Replacing a seal is the cheapest repair in a bathroom and the one most often done twice, because the new profile is bought by appearance and fitted before the cause of the leak has been established. The sequence below is short, and the order matters more than the parts.
Before You Buy Anything
Confirm that the seal is what is leaking. Dry the floor and the outside of the door, run the shower for five minutes and watch where water first appears. Water along the whole bottom line points at the sweep or the base slope. Water at one vertical edge points at a side seal or the hinge line. Water thrown across the room is a spray-pattern issue. Water arriving minutes after the shower is switched off has usually travelled through the floor or wall assembly.
Only the first two are seal problems. Where the diagnosis is unclear, the guide to sealant, seals and coatings explains which product belongs at which joint, and our overview of shower door seals covers how to identify the profile on your door.
Measure the Joint, Not the Old Seal
The old profile is a poor template. It may be a previous replacement, cut short, stretched, or a different shape that was made to work. Measure the door instead: the glass thickness, the height or length of the run, the gap the seal has to close with the door shut at three points, and the way the seal is held - channel, adhesive or compression.
| Measurement | How to take it | What it decides |
|---|---|---|
| Glass thickness | Calipers on the panel edge | Channel or gripping profile size |
| Run length | Along the edge the seal covers | Cut length and number of pieces |
| Gap, door closed | At three points along the joint | Profile depth; fin versus bulb |
| Fixing type | Channel, adhesive or compression | What will stay in place on a moving joint |
If the gap varies by more than a couple of millimetres from one end to the other, the door needs adjusting before a new seal is fitted - otherwise the seal is being asked to close a gap that changes shape as the door moves.
Removing the Old Seal
Pull a channel-held profile out by hand, working from one end rather than the middle. Peel an adhesive-backed seal away with a plastic scraper and an appropriate solvent; avoid blades, which scratch the glass and leave a track that collects minerals. Then clean the channel or the glass face thoroughly: old adhesive residue is why new seals lift at the ends inside a season.
Check the channel for distortion while it is empty. A channel that has opened up will not hold any profile, and in that case the seal carrier needs replacing rather than the seal.
Fitting the New Seal
Dry-fit the profile along its full length with the door closed, and check the door still closes fully against its jamb. A seal that is too deep in section will hold the door slightly open, which moves the leak rather than stopping it - the most common reason a seal replacement appears to fail.
Then cut once, with a sharp blade and a straight edge, and fit from one end without stretching the profile. A stretched seal contracts and pulls away within weeks. For adhesive-backed profiles, apply along the full length in one pass and press with a roller or a firm thumb rather than only at the ends; leave the door open for a few hours so the bond sets uncompressed.
Testing What You Have Fitted
Run the shower for five minutes with the door closed and watch the joint that was leaking. Then open and close the door through its full travel and check that the seal compresses and recovers rather than folding over. On a sliding door, run the panel end to end and confirm the seal does not drag or lift the panel off its guide.
If water still appears, look at the door's adjustment before buying another profile. A door that has dropped changes the gap the seal has to close, and no profile compensates for a panel sitting out of square.
How Often Seals Actually Need Replacing
A seal is a wear item, but most last several years. Replace it when it has hardened and no longer springs back, when it has torn or lost a section, when it will not stay seated, or when the door's adjustment has changed the gap it has to close. Replacing a seal every year usually signals a different problem: a door out of adjustment, a base that does not slope, or a cleaning routine that is degrading the material.
Cleaning is the cheapest way to extend life: rinse the profile after cleaning the glass, keep solvent-based products off the seal face, and leave the door slightly open after use so the seal is not compressed against a wet surface all day. Seal and sweep options for each series are listed in the shower door seals collection. Component test methods are published by ASTM International, glazing requirements for the panel sit in 16 CFR Part 1201, fabrication guidance is published by the National Glass Association, fixing and construction rules come from the adopted code at iccsafe.org, wet-area methods from the Tile Council of North America, and the moisture consequences of a long-running leak from the EPA.
FAQ
Can you replace the rubber seal on a shower door?
Yes, and it is the cheapest repair on the door. Measure the glass thickness, the run length and the gap with the door closed, then fit a profile cut to those figures. Do not match the old seal - it may already be a previous replacement that was trimmed to fit.
Is it easy to replace a shower seal?
Most seals can be changed with the door still hung. Clean the channel, dry-fit with the door closed, cut once to length and seat the profile without stretching. On a sliding door, check the full travel afterwards so the seal does not drag and lift the panel.
How do you replace the plastic strip on the bottom of a shower door?
Pull the old strip out of its channel or peel it from the glass, remove residue, dry-fit the replacement, then cut and fit it from one end. Where the base is beveled or the track is curved, use a flexible fin or bulb profile so it follows the surface rather than sitting on two high points.
Do you silicone the inside or outside of a shower door?
Neither, on a moving joint: silicone belongs at static junctions such as the wall-to-base line, not along a door edge where a profile seal should be doing the work. Sealing a moving joint with silicone creates a tear that holds water, which is worse than no seal at all.
Tell us which joint is leaking and send the glass thickness with the gap measured at three points, and we will confirm the profile and the cut length you need.
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