Usually, poor water pressure is caused by clogged pipes. But if you've already replaced them or have a newer house with new pipes, try the obvious first. Make sure the shutoff valves near the water meter are fully open. Sounds basic, but plumbers still have to charge for a service call to simply turn a valve handle! Then check the water pressure. If your house is on city water, ask your local water department for a pressure reading. A reading of 45 to 55 psi is ideal.
Or test the water pressure yourself with a pressure gauge (sold at home centers). Hook up the gauge to an outside water spigot, turn on the water, and you'll get an instant reading. If the reading is low, the city may be delivering water at a low pressure (less than 40 psi). If the city isn't likely to boost the pressure, consider installing a water pressure booster system, starting at $300 at a home center or plumbing store, or online. Any setting over 80 psi will wear out the washers on your plumbing fixtures. The system we show is only made to fit 1-in. pipe. If you install it yourself, apply for a plumbing permit so your work will be inspected. Some municipalities require a reduced pressure and backflow preventer to be installed when a water pressure booster is hooked up.
If the pressure reading is adequate, you may have obstructions or some pipes that are too small. Call in a licensed plumber to evaluate your system.