Last updated: 2025-12-17
Expert Tip: This guide is verified by James Liu, our in-house sealing specialist
A 2024 UK study by PlumbNation revealed that 7 in 10 Brits struggle with shower door seal installation.
If you’ve ever muttered “shower screen seal – which way round?” while wrestling with a stiff plastic strip, you aren't alone.
Getting it the wrong way round is one of the most common reasons for shower door leaks.
But here’s the thing: most websites selling seals don’t tell you this. They assume you’ll figure it out.
Already know what you need?
If you've diagnosed the direction and just need a professional-grade replacement, browse our full collection of UK Standard Shower Screen Seals to find the perfect fit 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.
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:
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: The drip rail (the slanted edge) always faces into the shower.
Other seals in this category follow the same rule: Drip rail = Inside.
Shop the Range: Replacement Bottom Seals with Drip Rails – Available for 4mm to 12mm glass.
Why "Standard" Bottom Seals Aren't Always Enough
At SIMBA, many of our shower door bottom gaskets include a free threshold strip—the plastic bar that sits on the floor.
If you’ve installed your seal correctly but still see leaks, your old seal might have perished, or you might be missing this second barrier.
Watch Video:
A Word of Caution on Bulb Seals
You might see these seals sold as "universal," but bulb seals are rarely suited for the bottom of a door .
The Problem: They trap limescale and black mould inside the bulb, making them impossible to clean.
The Result: They perish much faster than a proper single-fin drip rail seal.
Especially in hard water areas like London, bulb seals become a magnet for stubborn limescale.
Instead of a bulb seal, opt for a heavy-duty single fin bottom sweep for a cleaner, longer-lasting fit.
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. Whether they are glued on or clip onto the glass, the rule remains the same:
- Long fin goes inside the shower
- Short fin faces out
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 to seal the gap.
Bonus tip: If the gap is narrow, trim the long fin to match the short one.
So next time you’re holding one of these and wondering “shower screen seal – which way round?”, remember:
3. For 180-Degree Glass (Side & Vertical Seals)
You’ve probably seen seals like the one in the photo – the U-shaped part is rigid (so it grips the glass), and there’s one soft fin coming out the side. This is a classic 180-degree H-shape shower door seal profile, typically used as a vertical side seal to bridge the gap between two glass panels.
Direction: The soft fin should face inwards, into your shower.
This advice assumes your shower door opens outwards – which it should.
According to building regulations (IRC P 2708.1, 2000 edition), all hinged shower doors must open outwards for safety reasons.
The Safety Factor: Why outwards?
Imagine someone slips inside the shower – if the door opens inwards and they’re lying against it, you can’t get in to help.
The Rule: Door opens out = Fin goes inwards.
Explore the Full Range: If your gap needs a different profile, check our complete collection of Vertical Shower Door Seal Strips for all glass thicknesses.
4. Y-Shape Shower Door Seal
These are designed for 135-degree angled glass panels. If your seal looks like a 'Y' and fits at an angle, this is the one you need.
The Rule: The soft fin always 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—the soft fin must always stay on the shower side to deflect spray.
Need a replacement for a diamond-shaped enclosure? Our Y-shape seals are the specialist choice for 135° glass-to-glass joints.
5. Which Way Should a Magnetic Shower Seal Face?
There are two main types of magnetic shower door seals — and yes, direction matters!
1. Flat-top magnetic seals
These are typically a universal fit for 180° straight glass-to-glass or glass-to-wall setups. Since they are symmetrical, there is no "wrong" side.
2. Angled-top magnetic seals
These are designed for specific 90° or 135° corner enclosures. If installed backwards, the magnets won't "snap" together, or your door may jam.
The General Rule:
- The longer edge faces outward (ideal for outward-opening shower doors)
- The shorter edge faces inward
- If your door opens inward, flip that around.
Expert Tip: All SIMBA seals come with clear direction labels to take the guesswork out of DIY.
Find Your Match: Browse our Vertical Magnetic Shower Seals for 6mm, 8mm, or 10mm glass.
🎁 Save 10%: Use code DRYHOME10 at checkout
6. FAQ
Q: Which side of a drip rail seal faces in? A: The slanted drip rail always goes inside the shower screen. [Shop Drip Rail Seals]
Q: Does the long fin or short fin go inwards? A: The long fin faces in; the short fin faces out.
Q: Can I use warm water or a hairdryer to soften the seal? A: Please don’t. While heat makes the plastic easier to push onto the glass, it weakens the "grip" of the seal and causes it to fail much sooner.
Q: Can I use soapy water to help with installation? A: Not recommended. Soap residue can lead to mould build-up and will eventually cloud the transparent look of your seal.
Q: Why won’t my door close after fitting the new seal? A: Check the fin length. If the vertical fin is too long for your gap, the resistance will prevent the door from closing properly. You may need a smaller size.
Q: What should I do if the seal keeps sliding down? A: This happens if the size is wrong or the "U-channel" is too shallow. A quick fix is a tiny drop of clear silicone inside the top of the seal. However, we recommend switching to a SIMBA shower door bottom seal designed for your specific glass thickness.
7. Quick Links to Stop the Leaks
- Folding Shower Screen Seals – Specialist slimline profiles.
- Bottom Bath Screen Seals – High-quality drip rails and gaskets.
- Magnetic Door Strips – Professional-grade water containment.
- Vertical & H-Shape Seals – For side gaps and 180° joints.
8. Final Thoughts
If your seal looks different or isn’t listed, you can usually figure out the correct direction by looking at the soft fins. Still not sure? Don’t risk buying the wrong size.
Email us a photo of your door at info@showerdoorseal.uk – our UK experts will identify it for you!
The SIMBA Promise: We don’t just send you a seal. Every order includes Clear Installation Guides to make your DIY project a success.
Author: Laura Liu & SIMBA Seal Expert
Laura joined SIMBA in January 2017 and has since become an integral part of the team. As a seasoned content manager and seal expert, she oversees website optimization and specializes in crafting informative content about sealing solutions. Her deep knowledge of shower seal technology ensures SIMBA stays ahead in providing value to customers worldwide.