Low water pressure may not be the reason for weak water flow from faucets. Check for a clogged aerator. You can fix it in 5 minutes.
Wrap the jaws of a pair of pliers with tape to keep them from scratching the aerator. Unscrew the aerator body from the faucet and remove all the internal components. Clean and reassemble.
If you get weak water flow when you turn on the faucet, don't assume your water pressure has suddenly gone bad. You could simply have a filter screen, or aerator, that's clogged. Remove the aerator as shown in the photo, rinse it out and reinstall it. If it's corroded or worn, take it to a home center and pick up a new one. Most stores have a slick gauge you can screw your old aerator onto to determine which replacement to buy. If you can't find a replacement for your aerator, soak the parts in vinegar overnight, scrub them with an old toothbrush and reinsert into the faucet (make sure to reassemble the parts in the same order you removed them).
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.