Last updated: 29 April 2026
Expert Tip: This guide has been reviewed by James Liu, SIMBA’s in-house sealing specialist, who works with shower seal design, fitting guidance, and customer troubleshooting.
In our 7-day hard water test in a London bathroom, the incorrectly installed shower door seal leaked in 9 out of 10 water-flow checks around the shower doorway.
If you’ve ever found yourself holding a stiff plastic strip and wondering, “which way round does this shower screen seal go?”, you’re not alone.
Quick answer: on most standard shower doors, the drip rail, longer fin, or soft sealing lip should face inside the shower area. This helps guide water back into the shower tray or bath instead of letting it escape onto the bathroom floor.
Getting the seal the wrong way round is one of the most common reasons a new-looking shower door seal still leaks.
But here’s the thing: many product pages focus on size and glass thickness, but don’t clearly show seal direction.
Already know what you need?
Once you’ve checked the direction and glass thickness, you can browse our shower door seal strip for 4mm to 12mm glass.
In this guide, SIMBA will walk you through how to tell which side faces in, which faces out, and go through common types with simple tips to get it right.
Quick Self-Diagnostic: Did I get it wrong?
Case A: Puddles on the floor, but the seal still looks new?
The drip rail may be facing outwards, which can turn it into a small bridge for water to escape.
Case B: Door is hard to close or springs back?
The vertical fin may be too long, or it may be pressing against the frame in the wrong direction.
1. Bottom Drip Rail Seals: Which Way Round?
Seen this type before? It’s the most common bottom door seal for shower door designs.
That slanted bit on the side (marked 1️⃣) is called the Drip Rail.
Drip Rail Explanation:
The drip rail acts like a slide, directing water back into the shower tray before it even reaches the bottom fin. This reduces the pressure on the soft fin (marked 2️⃣) and prevents puddles on your floor.
A word of advice:
Not every seal strip features a well-designed drip rail. Quality matters for a watertight finish.
Which way round does a drip rail shower screen seal go?
The no-nonsense rule: on most standard shower doors, the drip rail faces into the shower.
Think of the drip rail as a gutter. If the angled drip rail faces out, it acts as a water bridge, guiding water directly onto your bathroom floor.
If yours is worn, split, or no longer gripping the glass, look for a bottom shower screen seal that matches your glass thickness.
Still choosing the right bottom seal? Our shower door bottom seal guide explains the main bottom seal profiles, gap sizes and fitting options in more detail.
Still leaking at the bottom?
If the drip rail is facing into the shower but water still escapes, the problem may not be the seal direction. Check the door gap, tray angle, glass thickness, and whether the door has dropped slightly. In some cases, a threshold strip may help create an extra barrier at the base of the door.
For a full troubleshooting guide, see our article on why your shower door is leaking at the bottom.
A Word of Caution on Bulb Seals
Bulb seals are sometimes sold as “universal”, but they are not always the best option for the bottom of a shower door.
In hard water areas, the hollow bulb can trap water, limescale and mould, making it harder to clean over time. If you’re replacing a bottom door seal, a single-fin or drip-rail style seal is usually easier to maintain.
2. Seal at Bottom of Shower Door with Dual Fins
(Long fin + short fin combo)
They come with two soft fins sticking out – one long, one short. The rule remains the same:
In most cases, the long fin goes inside the shower, while the shorter fin faces outwards as a secondary wiper.
Why? The longer fin stops splashes and directs water back inside. The short one acts as a backup. Together, they work like a mini curtain.
Bonus tip: If the gap is narrow, trim the long fin to match the short one.
3. For 180-Degree Glass (Side & Vertical Seals)
The U-shaped part is rigid, and there’s one soft fin coming out the side. This is a classic 180-degree H-shape seal profile.
Direction: The soft fin should face INWARDS, into your shower.
This advice assumes your shower door opens outwards, which is common for safety and access reasons. Always check your own enclosure design before fitting.
The Rule: Door opens out = Fin goes inwards.
If your door uses this profile, choose a 180° H-shape vertical seal that matches your glass thickness.
4. Y-Shape Shower Door Seal
Designed for 135-degree angled glass panels.
The Rule: In most standard setups, the soft fin faces inside the shower.
Note: This same rule applies if you are using this profile as a frameless Y shape vertical shower door seal on a 90-degree sliding door.
If you have a diamond-shaped or angled enclosure, a Y-shape seal is usually the profile to check first.
Not sure which side seal profile you have? Our vertical shower seal guide explains the common Y-shape, H-shape and F-shape options.
5. Which Way Should a Magnetic Shower Seal Face?
Magnetic shower seals are a little different because direction is not only about water flow — it is also about magnet alignment.
Flat-top magnetic seals are usually symmetrical, so there is often no true “wrong” side. The main thing is making sure the magnets attract rather than repel.
Angled-top magnetic seals are designed for specific 90° or 135° corner enclosures. The General Rule: The longer edge faces outward; the shorter edge faces inward. If your door opens inward, flip that around.
If your existing magnetic strip is cracked, weak, yellowed or no longer meeting cleanly, choose a magnetic shower door seal that matches your glass thickness, angle and closing direction.
Expert Tip from James: We’ve added clear directional labels to SIMBA seals to make fitting easier. With magnetic seals, especially on pivot, folding, 90° or 135° doors, I always recommend checking the angle and polarity before pushing the seal fully onto the glass. Our magnetic shower seal guide walks through those checks step by step.
— James, Founder of SIMBA
6. Frequently Asked Questions
Which side of a drip rail seal faces in?
On most standard shower doors, the slanted drip rail faces inside the shower cubicle. If it faces out, it can channel water onto your floor.
Does the long fin or short fin go inwards?
In most cases, the long fin faces in. It acts as the primary barrier against splashes. The short fin is just a secondary wiper.
Can I use warm water or a hairdryer to soften the seal?
We don’t recommend using strong heat.
Gentle warming may help some PVC seals become easier to fit, but too much heat can distort the profile or weaken its grip. Never use boiling water or high heat. If the seal feels impossible to fit, check the glass thickness before forcing it.
Can I use soapy water to help with installation?
It’s better to avoid it.
Soap, washing-up liquid, oil, or silicone spray can leave residue on the glass and reduce the seal’s grip. Clean the glass edge first, dry it fully, then push the seal on by hand.
Why won’t my door close after fitting the new seal?
This is usually caused by the fin being too long. If the fin is too long, it hits the frame, floor or the opposite side seal, creating resistance.
What should I do if the seal keeps sliding down?
This indicates a glass thickness mismatch. If your glass is 6mm but the seal is for 8mm, gravity will win.
7. Final Thoughts
If your seal looks different from the examples above, start by looking at the soft fins and drip edges. Their job is simple: they should send water back into the shower, not out of it.
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Click here to upload a photo - our experts will mark the correct orientation and send guidance back as quickly as possible, usually within one working day.
Every SIMBA order includes a clear fitting guide, so you can check the seal direction before installation.