It's easy to start running a bath and then be distracted and forget that gallons of water are filling up that bathtub. The overflow outlet is an important part of your bath plumbing and ensures that when you get chatting on the phone and forget the bath, you won't suddenly be surprised by gallons of water pouring down the stairs. However, it's important to keep the outflow clear as well as the drainage pipes; otherwise, you might still end up with a wet floor.
Overflow outlet drainage
The plughole and the overflow outlet share the same drain. The two holes are connected by the drain waste, a vertical length of piping that links the overflow and the plughole on the outside of the bath and drains water away into the main drainage system. The website MakeMyOwnHouse.com advises that you make sure the seal is watertight when you attach the drain waste to the plug and overflow outlets, and that you don't tighten the washers so tight against the bath exterior that they snap.
Keep the drain waste clear
Keeping the drain waste clear of blockages is important if you're going to maintain good drainage as well as making sure your overflow drains when it needs to. You can insert a trap into the plughole that catches stray hairs which can accumulate, attract bath scum and make a blockage worse. Boiling water is a useful de-gunker which you can pour down the drain once a week to keep the pipes clear.
Overflow outlet pipework
Overflow outlet facings that are fixed inside the bath are usually made of stainless steel, and modern drainage pipes are made from hard, durable plastics. The Victoria Plumb website states that the most commonly used is polypropylene, which is hard and strong enough to cope with hot and cold drainage as well as household cleaners such as bleach and liquid cleansers.
Unblocking the drain
If you're having problems with the drainage and the water isn't draining away, unblock the pipes with a sink plunger before you need to use chemical unblockers. The outflow is directly connected to the plug drainage by the drain waste, so cover the outflow with a wet cloth to block any air from entering, place the bulb of the sink plunger over the plug hole, and position it so as to create a vacuum. Pull the plunger up quickly. The blockage should clear and the water will drain away.