Shower doors ensure that the shower remains watertight by using various types of seals and sweeps. These seals and sweeps are made of materials such as vinyl, polycarbonate, and rubber. Here are some of the ways that shower doors can be made watertight:

Bottom sweeps: The most common type of shower door seal is the bottom sweep, which extends through the entire bottom width of the door and is installed at the door bottom. The bottom sweep has a drip edge on one side which is fixed towards the inner side of the shower area. Shower door bottom sweeps can be installed on framed as well as frameless shower doors with your bare hands.

Proper Seal Design: Most shower doors are designed with a sealing mechanism, which can include gaskets, sweeps, and seals made of materials like rubber or vinyl. These seals are strategically placed along the door's edges, bottom, and sides to create a tight seal when the door is closed.

Magnetic or Mechanical Closures: Many shower doors feature magnetic or mechanical closures. These mechanisms ensure that the door stays securely closed during use, which helps prevent water from escaping.

Overlap and Overhang: Shower door designs often incorporate an overlap and overhang arrangement, which ensures that the door covers the shower threshold or curb. This design minimizes the gaps through which water can escape.

Angled Design: Some shower doors are angled slightly inward towards the shower area. This design encourages water to flow back into the shower rather than outward.

Thresholds and Curbs: Shower enclosures may include thresholds and curbs, which are designed to contain water within the shower area. The shower door typically aligns with these thresholds to create a continuous barrier.

Professional Installation: Proper installation by a qualified professional ensures that the shower door is aligned and sealed correctly. This includes ensuring that the door is level and that the seals and sweeps are properly positioned.

High-Quality Materials: The use of high-quality materials, including tempered glass and durable framing, ensures that the door remains stable and secure, contributing to its water-tightness.

Regular Maintenance: Periodic maintenance, such as cleaning the seals and sweeps, can help maintain their effectiveness in preventing leaks.

It's important to note that while shower doors play a significant role in maintaining a watertight shower, their effectiveness also depends on other factors, including the condition of the shower enclosure, the proper slope of the shower floor, and the quality of the plumbing fixtures. A well-designed and properly installed shower system, including the door, is crucial for ensuring a watertight shower experience.

If you experience water leaks or notice that your shower door is not maintaining a watertight seal, it may be necessary to inspect the seals, sweeps, and door alignment, and, if needed, perform maintenance or adjustments to ensure the door functions as intended.