Avoiding Common Flexseal Coupling Mistakes: What You Need to Know Before You Connect
Flexseal couplings are a brilliant bit of kit. Whether you're connecting clay to plastic, repairing a cracked drain, or adapting two odd-sized pipes, they make what used to be a nightmare job quick and easy. But even with something so straightforward, it’s surprisingly easy to get it wrong and those little mistakes can lead to big problems down the line.
Here’s a practical guide to help you avoid the most common slip-ups and get your Flexseal installation right the first time.
1. Grabbing the Wrong Size
Let’s be honest: we’ve all been guilty of eyeballing a pipe and thinking, “Yeah, that’ll do.” But Flexseal couplings are all about precision, they’re designed to fit snugly, not just kind of fit.
Tip: Always measure the outside diameter (OD) of the pipes you’re connecting. Don’t go by guesswork or just the pipe type. Pipes with the same name can have different sizes depending on the material or age.
2. Overtightening the Bands
This one’s common: you're worried about leaks, so you crank down on the metal clamps like you’re tightening wheel nuts. The problem? You can overdo it, and damage the rubber or even deform the pipe.
Tip: Use a torque wrench if you can, and aim for the manufacturer’s recommended setting (usually around 6Nm). Tight enough to seal, not so tight it bites.
3. Skipping the Clean-Up
It’s tempting to slap on the coupling and move on, especially if you're working in a trench or the rain’s coming down sideways. But if the pipe surface is filthy, oily, or flaky, you’re not giving the coupling a fair shot.
Tip: Give the pipe ends a proper wipe down. A wire brush and a rag with some soapy water work wonders. Smooth surfaces = solid seal.
4. Not Lining Things Up Properly
Flexseal couplings are flexible but they’re not magic. If your pipes are off at a weird angle, that rubber sleeve is going to be under stress from the start.
Tip: Make sure the pipes are aligned as straight as possible. Use supports or shims if needed. A little misalignment is fine, but don’t push your luck.
5. Using the Wrong Coupling for the Job
Not all Flexseal couplings are made equal. Some are for underground drainage, some for above-ground, some are reinforced for pressure. If you’re trying to use a basic coupling on a pumped line, you might be in for a soggy surprise.
Tip: If the system is under pressure (like from a pump), use a shear banded or high-performance coupling. Always match the coupling to the job.
6. Backfilling Before Testing
We get it—you want to get the hole filled and the job ticked off. But rushing to bury your work before checking for leaks can come back to haunt you.
Tip: Run water through the pipe before you bury anything. Just a few minutes of testing can save hours of digging later.
7. Ignoring Approvals and Standards
This one's especially important on jobs that need sign-off. If you're using a coupling that isn't approved for the application, it could cause issues down the line—even if it works perfectly.
Tip: Check that the coupling has the right marks—like Kitemark or CE—depending on where and how it’s being used. Better safe than sorry.
Wrapping Up
Flexseal couplings are designed to make your life easier, and they do—when used properly. If you take a few extra minutes to size up correctly, prep the pipework, and double-check your fitting, you’ll end up with a clean, leak-free connection that lasts.
Quick Recap:
✅ Measure the outside of the pipes
✅ Don’t overtighten the bands
✅ Clean the pipe ends properly
✅ Align pipes straight before clamping
✅ Use the right type of coupling for pressure or underground use
✅ Always test before you backfill
✅ Stick to approved fittings when required
Take your time, do it right, and Flexseal will do the rest. To view our full range feel free to view www.mp-products.co.uk