Over time I've had a chance to talk a lot of laundry!
When troubleshooting stink issues, there are three key questions I always cover with people.* If one of these is lacking, ding-ding-winner-winner-chicken-dinner, we've (almost always**) found our culprit.
*These three questions presume you are using a good detergent, are already following our recommended wash routine, and are disposing of the poop properly.
**Just like everything in cloth diapering, it is subjective. These three metrics are the most common areas to consider. There can also be issues with allergies, food sensitivities, skin issues, etc.
Questions to ask Yourself -
Q. Is your first cycle long enough?
Why are we asking this? The first cycle of your wash routine is what is giving your diaper their heavy-duty rinse. If this cycle is too short, or skipped completely, the hot wash+detergent isn't going to work. Want affirmation? Take a look inside your washing machine during the first wash cycle. You are going to see three shades of nasty in there. Now imagine if that was your only wash cycle, and there was detergent trying to get things clean in the midst of all that urine (and EBF poop, if you are still at that age).
A year ago or so, the trend of doing a warm wash cycle instead of cold wash started to take on - the theory being that urine leaves the body at a warm temperature, so a warm rinse will more effectively remove it. I haven't heard enough from customers to support this change, so we still recommend a cold wash to save on energy costs. If the warm wash is working for you, great! Like I mentioned earlier, washing diapers is quite subjective!
Q. Are you using enough detergent?
Yes, there are so many conventional detergents out there that require you to use more than you actually need, which is why you will find the recommendation to use less than their box or bottle advises. However, it has gotten to the point where I'm seeing recommendations for a teaspoon, or half a tablespoon. Folks, you do need some detergent! And the harder the water, the more detergent you are going to need. Strip your diapers to give them a solid rinse, then experiment with using more detergent in your hot wash cycle.
Q. Are you doing an extra rinse at the end?
And not just that rinse that your machine does at the end of your hot wash cycle, but an extra rinse after that? This is what is going to get out the last of the detergent. If you are using a detergent with brighteners of scents (in other words, additives that are designed to stick around after you've washed your clothing), you have to work especially hard to rinse out everything. If your baby has skin of steel, or you've found what I call the 'sweet spot' of detergent amount - just enough to get the diapers clean, but not so much as to requiring an extra rinse - then you might be able to skip this. But if you have a water-stingy HE machine, a baby with extra sensitive skin, hard water or a detergent that doesn't rinse cleanly, well, this extra rinse might be just the thing that solves your laundry frustrations.
Two closing thoughts -
1. All of the above assumes that your washing machine isn't water stingy. Most people with HE-washing machines need to spend a few minutes searching online. If you Google your machine's model + cloth diapers, you will likely find someone else has already done the work for you, finding just the trick to make that HE machine fill up with as much water as possible.
2. Want to geek out more on diaper washing? Check out this post from Bummis (known in the industry for their laundry expertise!)