There are several reasons why a cloth nappy can leak. Fit is one of the most common. Always make sure the nappy fits snuggly round the legs and waist and that the inside of the nappy (including any boosters) in all tucked under the waterproof layer. With an adjustable One Size Fits Most nappy, fitting to the legs before the waist can make a big difference - especially if you have a skinny legged baby. If you're using a sized system, leaks can often be an indicator that the nappy being used is either too small, or too large. Also, ensure that your baby's singlet or other clothes aren't tucked into the nappy, otherwise moisture can wick. If you're experiencing problems with the fit of a nappy on your child (especially if it's a nappy with adjustable sizing), please let us know and we'll see if we can help you out with suggestions.
If fit isn't the issue, have a look at your child's nappy after they've experienced a leak. Is the nappy sopping wet as well as the baby? Or is the nappy relatively dry and it's just the baby who's wet?
If the nappy is relatively dry after experiencing a leak, then obviously something is preventing the nappy from absorbing.
The absorbent fabric in a new nappy can take several prewashes before reaching its full absorbency. You know how an old tea towel is better for drying the dishes than a brand new one? It's the same principle. Depending on the fabric it can take between 3 and 6 washes to become fully absorbent.
Detergent residue, nappy rash creams and fabric softeners will all prevent your nappy absorbing properly. Nappy rash creams can clog up the fibres of a nappy's fabric preventing absorption. If you use zinc or petroleum based rash creams on your baby's bottom, always make sure you use a liner to protect the nappy.
Using fabric softener will actually make a nappy repel liquid, so don't use it on your nappies. Using too much detergent, or insufficient rinsing, can lead to a build up of detergent in the fibres of your nappy - it can also cause them to smell. If you suspect any of these is the reason your nappy isn't doing its job, try a strip wash to see if it improves matters.
If the nappy is completely wet the cause of the leakage is insufficient absorbency for the length of time the child is wearing it. This is solved by either changing the nappy more frequently, or increasing the absorbency of the nappy. You can increase the absorbency of a nappy by adding boosters of hemp, bamboo or microfibre. If more absorbency is needed for night time, or if your child has suddenly become a heavy wetter, you might look into more absorbent nappy options or specialised Night Nappies.
Nappies that use microfibre only for the absorbent layer can be subject to 'compression leaks' when the nappy is full and liquid can be squeezed out if the baby is applying pressure to the nappy for a sustained period of time (ie when in a car seat or having a nap). This problem can be solved by adding a bamboo or hemp booster to the nappy - both these fabrics are much better at holding on to liquid (which is why they take longer to dry!).
If the nappy is an older one that you have been using for a considerable period of time and you are suddenly experiencing leaks, it may be the waterproof layer in the nappy has worn out. The PUL in nappies will eventually break down (like all fabrics being worn and washed regularly over a long period of time). This will obviously result in nappies that are no longer waterproof. You can still use the nappy, but it will require a separate cover over the top to be waterproof again. The break down of nappies will be hastened by washing in water over 60 degrees, drying on high heat in a dryer and using bleaches or vinegar in your washing - all of which can damage your nappies and wear them out prematurely (and perhaps void your warranty).
If you're had a look at all these possibilities and you're still stuck on why your nappy is leaking, let us know and we'll see if we can help.