qualified handyman, property manager, contractor/builder, or other professionals. Repair is not necessarily the same as Home Improvement, although many improvements can result from repairs or maintenance. Often the costs of larger repairs will justify the alternative of investment in full-scale improvements. It may make just as much sense to upgrade a home system (with an improved one) as to repair it or incur ever-more-frequent and expensive maintenance for an inefficient, obsolete or dying system. For a DIY project, it is also useful to establish limits on how much time and money you're willing to invest before deciding a repair (or list of repairs) is overwhelming and discouraging, and less likely to ever be completed. Repairs often mean simple replacement of worn or used components intended to be periodically renewed by a homeowner, such as burnt out light bulbs, worn out batteries, or overfilled vacuum cleaner bags. Another class of home repairs relates to restoring something to a useful condition, such as sharpening tools or utensils, replacing leaky faucet washers, cleaning out plumbing traps, rain gutters. Because of the required precision, specialized tools, or hazards, some of these are best left to experts such as a plumber. One emergency repair that may be necessary in this area is overflowing toilets. Most of them have a shutoff valve on a pipe beneath or behind them so that the water supply can be removed while repairs are made, either by removing a clog or repairing a broken mechanism. Perhaps the most perplexing repairs facing a homeowner are broken or damaged things. In today's era of built-in obsolescence for many products, it is often more convenient to replace something rather than attempt to repair it. A repairman is faced with the tasks of adequately identifying the problem, and then finding the materials, supplies, tools and skills necessary to sufficiently effect the repair. Some things, such as broken windows, appliances or furniture can be carried to a repair shop. However, there are many such repairs that can be learned easily enough such as dealing with holes in plaster and drywall, cleaning stains, repairing cracked windows and their screens, or replacing a broken electrical switch or outlet. Other repairs may have some urgency, such as a broken water pipes, broken doors, latches or windows, or a leaky roof or water tank, and this factor can certainly justify calling for professional help. A home handyman may become adept at dealing with such immediate repairs, to avoid further damage or loss, until a professional can be summoned. Periodic maintenance also falls under the general class of home repairs. These are inspections, adjustments, cleanings, or replacements that should be done regularly to ensure proper functioning of all the systems in a house, and to avoid costly emergencies. Examples include annual testing and adjustment of alarm systems, central heating or cooling systems (electrodes, thermocouples, and fuel filters), replacement of water treatment components or air-handling filters, purging of heating radiators and water tanks, defrosting a freezer, vacuuming refrigerator coils, refilling dry floor-drain traps with water, cleaning out gutters, downspouts and drains, touching up worn house paint and weather seals, and cleaning accumulated creosote out of chimney flues, which may be best left to a chimney sweep.