A small puddle outside the shower often looks like a failed bottom seal. Sometimes it is. If water is escaping along most of the lower edge of the glass, or the old seal has become yellow, stiff, cracked or misshapen, the bottom seal is usually the first place to check.
Not every leak starts there. In many bathrooms, water escapes from one smaller weak point: the hinge-side lower corner, the end of a fixed screen, a glass joint, or a short section of the tray edge.
That is where a shower threshold strip can help.
A shower door bottom seal fits to the lower edge of the glass and guides water back into the tray. A threshold strip sits on the tray or floor edge and acts as a low barrier where water is already trying to escape.
Quick chooser
Start with the shape of the tray and the position of the leak.
|
Shower layout or leak position |
Start with |
|---|---|
| Large straight frameless screen with a flat tray edge | D510 |
|
Curved tray, quadrant enclosure or awkward hinge area |
PV29 |
| Straight glass with a narrow fitting area and a need for a taller stop | RY3463 |
|
Mixed shape, awkward corner or uncertain tray edge |
PV29 |
As a simple rule, a full-length leak along the bottom of the glass usually points to the bottom seal. A leak from one corner, one end, or a localised area is where a threshold strip becomes more useful.
For the full range, see our shower threshold strips.
Bottom Seal or Threshold Strip?
A bottom seal and a threshold strip both help keep water inside the shower area, but they do it in different ways.
The bottom seal sits on the lower edge of the glass and guides water back into the tray as it runs down the door. A threshold strip sits on the tray edge and acts as a low barrier where water is trying to escape.
They work best as a pair when the leak is localised near an edge, corner, or hinge-side area. The key is contact: the bottom seal fin should meet the threshold lightly when the door is closed. If the two parts sit too far apart, the threshold may look useful but do very little.
For a fuller guide to using these parts together, see our guide on how to seal the bottom of a shower door.
Start with the leak, not the product
Two showers can both be described as “leaking at the bottom”, but the right fix may be very different.
If water is escaping along most of the lower edge of the glass, start with the bottom seal. It may be worn, cut too short, fitted the wrong way round, or no longer flexible enough to guide water back into the tray.
A shower threshold strip is more useful when the leak is localised — for example at the hinge-side lower corner, the end of a fixed screen, or one small section of the tray edge. In those cases, the strip is not replacing the bottom seal; it is protecting the point where water is finding a way past it.
Once the leak point is clear, choosing between a straight, flexible or taller threshold strip becomes much easier. Our shower seal selection guides cover the wider basics if you are still comparing different seal types.
D510: Best for straight screens with a clear tray edge
D510 is the most straightforward option when the fitting area is also straightforward.
It suits clean, straight tray edges, especially on larger frameless screens where the tray edge is flat and open. At around 5mm high, it creates a neat, firm barrier without adding much visual bulk.
The important condition is that it must sit flat.
A rigid strip does not work well on an awkward surface. If the tray edge is curved, raised near the hinge, uneven, or difficult to follow in a straight line, D510 may lift or fail to bond properly in one section. Once that weak point appears, water can still find its way through.
Choose D510 when the edge is straight, flat and open. Do not force it around a curved or uncertain tray edge.
PV29: Better for curves and awkward corners
PV29 is the more forgiving option.
It is a soft, hollow, half-round threshold strip with a height of around 5mm. Because it is more flexible than a rigid strip, it is easier to fit around curved trays, quadrant enclosures, hinge-side areas, fixed screen ends, and edges that are not perfectly straight.
That matters because many leaks hide in small details. From the front, the shower may look simple, but water can travel along the glass, metalwork or tray edge before escaping from one awkward corner.
In that situation, the best solution is not always the tallest barrier. Often, it is the strip that can sit neatly against the problem area without getting in the way of the door.
Choose PV29 when the tray is curved, the corner is awkward, or you are not confident that a rigid strip will sit flat.
RY3463: Useful when you need a taller stop
RY3463 has a different purpose. It is useful when you need a taller water stop on a straight, narrow fitting area.
At around 13mm high, it creates a more noticeable barrier than D510 or PV29. This can help when the leak is concentrated near a side gap, a hinge-side lower corner, or a narrow straight section of the tray.
