Rather than go into a (boring) chemistry lesson we will address the reason WHY so many of you have asked us this question: You want to know what it is because the pool guys left a bag of suspicious looking white powder at your house and didn’t tell you why.

DE (Diatomaceous Earth) Pool Filters

While many swimming pool filters use just sand as their primary filtration media, a good number of other pool filters use cloth-like filters covered in diatomaceous earth to filter pool water. The DE powder filters out particles far smaller than sand can remove and the cloth-like material over plastic framework stops large particles and debris from getting through.

Proper Use/Addition of Diatomaceous Earth

First and foremost, consult the manual that came with your filter system to make sure you actually HAVE a DE filter. Then, while you have the manual out, read the sections about starting a DE filter, backwashing a DE filter and cleaning a DE filter. Taking a few minutes right then and there to learn the correct way to care for YOUR filter system will save you innumerable headaches — and possibly a huge amount of money — down the road!

Now that you’ve read the manual you know that you should never operate a DE filter without adding the correct amount of DE through the skimmer, you need to replenish DE powder after backwashing and that once or twice a year you may need to put your filter elements (the ‘cloth’ covered things in your filter) through a process called acid washing (i.e. muriatic acid bath) to dislodge embedded microscopic particulates from their cloth covers…. right?!?

And for the record, you may NOT substitute cyanuric acid for muriatic acid, a chemical you will have to get from your local pool store or hardware store. Careful, though, if using product from a hardware store as it may have a much stronger concentration than its counterparts from the pool supply store!

Oh, and before we forget, many pool supply stores offer acid washing services with 48 hour turnaround times… in case you don’t feel like messing around with caustic chemicals in your backyard. :)