Help! Why are My Cloth Diapers Leaking?

Do your cloth diapers leak? They shouldn’t. Cloth diapers are designed to keep messes contained, so if you have a leak, something is going wrong somewhere.

So why then are your cloth diapers leaking? Cloth diapers leak when one of seven things go wrong:

  1. The diaper doesn’t fit right;
  2. Baby needs to be changed more frequently;
  3. There isn’t enough absorbency;
  4. The absorbancy that’s there isn’t fast enough;
  5. Minerals, detergent or other products are built-up on the diaper, keeping it from absorbing;
  6. There’s too much pressure on the diaper, causing compression leaks; or
  7. There’s a problem with the waterproof layer

In this post, I’m going to cover each one of those reasons, and then jump into the different types of leaks (at night, though the legs, through the top, etc.) to pinpoint the most-likely causes of your specific leak.

Cloth Diaper Leak Checklist

Click here to get a Leak Checklist PDF that will help you pinpoint the cause of your cloth diaper leak, fast!

How to Keep Cloth Diapers from Leaking

Make Sure the Diaper Fits Right

This is the most common cause of leaks, and the first thing you should check when leaks happen since it’s also the easiest to fix.

Properly fitting diapers should sit flush inside the bikini line crease, with no gaps.

They should also lay as flat as possible around the tummy so that you can fit a few fingers in the top but the diaper still doesn’t shift down even when your little one is busy running all over the place. The top of the diaper should sit just below the belly button and cover the top of the bum completely at all times.

If you’re using a two-piece diaper system, like prefolds, flats, or fitteds, make sure none of the absorbent fabric is sticking out of the waterproof cover, or it will leak.

When adjusting the fit remember that elastics are made to stretch, so worry more about getting a snug fit than putting it on too tight. Often, when adjusting the diaper, we get worried about it being too tight, or worry when we see pink marks after taking a diaper off. Those marks called “sock marks” because they are the same as when you get a few indents on your ankle from snug socks. Sock marks don’t hurt you, and diaper marks won’t hurt your baby as long as they are nice and light and disappear in a short while.

Special note: Sock marks are completely normal, and actually a good thing because you know that diaper is snug. But if those marks are deep, have a white substance in them, or are blistered or bubbled in any way, that’s something else and it should be checked out right away by a paediatrician.

Be Careful Overstuffing Isn’t Ruining Your Fit

If you’re having a hard time getting the diaper to fit in the leg creases no matter how much adjusting you do, make sure you’re not adding too many thick inserts. This is especially a concern if you’re using pocket diapers, which are made to hold a set number of inserts.

Too many inserts pushing the diaper up and off the body can prevent the elastics from sitting where they need to. It can also compress the inserts inside the diaper, causing compression leaks, which we will talk about below.

Make Sure the Diaper’s Elastics are Still Good

No matter how hard you try, if the elastics of your diaper are no longer stretchy enough, you won’t be able to eliminate the leg gaps, at least not without putting the rest of the diaper on too tight.

Here’s a few photos of two diapers. Both are the same brand, the same size, purchased roughly around the same time. There’s only one difference: the elastics of the teal diaper are shot (dried out and crackling when stretched).

It’s no wonder that shot elastics make such a huge impact on fit!

Here are three things to check for if you think the elastics of your diaper might be the cause of your fit and leak problems:

  1. Crunch. If the elastic feels hard or brittle, or if it crackles and crunches when you stretch it, the elastic is completely shot and absolutely needs to be replaced before using the diaper. There’s just no way around this one, as the elastic is so dried out and rotten that it has this crunch to it, it no longer has any use.
  2. Roll. Feel the elastic all around the leg, looking for any spots where the elastic is rolled rather than laying flat inside the seam. If you find rolled spots, or if the entire elastic is rolled this can cause gaps and you should consider changing the elastic.
  3. Stretch. A diaper elastic will stretch and snap back a good two inches or more when fresh, an elastic with not much pop back may also cause problems.

If your elastics are crunchy, rolled, or don’t have much stretch, replacing them may be the key to getting the fit to prevent leaks.

If you have bumGenius diapers, pay special attention to your elastics as bumGenius diapers are notorious for needing elastic replacement regularly.

Make Sure You’re Changing Often Enough

I know, it sounds terrible saying, “Make sure you’re changing them enough.” But sometimes life gets in the way and we don’t realize that baby’s schedule has changed and maybe now they are wetting six times a day instead of four or something.

Making sure to change baby every time they wet is a good start and a good way to prevent leaks and mosture rashes.

