Last updated: 19 May, 2026
That small line of water by the shower door is easy to ignore the first time. You wipe it away, assume it was just splashback, and carry on.
Then it happens again.
Sometimes the bottom seal is the problem. Often, though, it is only part of the story.
In many UK bathrooms, bottom leaks are caused by a worn seal, poor drip rail direction, an uneven gap, a missing threshold seal, or water that starts from the side but appears on the floor.
This guide helps you identify the real cause before replacing the wrong part.
If you already know the water is escaping directly under the glass and simply want the fitting steps, read our guide on how to seal a shower door at the bottom.
30-Second Check: Is It Really a Bottom Leak?
A frameless shower door bottom leak is usually caused by:
- an old, brittle or yellowed bottom seal
- a drip rail facing the wrong way
- an uneven gap under the glass
- a flat or slightly out-of-level tray
- no threshold seal or water bar
- a side leak that looks like a bottom leak
The puddle is only the clue. The real question is where the water began.
Why Water Leaks from the Bottom of a Shower Door
A shower door leaking at the bottom is rarely caused by one thing alone. Sometimes the seal has failed. Sometimes the door gap is too large. Sometimes the threshold is in the wrong place. Sometimes the tray is sending water towards the door before the seal has any chance of holding it back.
Here are the checks that matter most.
The Seal Is Still There, But It Is No Longer Sealing
A worn bottom seal does not always look broken.
It may still be clipped onto the glass. It may still run across the full width of the door. At a glance, nothing looks especially wrong.
The problem is often in the lower fin. Over time, PVC can harden, curl, lift, or stop sitting neatly against the shower tray. Once that lower edge lifts even slightly, water has a route underneath.
This is why a shower door bottom seal can leak even when it has not fallen off. The strip is present, but it is no longer doing its job.
Look closely at the lower edge. If it is yellowed, stiff, cracked, loose, or curling away from the tray, the seal may no longer be holding water back.
A Few Millimetres Short Is Enough
A shower door seal does not need to be missing completely to fail.
Sometimes it simply stops slightly short of the point it needs to cover. That is especially common at the ends of the door, where the bottom seal meets a vertical seal or finishes near a corner.
The strip may cover most of the door and still fail at the one point that matters.
The same thing can happen when the space under the glass is too large. The seal may fit onto the glass, but the lower fin may never reach the shower tray properly. Water then passes underneath as if the seal were not there.
When checking the lower edge, do not only ask, “Is there a seal?” Ask these instead:
- Does it cover the full width of the door?
- Do both ends reach the correct point?
- Does the lower fin sit close to the tray?
- Does it cover the actual space under the glass?
- Does it meet nearby seals without leaving a small break?
If the bottom of the shower door leaks only in one section, the cut, the end of the seal, or the gap size is often the place to start.
A New Seal Can Still Leak If It Faces the Wrong Way
Some bottom seals have a drip fin or drip rail. Its job is simple: guide water back into the shower area.
If the seal is fitted the wrong way round, it can do the opposite. Instead of sending water back onto the tray, the little fin may push it towards the bathroom floor.
This is one of those faults that looks like a bad seal, but is really a fitting issue. The seal may be new. It may not be cracked. It may still leak.
Check the direction of the fin. It should help water return to the inside of the shower, not lead it out.
If your shower door started leaking from the bottom soon after a seal was replaced, direction is one of the first things to check.
The Gap Under the Glass Is Too Large
A frameless glass shower door needs some clearance at the bottom so it can open and close. That part is normal.
The problem starts when the gap is larger than the seal can cover.
A seal cannot close a space it never reaches. If the glass sits too high above the tray, the lower fin may hover just above the surface instead of pressing against it. Water then passes underneath.
The gap may also change from one end of the door to the other. One side may sit neatly. The other side may be just high enough for water to get through.
This is a common reason why water continues leaking under a shower door even after a new seal has been fitted. The seal may not be the wrong product; it may simply be trying to cover a gap outside its range.
A quick check with a tape measure can help. Measure from the bottom of the glass to the tray at both ends and in the middle. If the distance varies noticeably, that explains a lot.
There Is No Threshold Seal
A bottom seal controls water running down the glass. But if water travels across a flat tray edge, a bottom seal alone may not be enough.
A threshold seal, also called a water bar, creates a small raised barrier on the tray.
The Threshold Is Too Far from the Glass
A threshold or water bar only helps if it sits where the water actually reaches it.
Too far from the glass, and it leaves a channel between the door and the raised strip. Water simply runs through that channel and ends up on the floor.
This is easy to mistake for a faulty bottom seal. The seal may be working. The threshold may also be fitted. They are just not working together.
The bottom seal should guide water back into the shower area. The threshold should act as a second barrier at the entrance. The two need a sensible overlap. They should not sit like separate parts doing separate jobs.
Too close is not ideal either. If the threshold catches the door or rubs heavily against the seal, it can cause a different problem. The useful position is somewhere between those two mistakes.
The Shower Tray Sends Water Towards the Door
Sometimes the door is blamed for a tray problem.
If water naturally sits near the entrance, the seal has a harder job from the start. A very flat shower tray, or one that falls slightly towards the door, can make even a decent bottom seal struggle.
This usually does not look like water spraying from one point. Instead, water slowly gathers near the doorway after each shower. The area around the bottom edge or threshold stays wet.
