Bathroom door locks have to provide privacy and security, and they should be long-lasting, but unlike entry door locks, they should be relatively easy to break should an accident happen inside the bathroom. You might find keyed locks on public bathrooms, but you'll seldom find one on a residential bathroom door because, after all, who wants to go looking for a key when you're safely at home with your family? In lieu of a key, many residential locks have a spring-loaded lock release that you can activate from outside the bathroom with a small metal rod.
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People for whom security and privacy are paramount may provide a latch or deadbolt that can only be disengaged from inside the bathroom. If your bathroom doesn't have a locking door knob, this may be the easiest and most economical way to lock the bathroom door, but beware. Bathroom doors are often made of flimsy material, and the screws holding a door latch can break loose.
Ball-Type Privacy Locks
A ball-type doorknob is roughly spherical and fits into the palm of the hand, and this is the type you'll find on most bathroom doors. Some have a silver patina, others have a bronze one and some are coated with a matte-black finish, and if they feature a lockset, the inside handle has a button that you push or a turn to lock the door. The outside handle has a small hole about 1/8 inch in diameter for the emergency release rod that disengages the lock.
Easy-to-Operate Lever Handles
Lever-style locksets work the same way as ball-type ones, and it's easy to find one that features the hole for the emergency rod. Lever-style handles are easier to operate than ball-type ones. Instead of grasping the ball and turning, which is often more difficult when your hands are wet or greasy, you can open the door by pushing down with your elbow if your hands are full. This is the type of bathroom lockset required by the Americans with Disabilities Act, so it's the type you should use if you want to make a bathroom accessible.
Bathroom Latches and Deadbolts
Older houses often feature nonlocking antique doorknobs with ornate finishes installed in tandem with a deadbolt operated with a skeleton key that has long since been lost. Replacing these knobs can be problematic because the holes that have been drilled for them are often too large for a standard doorknob. The most practical way to lock the door is to install a latch or deadbolt, even though that makes emergency access to the bathroom difficult or impossible unless you break down the door.
A barrel-bolt lock is a common and inexpensive solution for such situations, and it's easy to install, but a chain lock is preferable. If an accident happens, it's possible to partially open the door and jimmy the chain or saw through it to open the door. The simplest lock of all, though, is the standard hook and eye latch, and if you install this the right way, an emergency responder should be able to partially open the door and disengage the hook with a knife or similar implement.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker and Family Handyman.