Newborns will wet or soil their diaper every two hours or so. That length of time between dirty diapers will lengthen as baby gets older, but how quickly it will depends on the baby, and as we all know, regressions, changes, and all kinds of things can happen to throw a wrench in our routines, so just make sure to give the front of baby’s crotch area a poke every now and then. And no, I’m not kidding… a stiff diaper is a wet diaper!

Make Sure You Have Enough Absorbency

It sounds obvious, but many times leaks happen because baby is releasing XX oz of liquid into the diaper, and the inserts inside the diaper only hold X oz of liquid.

If you’re already changing after every wetting, adding more inserts may be necessary. As baby grows (along with their output), the number of your inserts and boosters may need to grow along with them. When in doubt, add another insert and see.

Make Sure the Absorbency You Have is the Right Kind

Adding more inserts as baby grows is important, but the kind of inserts you’re adding is equally important.

Some types of inserts, specifically natural fibres like cotton, hemp, and bamboo (and the natural-fibre blends, like zorb) are more absorbent than others. On the other hand, some inserts, like microfiber and cotton are faster absorbing.

As you might expect, making sure you’re using high-absorbing, natural fibre inserts is going to help prevent leaks due to volume of waste, but sometimes, for a few babies, the speed of the waste can also be a concern.

Some babies “flood” the diaper, meaning they wet so fast and with so much pressure, that a diaper with only slow-absorbing fibers, like hemp, may not be able to soak it all in fast enough before it floods out of the diaper.

Here’s a handy chart to help you judge if your diapers are pairing the right inserts for your heavy, or fast wetter:

Insert TypeAbsorption AmountAbsorption Speed
Microfiber/Bamboo blend💧💧💧💧💧💧

As your baby grows and changes you may need to start pairing high absorption fabrics with high retention fabrics to match your baby’s output.

There’s Build-up on Your Diaper Causing Repelling

As with all other cloth diaper problems (rashes and smells) buildup can often be the cause. Buildup of detergent, minerals from hard water (calcium and magnesium), or other products like fabric softener and petroleum (found in some diaper creams) will all cause repelling.

If liquid is being repelled off of your diaper (the opposite of absorbing) then it of course will have no where to go but out of the diaper in any small area it can, which is when leaks happen.

If you suspect detergent build-up, you can click here for info on how to test for it and remove it.

If you’ve been using petroleum or fabric softeners on your diapers for a while, you can assume you have build-up and will need to strip your diapers.

If you discover you have hard water after finding your diapers becoming dingy and smelly, stripping may also be required. Information on how and when to strip diapers is here.

There’s Pressure on Your Diaper Causing Compression Leaking

As I mentioned above, overstuffing your diaper is not only a problem because it can lift the leg elastics out of the bikini line, but it can also cause what’s called “compression leaks.”

Just like a sponge, inserts are able to hold much more than most materials, but if you squeeze them, liquid will come out. Making sure that the diaper is not overly squeezed in any way will help prevent compression leaking.

Overstuffing, tight onesies, and even a snug carseat belt pressing baby down for a long period, can all cause compression leaking.

Microfiber inserts are particularly prone to compression leaking over firmer fabrics like hemp and cotton.

To fix compression leaking, just do what you can to lighten the load. Getting thiner, more absorbent inserts like hemp (see the chart above), adding onsie extenders to baby’s onesies (I’ll post a link below for more info), and planning for situations where compression leaks will happen, like the car seat on long trips (I’ll also post a car seat liner) will all help.

We earn a commission if you click this link and make a purchase at no additional cost to you.
09/29/2022 12:01 am GMT
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09/29/2022 12:01 am GMT

There’s a Problem with the Waterproof Layer

Most diaper covers, and shells (meaning the outside of AiO diapers) are made of PolyUrethane Laminate (PUL).  PUL is a fabric (typically polyester but sometimes cotton or polyblend) that’s been adhesive heat laminated on one side to a layer of polyurethane film.

PUL is waterproof, which is why it’s used on the outside of diapers to keep wetness in.

It should come as no surprise then that problems with the PUL will mean leaks.

It’s fairly easy to tell when PUL is the cause of the leak as the wetness won’t seem to come from any of the openings, but instead from random places on the surface of the diaper. The diaper will just be slowly getting wet on the outside.

The three issues that can cause faulty PUL are cracks, delimitation, and just wear and washing of lesser-quality PUL (China cheepie PUL is notorious for this type of slow leaking).

