The complete guide
How to Choose a Bath Plug That Actually Holds Water
The problem with the plug you already have
Almost everyone has had the same bath. You run it hot, get in, and ten minutes later the water level has quietly dropped two inches. You top it up. It drops again. By the end you have used twice the hot water and the bath was never really warm.
The cause is nearly always the plug. Rubber plugs harden and shrink with age, and once the rubber loses its spring it cannot press tightly against the drain wall. Pop up wastes develop the same problem from a different direction, when the seal ring wears or the linkage drops a few millimetres out of alignment. Either way you get a slow leak that is too small to see and too big to ignore.
The usual advice is to replace the plug. That sounds simple until you try it. Drain openings are not standardised, old baths use sizes that nobody stocks, and swapping a pop up waste means getting under the bath with a wrench. A lot of people give up and live with the leak.
A flat silicone drain stopper sidesteps all of that. It does not go into the drain at all.
How a flat stopper works
Think of it as a lid rather than a cork. The silicone disc is much wider than the drain opening, so it rests on the flat area of the tub floor around the waste. When you start filling, the column of water above presses down on the disc. The more water, the firmer the seal. It is self tightening in a way a wedged plug is not.
Underneath sits a suction cup. Its main job is to keep the stopper centred while you run the water, because a loose disc can drift off the drain before the water has enough weight to hold it. Press it down with your thumb and it stays where you put it.
That cup earns its place a second time after the bath. Stick the stopper to the tiles or the inside of the tub and it dries in the air instead of sitting wet in a cupboard. Small thing, but it is the difference between a stopper that stays fresh and one that develops a smell.
Removing it is a single movement. Lift one edge, air gets underneath, the seal breaks, the water goes.
Does your bath suit this design?
This is the question that decides everything, and it is worth two minutes before you buy.
Run your hand over the floor of the bath around the drain. You are feeling for a flat, smooth ring of surface at least a few centimetres wide in every direction from the opening. Enamel baths, acrylic baths, stainless steel sinks and most laundry tubs usually have exactly that.
What does not work well is textured non slip bath flooring, because the raised pattern leaves channels for water to travel along. Heavily pitted old enamel has the same problem. A strongly curved basin, where the bowl slopes sharply right up to the drain, gives the silicone too little flat contact.
If your pop up waste sits proud of the tub floor, the disc will bridge over it and leave gaps. Some pop up mechanisms lift straight out, which solves the issue. Others are fixed. Check before you order.
This honesty matters more than a sale. When the surface is right, a flat stopper holds beautifully. When it is wrong, no amount of pressing will fix it.
Who it suits
People with an old bath and a missing plug. This is the biggest group. Where the original plug is long gone and nothing in the hardware shop matches the opening, a cover that works over the top solves the problem without any measuring.
Anyone who takes long baths. If the reason you are reading this is that your water goes cold too fast, the fix is a plug that does not leak. A seal that gets tighter as the bath fills is well suited to a long soak.
Households with kids. No chain to catch, no hard rim, no small parts. A child can lift it when the bath is done. It is a simple item and that is the appeal.
Renters. You are not modifying anything. Nothing is screwed in, glued on or plumbed. When you move, it comes with you.
Kitchen and laundry use. The flat floor of a stainless steel sink is close to ideal for this kind of seal, so one cover often ends up doing duty in more than one room.
Comparing your options
Against a standard rubber plug, the flat stopper wins on fit and loses on universality. A rubber plug only works if the size matches. This covers almost anything, but only on smooth surfaces.
Against a pop up waste repair, there is no contest on cost or effort. Replacing a waste means tools, access and often a plumber. A silicone cover takes zero installation.
Against a cloth or improvised plug, which plenty of people resort to, this is cleaner, seals better and does not leave fibres in the drain.
Against nothing at all, the saving is in hot water. A bath that holds temperature for thirty minutes instead of ten is a real reduction in the tap you run.
Sizing and the numbers
The cover is 15 cm wide and 18.5 cm high. That is the stopper itself. You do not need to measure your drain hole, you need to check that the flat area around it is wide enough for the disc to land on. Lay a saucer of roughly that size on your bath floor and see how it sits. If it rests evenly, you are fine.
Weight is 68 grams, which is light enough to pack in a toiletry bag. People who travel to places with unreliable hotel plumbing often carry one for exactly that reason.
It is sold as a single unit. One item, one pack.
Keeping it working
The seal depends on two clean surfaces meeting. That is the whole maintenance story.
Rinse the underside after a bath, especially if anyone has washed hair. A single strand of hair across the sealing edge is enough to start a slow drip. Wipe the tub floor around the drain at the same time.
Once a week, give it a wash with warm water and a drop of dish soap to cut through soap film, then rinse properly so no residue stays on the sealing face. Avoid abrasive scourers, since scratches in the silicone become leak paths.
Store it flat or stuck to a wall. Long periods folded tightly can crease the material. Keep it out of direct sun when it is not in use.
If it starts leaking, do not assume it has failed. Nine times in ten the fix is lifting it, rinsing both faces and pressing it back down.
The short version
A flat silicone bathtub drain stopper is the easiest answer to a bath that will not hold water, provided the floor around your drain is flat and smooth. It covers the drain instead of plugging it, so it works where conventional plugs no longer fit. The suction cup holds it in place and doubles as a way to hang it dry.
It is 15 cm by 18.5 cm, grey silicone, 68 grams, and it needs nothing installed.
Check your bath floor first. If it is flat where the stopper will sit, this will hold your water and your heat. If it is textured or steeply curved, be honest with yourself and look at a push in plug instead. Buying the right thing beats buying the clever thing.