If you share a home with people and have your own bathroom, it can be very frustrating when your sink and tub keep suddenly backing up when you're not using them. Clogs like these (where water comes back up through the drain when you're not using the fixture) are usually due to a clog in one of the common drains that are shared between your bathroom's fixtures and a nearby bathroom. Snaking the drain is the easiest solution. But if it keeps happening, and no one else reports that their sink or tub is backing up, you have to wonder what's going on. It could be due to how your home's plumbing is configured, due to people not paying attention, or a combination.
Your Drains May Form the Easiest Path
When water can't drain through its normal plumbing route due to a clog, it's going to flow somewhere. And, in a drain system where water is being poured down one drain, the easiest way to flow is to the next unclogged pipe. That's often the one leading to your sink or tub. So it's not that there is something very wrong; it's that your bathroom just happens to be the most convenient place where the water can go.
Keeping the common drains clear is essential, which means everyone has to be aware of what they're putting down the drains in their bathrooms. The next time you have to have the plumber come over to unclog a pipe, you may want to have them snake other drains in the house as well. Speak to your housemates about what they're putting into the drain to try and identify why you keep having these backups.
They May Think Backups Are Normal
It's entirely possible that your housemates might not realize that the slow drains they've been dealing with are not normal. If you're brought up in a home with slow drains, for example, that's your default image of how drains often work, even if you have seen drains that aren't slow. That's when you have a plumber clear out all the drains, both in the fixture and in the common drains, in the entire house.
With the Water Running, They Might Actually Not Notice
If someone's got their bathroom sink faucet running at a fast rate, the water that hits the drain can still swirl and pool around the drain as it tries to get through. If the common drain between that sink and your sink is clogged, the water will back up, but the person using the first sink may see only the stream from the faucet hitting the drain with speed and causing some splashing. So they may not even realize that part of the water they see in the sink at that point is due to slow draining.
Call a plumber and have them clear all the drains in the house. Then ask your housemates what on earth they've been putting down the drains to make the common drains keep clogging up.
Contact a plumber for more information.