While it’s hard to tell if you’re just dealing with cheap PUL, you can check the PUL for defects. Here are two videos showing you how to check for failing PUL:

A. Cracking (video courtesy of The Towers)

B. Delamination (video courtesy of Darlings Downunder)

If your PUL is cracked, delaminated, or leaking unfortunately there’s no saving it and it’s time to retire it from diaper duty.

So now that we know all the ways we can fix cloth diaper leaking, let’s take a look at some specific types of leaks. This will help us narrow down which causes are the likely suspects, so we don’t have to waste time fixing things that aren’t broken (and washing clothes that get accidents on them).

Why is My Cloth Diaper Leaking from the Legs?

If your cloth diaper is leaking from the legs, the most likely cause is a poor fit, overstuffing, or shot elastics.

First, check the fit of your diaper to make sure those elastics are firm in the bikini line crease. If not, try to adjust the fit, check the elastics, and make sure you’re not overstuffing the diaper with too many inserts.

If your diaper is as snug to the bikini line as you can get it, but you’re still getting leaks from the legs, it may be a slow absorption or buildup issue causing the liquid to not be absorbed into the diaper fast enough, allowing it to get through even the tiniest of openings between the leg and diaper.

If you’re only using slow absorbing inserts, like hemp and bamboo, try adding a faster absorbing insert (see above for details).

If, however, you are using microfiber, cotton, or zorb, do the swoosh test outlined above to make sure you don’t have buildup on your diapers that would prevent them from absorbing.

Why is My Cloth Diaper Leaking from the Top?

If the leak is coming from the waist or back at the top of the diaper, the cause is likely fit, or you have a boy and his penis is pointing up.

If you have a boy, make sure he’s pointing down before you do up the diaper. If you’re sure he is down, or you have a little girl, check that the diaper is sitting nice and high on the waist and the entire bum area is covered.

If none of those things are the problem, check that you have enough absorbency added, and that there’s no buildup on your diapers.

Why are My Cloth Diapers Leaking through the PUL?

If your cloth diapers are leaking right through the PUL cover layer, there’s a problem with that waterproof layer.

Check for cracks or delimitation using the methods in the videos above, and/or try a higher-quality diaper.

Why is My Cloth Diaper Leaking at the Stitching (Seams)?

A cloth diaper leaking at the seams is usually caused by a PUL issue.

If your diaper is brand new, it could be that it was never “sealed.” To seal it, dry it in a hot dryer (I know, I’m contradicting my dryer advice here, but it will be just this once) for about 15-20 min. This is because the needle pokes by the sewing machine create holes that need to be sealed. Most larger cloth retailers sell their diapers pre-sealed, but occasionally something may happen, and smaller cloth diaper operations may not pre-seal their diapers.

If the diaper still leaks at the seam after drying on high-heat, it’s likely the start of a different PUL problem, and you’ll want to check for cracks or delimitation using the methods in the videos above.

Why are my Cloth Diapers Leaking at Night?

Night time leaks are some of the most frustrating because not only do you have to change baby, but you also have to change bedding, and maybe wash that lovey or other items in the bed as well. Ugh.

Night time leaks are almost always due to not having enough absorbency for the long stretch of time your baby is sleeping (or that long stretch you’re hoping to get to one day, anyway). Unfortunately, those same diapers that get you through the day probably won’t work overnight.  

I’ve written full instructions on how to diaper successfully overnight here. In that article, I also share the three diapers (and one prefold hack) that can get you through the night.

What if My Cloth Diaper Leaks When Baby Sleeps on Their Side

If your overnight diaper is only leaking when baby sleeps on their side, first, do make sure you have enough absorbency added, but also check the fit and consider either switching to a fitted diaper or adding some fast absorbing material to the diaper.

I suggest the fitted diaper and the faster absorbing insert because it may be that baby is wetting so quickly that if that wetness is not sitting on the back of the diaper, but instead only on the thin side, it doesn’t have time to be absorbed. Fitted diapers have absorbency built in to the whole diaper, including the side and around the hips. Similarly, adding a faster absorbing material may help get the wetness absorbed into the whole diaper before it escapes out the thin side.

If you have a boy, also take the time to make sure he’s pointed down and not to the side.

Don’t Forget the Freebie

Wow, you read this whole article? You are awesome! Now that you know all there is to know about cloth diaper leaks, don’t forget to get the one-page leak checklist if you haven’t already.

Keep it handy and whenever you get a leak you can take a look at the cheat sheet to find the causes listed in order. Use it to help you recall what you learned here and fixing those leaks with be a breeze!

Need More Help?
If cloth diaper information is becoming overwhelming, or if you’re having trouble with your cloth diapers that you can’t seem to work out, check out the Cloth Diaper Wash & Care Handbook.

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