It could be due to the main sewer drain being clogged by tree roots. Most older homes will have these issues and will need to get their pipes cleared every two years.
Do you have an older house and notice the water pressure isn't what it used to be? You may need to update your plumbing. Over time the old galvanized pipes can become corroded and build up so much that they can become completely clogged.
Soldering is a very reliable and great way to plumb, but it is not the only way.
Did you know your home plumbing system makes up about 15 percent of your total home value? That's an important investment. It might be smart to learn when to call the plumber.