It should not be chosen by guesswork.
Because RY3463 is taller, it needs to be matched carefully with the bottom seal. If the bottom seal fin is too long, the door may drag or feel stiff. If the fin is too short, it may not reach the threshold at all, leaving water a clear path through the gap.
Before choosing RY3463, measure the gap under the glass and check how the bottom seal will meet the threshold when the door is closed.
The threshold and bottom seal need to meet lightly
A threshold strip does not work simply because it has been stuck somewhere on the tray edge.
For it to help properly, it needs to sit close enough for the bottom seal fin to touch it lightly when the door is closed. That light contact is the important part.
If the threshold and bottom seal fin are too far apart, water can still run through the space between them. The threshold may look installed, but it is not working with the seal.
Heavy contact is also a problem. If the fin is pressed too hard against the threshold, the door may rub every time it opens and closes. Over time, this can make the door feel stiff or deform the soft fin.
As a rough guide, a light overlap of around 3–5mm is usually enough.
For example, if the distance between the bottom of the glass and the shower tray is around 30mm, the correct bottom seal fin length will depend on the height of the threshold strip.
With RY3463, which is around 13mm high, a bottom seal fin of around 18–22mm is usually more suitable. That gives light contact without too much pressure.
With PV29, which is only around 5mm high, the bottom seal needs to reach further down. In that case, a fin closer to 26–30mm may be needed for the seal to meet the threshold properly.
The simple rule is this: The higher the threshold, the shorter the bottom seal fin can usually be. The lower the threshold, the further the fin may need to reach.
Many leaks continue because the bottom seal and threshold strip were chosen separately. They need to meet lightly, not sit apart and not press hard against each other.
How to install a shower threshold strip
Fitting a threshold strip is not complicated, but the position matters.
Before removing the adhesive backing, place the strip where you think it should sit. Slowly close the shower door and check three things:
- the door should open and close normally;
- the bottom seal fin should touch the threshold lightly;
- the ends of the strip should sit close to the wall, glass joint or vertical profile.
Once the position looks right, clean the fitting surface properly. A self-adhesive threshold strip needs a dry, clean surface with no limescale, soap residue, grease, old adhesive or cleaning product residue.
When you are ready to fit the strip, remove the backing and press it firmly into place. Pay close attention to the ends near the wall, corner or glass profile. Even a small gap at the end can let water run behind the strip.
If you are using PV29 on a curved tray or quadrant enclosure, you can gently lift the last few millimetres at the end to create a small stop. Keep this subtle. The strip still needs enough flat contact with the tray for the adhesive to bond properly.
Where a threshold strip is most useful
A threshold strip is most useful when the leak is coming from one small point, rather than along the full bottom edge of the glass.
Common examples include the hinge-side lower corner, the end of a fixed screen, a glass joint, or a small section of the tray edge where water keeps escaping.
In these cases, the bottom seal may still be doing its main job, but water is finding a way past it at the edge. That is where a threshold strip can help create a small barrier in the right place.
Corner leaks are worth checking carefully before adding parts. Our guide to a shower screen leaking at the corner explains how to identify the weak point between the glass, seal and tray edge.
Final choice: D510, PV29 or RY3463?
Choose D510 if the fitting area is straight, flat and open.
Choose PV29 if the tray is curved, the enclosure is quadrant-shaped, the leak is near a hinge or awkward corner, or you are unsure whether a rigid strip will sit flat.
Choose RY3463 if you need a taller water stop on a narrow straight area and there is enough clearance under the door.
The simplest way to remember it is:
Straight, flat edge: D510
Curved, awkward, or uncertain area: PV29
Narrow straight area needing a taller stop: RY3463
If you are still unsure, send us a few photos of the tray edge, glass bottom, existing bottom seal, hinge area and leaking point. We can help you decide whether to replace the bottom seal first, add a threshold strip, and whether D510, PV29 or RY3463 is the closer match.
About the Author
Laura has worked with shower door seals and bathroom sealing products since 2017, focusing on product selection, replacement guidance, and common seal maintenance issues for UK customers.