Last updated: 24 June 2026
Water outside the shower does not always mean you need a plumber.
If the leak is coming from the bottom of the shower door, the key is to check three things: the bottom seal, the threshold, and whether the water is actually starting somewhere else before running down.
If you are still not sure where the water begins, start with our guide to shower door leaking at the bottom before replacing any parts.
This page is more specific: how to seal a shower door at the bottom once you know the water is escaping under the glass, through the bottom seal, or across the tray entrance.
Quick answer: for water escaping directly under the glass, start with a bottom drip seal. If water is travelling across the tray, add a threshold seal or water bar.
Choose the Fix Based on Where the Water Is Escaping
Once you know the leak is around the bottom of the shower door, do not rush to buy a new seal straight away. First, look at what the water is actually doing.
| What you see | Better fix |
|---|---|
| Water is coming directly from under the glass | Replace the bottom drip seal with the right type |
| Water is still escaping from under the bottom seal | Check the bottom gap and fin length, and use a clear threshold strip if needed |
| Water is running across the tray entrance or tray edge | Add a clear threshold strip or water bar |
| The bottom gap is uneven from left to right | Measure the actual gap and choose a seal that covers it without dragging, using a threshold strip if needed |
| Water is coming from the bottom of the tray, frame, or fixed joint | Check the fixed joint and silicone instead of treating it as a normal moving-door bottom seal issue |
| Water starts from one bottom corner | Check the seal direction, end cut, and corner gap |
If the water path still does not match any of these examples, the Fixing Shower Leaks hub is the better place to compare leak patterns.
The Measurements Matter More Than the Old Seal
A bottom seal is usually simple to fit. The part that often goes wrong is choosing the size.
Start with the glass thickness. If the seal is too loose, it will not grip properly. If it is too tight, it may twist or deform as you fit it.
Then measure the door width. A seal cut too short can leave small gaps at the ends. A seal cut too long may catch on the side and make the door harder to open and close.
The last measurement is the gap between the bottom of the glass and the shower tray. This tells you whether the fin can make light contact with the tray or threshold strip. Measure the left side, the centre, and the right side. Many shower trays are not perfectly level, so one side may sit neatly while the other side drags or still leaves a small gap.
Write the measurements down, especially if the gap changes across the door. Before ordering, check them against our shower seal measuring guide rather than judging by the old seal alone.
If Water Comes from Under the Glass, Start with the Bottom Drip Seal
An old seal can look fine at first glance. It may still be clipped onto the glass and it may not look broken. The problem is often lower down, where the bottom shower door seal fin has become hard, curled, yellowed, or no longer sits close to the tray.
Even a slight lift along the bottom edge can give water a way out.
The old seal can be a useful clue, but it is not enough on its own. The replacement still has to match the glass thickness, the gap below the door, and the way the fin needs to sit.
The bottom fin should face into the shower area, so water is sent back onto the tray. If the fin faces the wrong way, the seal may look fitted, but the water will still be encouraged in the wrong direction.
A longer fin is not always better. If it is too long, it can press against the tray or threshold, drag as the door opens, bend out of shape, or pull the seal loose. The right fit is light contact, not heavy pressure.
This is where fin length is often misjudged. Our bottom seal fin length guide is useful when two sizes look close and you are not sure which one to choose.
Do Not Force the New Bottom Seal from the Middle
To remove the old seal, start at one end and pull it down slowly. In most cases, this will not damage the glass. Avoid using metal tools to prise it off, and do not twist the glass edge.
Once the old seal is off, clean the bottom edge of the glass. Remove limescale, soap residue, and mould before fitting the new strip.
A clip-on seal relies on the glass edge for grip. If there is still limescale on the glass, the new seal may look fitted but still fail to hold properly. That makes it more likely to loosen or slide off later.
Fit the new seal from one bottom corner and work it along the glass edge gradually. Do not press hard from the centre, and do not try to force the whole strip on by sliding it straight across from the start. That can make the seal sit unevenly.
Once fitted, open and close the door a few times. The bottom fin should not drag heavily, and the door should not become difficult to move. On a sliding door, also check that the fin does not catch on the track, rollers, or metal fittings.
If this is your first time replacing the strip, read the full bottom seal replacement guide before you start, especially if the seal needs cutting or the old strip feels tight.
If Water Runs Across the Tray Entrance, Use a Clear Threshold Strip
Sometimes the bottom seal is doing part of its job, but not enough to keep water inside the tray.
This is common with frameless shower doors, flatter tray entrances, or showers with no threshold strip already fitted. The bottom seal may guide most of the water back into the shower area, but once water reaches the tray entrance, it can still continue onto the bathroom floor if there is no second barrier.
In that situation, do not rush to replace the bottom seal with a longer fin. A better fix is often to let the bottom seal and a clear threshold strip work together.
The threshold strip should sit where the water naturally travels. With the door closed, look at where the bottom fin sits. The threshold should overlap sensibly with the seal so that water is stopped and sent back into the shower area, rather than passing between the two.
A threshold strip in the wrong position can create another problem. If it sits on the wrong side of the glass, water may collect between the strip and the bottom seal, then be carried out when the door opens. If it is too far from the glass, it leaves a channel for water to pass through. If it is too close, it may rub the seal and make the door harder to use.
