what causes decreased water flow to a house
Check them to make sure they're fully open. Water softeners can also cause low water pressure. If yours doesn't have an obvious bypass valve or bypass feature, have a plumber divert water around it to see if house pressure improves. If it does, the softener probably needs repair or replacement.
Water Leaks. Any damage to the pipe that results in a leak, whether large or small, will result in a lower water pressure. The issue here is how to determine if you have a leak or not. The trick is to read the meter and not the bill. To do this, you should shut off all water taps inside and outside the home.