What Causes Nappies to leak

Whether reusable nappies will leak is one of parents’ greatest concerns. I find that the opposite tends to happen – things like “poonamis” happen often with disposables but are rare with reusables. Yet the myth remains. From what I’ve been able to tell, people readily accept disposables will leak, but are quick to discard (excuse the pun) reusables when this happens.

I’ve had urine leaks too! I’ve been using cloth for well over a year now and don’t really know how many I’ve had, how many I fixed and how many parents I’ve helped along the way. As I’ve learnt, having leaks is not a reason to give up on cloth. There’s ALWAYS a reason why cloth nappies leak. This post is to help you find the reason why your baby’s clothes may be wet. And I say wet because you’re not likely to get a poonami with cloth! I certainly haven’t!

If one of Baby’s S’s nappies leaks, the first thing I do is try to figure out why: was it fit, is the insert dry or saturated, was it at the legs or the tummy, were his clothes touching the absorbent part of the nappy? Then I simply learn and move on. Let’s look at the reasons why nappies may leak and how you can avoid them:

Fit issues

One of the main reasons behind a leaky nappy is its fit – whether it’s too large or too small!

Most one-size or birth to potty (BTP) nappies have rise poppers at the front to make it larger or smaller; the waist will fasten smaller or larger, depending on the baby, which in turn pulls the leg elastics.

Many parents, worried they may hurt their baby, tend to fit the nappy too large or too long which will cause leaks. On the other hand, if the nappy is too tight, it could lead to compression leaks (see below).

A nappy that is properly fit should sit below the belly button and the leg elastics should sit at the groin, as though the baby were wearing pants. How to fix this? Always fit the nappy to your baby’s shape and size. To see how to properly put on a nappy, I recommend you take a look at my YouTube video above.

The photos show a proper fit. You should be able to slide your finger between the nappy and the baby’s leg. However, there shouldn’t be any gaps here. To check for any gaps, lift the baby’s legs (see photos below). You should be able to tuck two fingers at the waist.

The fingers on the right show the way in which the rise poppers should be closed, i.e. from the top down. For a more detailed explanation on this, head over to the Cloth Bum highlight on my Instagram.


Just as with fit issues, having too many inserts or too little can lead to a leaky nappy. Let’s take a closer look … there is a tendency to use extra inserts in the hope nappies can hold for longer, but this is counter-productive as excessive bulkiness will cause a gap between the elastics and legs, or at the tummy which in turn causes … more leaks!

Example of a nappy with too many inserts and, as such, a gap at the legs

In turn, having too little absorbency will also cause leaks, as they won’t be able to hold the baby’s wee. This happens particularly if you only use microfibre.

How to avoid this? Understand the fabric the inserts are made of and use the best combo to maximize absorbency and minimize bulkiness. The best you can do is combine different types of inserts/fabrics, as you can see here

Here I mention another type of leak that has to do with absorbency but usually happens with older babies, or flooders. This type of leak happens when the baby wees in large amounts in one go.

As of a certain age, babies start learning how to control their muscles and tend to wee in larger amounts in one go. How to avoid this? In these situations, it is imperative to combine a rapid absorber, such as microfibre, with a fabric that absorbs slower, but can hold larger amounts of liquid, such as bamboo or hemp. These combos are also useful for babies that wee a lot during the day, the so-called heavy wetters.

Compression leaks

The main reasons behind compression leaks are tight clothes, tight nappies, when babywearing or if the baby is sitting for a long time, for instance when travelling. It is especially frequent when using microfibre inserts alone. This type of insert has the advantage of absorbing liquid fast, but it cannot hold a lot and lends itself to compression leaks. Microfibre acts somewhat like a sponge and will therefore leak when compressed. How to avoid this? Refrain from using microfibre only and combine this fabric with one that holds greater amounts when you leave a nappy on for longer or in one of the abovementioned situations. Buy clothes a size up and there are many brands available that cut their clothes with our fluff bums in mind! When travelling, use inserts that hold more, such as bamboo or hemp.

Contact leaks

Whenever a fabric, such as your baby’s clothes is in contact with the absorbent part of the nappy, it may leak. This happens because if the absorbent material is saturated the wetness will move on to the baby’s clothes unless there is some sort of waterproof barrier to stop this.

This can happen with fitted nappies when combined with PUL pull-up shorts with fleece cuffs. In this case, make sure that the fleece does not touch the nappy, as it is not waterproof and your baby’s clothes may become damp. Also make sure the wrap or cover you’re using is the right size for your baby and that it covers the nappy completely. If you’re using a woolie, it’s important to lanolize it whenever you need to. How can you tell? If the woolie is damp when used or if there is still a whiff of wee after airing it. Any of these are signs the lanolin needs a top-up. For a video on fitted nappies click here and for one on wraps and covers click here.

Both videos have subtitles available.

Likewise, just as with any other nappy, make sure the inside isn’t sticking out of the shell or wrap, for instance at the tummy. How to fix this? Tuck the inside of the nappy inside and rise the outer part of the shell up a bit. Also tuck in any leg elastics that may be showing.

Faulty nappies

This happens more often when you buy preloved, as sadly we can’t always tell what we’re getting, which is why it’s so important that you ask the seller to show you the nappy’s state. A faulty nappy can be:

– Slack elastics. A slack elastic won’t tighten the nappy properly at the legs, causing gaps and thereby leaks. How to fix this: replace the damaged elastics.

– The PUL may be faulty or damaged due to improper use – placing the shell or wrap in a tumble dryer, stuffing the nappy when it’s still warm (for instance from drying in the sun), placing this material under direct sunlight … Some brands may suffer more wear and tear.

Example of a booster folded for boys – at the front of the nappy. For girls, place the booster at the centre or back of the nappy.

Above all, bear in mind that nappies will leak at one point or another – whether disposables or reusables and for the latter, there’s always a solution. Don’t despair!

For another take on leaks, head on over to https://aboderie.co.uk/blog/5-reasons-your-cloth-nappies-are-leaking-and-how-to-fix-them