A clogged toilet is incredibly stressful. In addition to depriving your bladder of the release it needs, it can overflow, flooding your floors with dirty water, rendering the entire bathroom unusable. Aside from being an old toilet model, toilets can get clogged for many reasons.

Insufficient water flow

Your toilet cistern may not have enough water, so check your water supply and make sure it's fully turned on. Some cisterns have an indicated fill line, so make sure the water level is set to that level. For this, you need to adjust the float valve (and also the ball valve).

Waste accumulation

Cigarette butts, tampons, napkins, Band-Aids, paper towels, etc., while they may seem too small or thin to form a barrier, they certainly contribute to a lot of waste buildup. Once trapped between the drainage curves, you can't handle the trusty plunger alone.

Root

Drainage is nutrient-rich, at least for plants. When tree roots find this water sanctuary, they will try to get into your drain, and even the tiniest leak can completely clog the drain. Not only will this affect your toilet, but your other drains as well.

Scale

These are white or rust-like hard water deposits that can clog the toilet's porthole (located below the toilet rim). When limescale is present, it reduces the toilet's flushing ability until it can no longer use enough water to flush waste.