Different tray edges leave different amounts of space for a threshold strip. Before choosing one, check our shower threshold strip choose guide to see which style is more suitable for the space at the bottom of your door.
The video below shows how a threshold strip helps return water to the tray during a normal shower-flow test.
When Sealing the Bottom Is Not Enough
Some leaks end up on the floor, but do not start at the bottom of the door.
If the first wet point is near the hinge, water may be starting at the side and running down the glass. Replacing only the bottom seal is unlikely to fix that.
If one bottom corner keeps getting wet, the problem may be around the corner joint, vertical seal, end cut of the bottom seal, or where the threshold meets the door.
If water is coming from between two glass panels, especially on a sliding or overlapping shower door, the overlap seal may need attention rather than the bottom seal.
If water appears from the bottom of a frame or track, treat it differently from a standard frameless door bottom leak. It may be related to a fixed joint, drainage in the frame, or old silicone.
After Fitting, Check Water Direction and Door Movement
Once the bottom seal or threshold strip is fitted, do not judge the result by appearance alone.
Close the door and run the shower normally for a few minutes. Watch whether water still appears from under the glass, across the tray entrance, or near a bottom corner.
Then open and close the door a few times. The bottom fin should not drag heavily, and it should not carry trapped water out as the door opens.
If the door suddenly becomes difficult to move, the fin may be too long, the threshold may be too close, or the two parts may overlap too much. A small trim to the fin or a check of the threshold position may be enough.
If you have replaced the bottom seal, added a threshold strip, and the leak has still not improved, avoid guessing. Take photos of the leak point, the bottom seal, the glass thickness, and the gap size, and send them to SIMBA for help. That is usually more useful than buying another similar part.
Mistakes That Make Bottom Leaks Worse
Many failed bottom-seal repairs are not caused by a lack of new parts. They happen because the fix is aimed at the wrong part of the leak.
Buying the same style as the old seal, choosing a longer fin to cover every gap, placing the threshold too far from the glass, or filling the bottom of a moving door with silicone may all look like quick fixes. But the original water path may still be open.
Water on the bathroom floor only shows where the water ended up. It does not prove the leak started at the bottom.
A longer fin is not always more watertight either. It may make the door harder to move, or wear, bend, and loosen more quickly.
Threshold position matters as well. If it is fitted on the wrong side, water can sit between the threshold and the seal, then be carried out when the door opens. If it is too far from the glass, water can still pass through the gap.
Silicone is not the best answer for the bottom of a moving door. It is better suited to fixed joints, not to an edge that needs to open and close.
Still Not Matching What You See?
Some bottom leaks turn out to need a more specific fix. These guides may help you narrow it down.
| Situation | Recommended guide |
|---|---|
| You want to understand why water is leaking from the bottom | Why Your Shower Door Is Leaking at the Bottom |
| You need to replace an old or damaged bottom seal | How to Replace a Shower Door Bottom Seal |
| You are not sure which bottom seal shape or size you need | Shower Door Bottom Seal Choose Guide |
| You have a large or uneven gap under the glass | Shower Door Uneven Gap Solution |
| You need to choose a threshold strip or water bar | How to Choose a Shower Threshold Seal |
Conclusion
A good shower bottom seal does not need to block every small gap. It needs to stop water leaving the tray during normal use.
If water comes directly from under the glass, start with the bottom drip seal. If water runs across the tray entrance, consider a clear threshold strip or water bar. If a new seal still allows a small amount of water to pass the entrance, using both together is usually more reliable than fitting an even longer fin.
A few minutes spent watching the water path will usually save you from buying the wrong part.
Frequently Asked Questions
Can I seal the bottom of a shower door myself?
Yes. In most cases, you can seal the bottom of a shower door yourself by checking where the water escapes, fitting a bottom drip seal, and adding a threshold seal if water runs across the tray.
What is the best way to seal the bottom of a shower door?
For a simple leak under the glass, a bottom drip seal is usually enough. If water is also running across the tray, add a threshold seal or water bar. For uneven trays or stubborn leaks, both together are often more reliable.
Which way should the drip fin face?
The drip fin should face inside the shower tray. This sends water back towards the drain instead of out onto the floor.
Do I need a threshold seal as well?
Not always. If the bottom seal already meets the tray properly and water stays inside, you may not need one. A threshold strip is useful when the tray is flat, the gap is uneven, or water still crosses the edge after fitting a bottom seal.
Can I use silicone along the bottom of the shower door?
It is usually not the best fix for a moving door. Silicone can restrict movement, look messy, and make future replacement harder. A clip-on bottom seal or threshold strip is normally cleaner and easier to maintain.
Why is it still leaking after I fitted a new seal?
Check the basics first: the fin direction, the gap size, and whether the seal is pushed fully onto the glass. If those are fine, look at the tray level and the side of the door. The leak may not be starting from the bottom after all.
How do I know what size bottom seal I need?
Measure the glass thickness, the door width, and the gap below the glass. Check the gap in more than one place, as many trays are slightly uneven.