In older UK bathrooms, the floor or tray may not fall as neatly towards the waste as you would expect. Replacing the bottom seal may help, but it may not fully solve the problem if water keeps travelling towards the door.
In that case, a threshold or water bar may be needed to help direct water back into the shower area.
The Leak May Be Coming from the Side, Hinge, or Corner
Not every glass shower door leaking at the bottom is leaking from the bottom.
Water may start near the hinge, run down the glass, and only show up at the lower edge. It may pass between two glass panels and collect on the floor. It may escape from one bottom corner where two seals meet.
Replacing the bottom seal will not do much if the water is arriving there from somewhere else.
A good clue is the pattern. If the whole lower edge is wet, look at the bottom seal, gap, tray, or threshold. If one corner is always the first wet spot, look at the corner joint. If water appears near the hinge before it reaches the floor, start there.
Fix the starting point, not just the place where the water ends up.
Bottom Leak or Bottom Corner Leak?
A bottom leak and a bottom corner leak can look similar. They are not the same problem.
If water appears along most of the lower edge, the issue is more likely to involve the bottom seal, threshold, bottom gap, or tray fall.
If only one corner keeps getting wet, the joint is the first place to look.
On a frameless shower door, the bottom corner is where several parts can meet: the bottom seal, vertical seal, hinge area, threshold, and shower tray. A small break between any of those parts can let water out.
That does not always mean the full bottom seal needs replacing. Sometimes the end cut is the issue. Sometimes the seal stops short of the corner. Sometimes the nearby vertical seal or hinge-side gap is involved.
One wet corner tells a different story from a wet bottom edge.
Is Water Leaking Under the Seal, Frame, or Track?
People often say, “water is leaking under the shower door”, but that can describe several different faults.
It is worth separating them before choosing a repair route.
Leaking Under the Seal
This usually means water is passing under the bottom seal itself. The seal may be old, lifted, distorted, fitted the wrong way round, or not long enough to cover the actual gap.
Leaking Under the Frame
With a framed shower door, water may appear under the lower frame. That is not the same as a frameless bottom seal problem. It may involve the frame seal, old silicone, or the joint between the frame and tray.
Leaking Under the Track
With a sliding or tracked shower door, water leaking under the shower door track may come from blocked drainage holes, water sitting inside the track, or a failed seal around the lower frame.
A track leak needs a different check from a frameless glass bottom leak. If the water is clearly coming from inside a frame or track, do not treat it as a simple bottom seal issue.
What Not to Do First
When water appears at the bottom of the door, it is tempting to fix it straight away. The quickest-looking repair is not always the right one.
Do Not Seal the Moving Bottom Edge with Silicone
Silicone feels like the fastest answer. On a moving door, it often creates a new problem.
The bottom of the door has to move. Silicone does not.
Silicone belongs on fixed joints, such as where fixed glass meets a wall or tray. For a moving shower door, check the seal, the gap, and the threshold before reaching for silicone.
Do Not Buy a Universal Seal Without Measuring
Many bottom seals look similar online. They are not all designed for the same glass thickness, gap size, or fin length.
A seal can clip onto the glass and still fail to stop water leaking from the bottom of the shower door. Measure first. Guessing usually leads to another replacement.
Do Not Ignore the Threshold Position
A new bottom seal will not solve everything if water is still passing between the seal and the threshold.
Before replacing parts again, check whether the threshold sits close enough to support the bottom seal.
Do Not Trust the Puddle Alone
The puddle shows where the water finished. It does not prove where the leak began.
Once You Know the Cause, Choose the Right Fix
Once you know where the water starts, the next step becomes much clearer.
If the water is escaping directly under the glass, look at the bottom seal first. Is it old, stiff, lifted, facing the wrong way, or too small for the gap?
If water runs across the shower tray edge, the issue may be the threshold position or a missing raised barrier.
If water only appears in one bottom corner, near the hinge, or at a glass joint, do not replace the whole bottom seal straight away. Check the joint, hinge-side space, or neighbouring seal first.
This page helps you find the cause. For cutting, fitting, and repair steps, see our guide: How to Seal the Bottom of a Shower Door.
FAQ
Why is my shower door leaking at the bottom?
It may be a worn bottom seal, a seal cut too short, a large gap under the glass, a threshold set too far from the door, poor tray fall, or water travelling down from the side, hinge, or corner.
How do I stop water leaking under my shower door?
First, find where the water starts. If it starts under the glass, check the bottom seal. If it runs across the tray, check the threshold. If it starts from the side or corner, deal with that leak point first.
Why is my shower door still leaking after replacing the bottom seal?
The new seal may not cover the real gap. It may also be cut too short, facing the wrong way, paired with a threshold in the wrong position, or the leak may be starting somewhere else.
Can I use silicone to stop water leaking from the bottom of a shower door?
Usually not on a moving door. Silicone is useful on fixed joints, but the bottom of a shower door needs to move. Check the seal, gap, and threshold first.
Conclusion
Water at the bottom of a shower door does not always mean the bottom seal has failed.
The real cause may be an old seal, a gap that is too large, a threshold in the wrong place, a tray that sends water towards the door, or water travelling down from the side, hinge, or corner.
The best order is simple: dry the area, test where the water first appears, decide whether it is a true bottom leak, and only then choose the repair route.
If the water is definitely escaping under the glass or beneath the bottom seal, replacing the seal or adding a properly placed threshold is far more likely to work.